ALBERT

Notes: Metal phthalocyanines (M = Cu, Ni, Co) 3-5 bearing four 16-membered diazadithia macrocycles at the peripheral positions were prepared. Detosylation with concentrated sulfuric acid afforded products containing both sulfonated groups on the aromatic rings of the macrocyclic substituents which are excellently soluble in water and donor sites for binding four CuII ions to give a pentanuclear complex.

Notes: Ab initio MO calculations at the QCISD(T)/6-311++G(3df,2p) + ZPE level show that the thionitrosyl chloride ion, ClNS+•, is 36 kJ/mol more stable than the thiazyl chloride ion, NSCl+•, whereas neutral NSCl is 77 kJ/mol more stable than ClNS [IEa (ClNS) = 9.2 ± 0.3 eV, IEa (NSCl) = 10.5 ± 0.3 eV]. Mild flash-vacuum pyrolysis of the thiazyl chloride trimer (NSCl)3 followed by electron impact ionization resulted in the formation of [N,S,Cl]+• ions (m/z 81). The fragments observed in the CA spectrum of these ions indicate the formation of both NSCl+• and ClNS+• ions. A very weak recovery signal is observed in a neutralizationreionization experiment. This signal is tentatively assigned to the neutral thionitrosyl chloride.

Notes: 4-Butoxynitrobenzene reacts with [Hg(O2CCF3)2] and LiCl to give [Hg(R)Cl] [R = C6H3NO2-3, OnBu-6 (1)] which is symmetrized by Me4NCl to give [HgR2] (2), the crystal structure of which has been determined. The reaction of 2 with Me4N[AuCl4] affords Me4N[Au(R)Cl3] (3) by a facile transmetallation process. Complex 3 reacts with PPh3 (1:1) to give cis-[Au(R)(PPh3)Cl2] (4). The diaryl complex [-Ph-2)(R)Cl] (5) is obtained by reaction of 3 with [Hg-(C6H4N=NPh-2)2] through a second transmetallation reaction. Complex 5 and PPh3 (1:1) give [AuClPPh3] and the C-C coupling biphenyl RC6H4N=NPh-2 (6).

Notes: The synthesis and coordination chemistry of sulfenic, thiosulfinic, and thiosulfonic acid anions are reviewed. Different approaches, which yield the platinum(II) and ruthenium(II) complexes containing the anionic sulfur(0), sulfur(II), and sulfur(IV) oxid ligands, are described. The oxidative addition of thiosulfinates or N-sulfinyl phthalimides to platinum(0) complexes L2Pt(C2H4) [L = PPh3, 1/2 PPh2CH2CH2PPh2, 1/2 (R,R)-(-)-DIOP, 1/2 (C5H4PPh2)Fe(C5H4PPh2) leads to sulfenato complexes; those of N-thiosulfinyl phthalimidies or trisulfid 1-oxides afford the thiosulfinato complexes. Moreover, the reactions of CpRu(PPh3)(L)(SH) (L = CO, PPh3) with N-sulfinyl phthalimides forming the thiosulfinato moiety, are reported. The spectroscopic, structural and chemical properties of these complexes are discussed.

Notes: The cationic iron (alkynyl)aminocarbene complexes [Cp(CO)2Fe(C(NHR)C≡CSiMe3][PF6], (R = C6H5, p-CH3C6H4) 1 derived from aromatic amines smoothly react with cyclopentadiene in dichloromethane to yield the cycloadducts 2. No reaction was observed for complexes derived from sterically demanding aliphatic amines, like L-alanine tert-butyl ester. For comparison, the alkynyl-substituted acyl iron compounds Cp(CO)2Fe(C=O)C≡C̊ (R = SiMe3, C6H5) 3 were investigated, requiring TiCl4 catalysis to undergo the cycloaddition reaction. The structures of the cycloadducts 4 were determined by X-ray crystallography.

Notes: Treatment of (cdt)Ni (cdt: cyclododeca-1,5,9-triene) with 2 equivalents of 2-methyl-4-trimethylsilyl-3-butyn-2-ol leads to the selective formation of the homoleptic complex (alkyne)4Ni3 (compound 3), which can be isolated in excellent yields. The solid-state structure of 3 exhibits three Ni centers, forming a bent Ni3 chain connected by two bridging alkynes. The other two alkynes are terminally coordinated. Additionally, the trimeric units are stabilized by three intramolecular hydrogen bonds. Two intermolecular hydrogen bonds connect the trimeric units to form a polymer rope. According to the 13C- and 1H-NMR spectra in THF the structure of the complex 3 in solution is very similar to that in the solid state. The reaction of 3 with some alkynediols and with 2,5,5-trimethylhex-3-yn-2-ol affords compounds of the type (alkyne)2Ni. Cot (cot: 1,3,5,7-cyclooctatetraene) converts 3 into [(cot)Ni]2, which in turn reacts with 2,5-dimethylhex-3-yne-2,5-diol to form the dimeric complex (alkyne)2Ni2(cot) 6. X-ray analysis of 6 reveals a very symmetrical structure in which cot connects both Ni(0) centers at opposite sides of the ring system.

Notes: The SO2 coordination mode at the rhodium complex [ClRh(P∼O)()] (1) [ = η2(O,P)-chelated Cy2PCH2CH2OCH3 ligand; P∼O = =1(P)-coordinated] is controlled by the hemilabile ligand Cy2PCH2CH2OCH3 and shows a dependence on the polarity of the solvent. In polar organic solvents (e.g. acetone) the addition of sulfur dioxide results in the formation of a trigonal-pyramidal oriented SO2 group in [ClRh(η1-SO2)(P∼O)()] (2a). However, in nonpolar media (e.g. n-hexane) a trigonal-coplanar geometry of the SO2 unit in [ClRh(η1-SO2)(P∼O)2] (2b) is favored.

Notes: Pentacarbonyl(allenylidene)chromium and -tungsten, [(CO)5—M=C=C=CR2] (M=Cr, R=C6H4CH3-p(1a), C6H4OCH3 (1b); M=W, R=C6H4CH3-p (1c), react with the alkynyl complexes [Cp(CO)2Fe—C≡CR′] (R′ = nBu (2), Ph (4)), [Cp*(CO)2Fe—C≡CnBu] (6), [Cp(CO){P(OMe)3}-Fe—C≡CnBu] (8) and [Cp(PPh3)Ni—C≡CnBu] (10) by cycloaddition of the C≡C bond of the alkynyl complexes to the Cα=Cβ bond of the allenylidene ligand to give 3a-c), (5), (7), and respectively. The cycloaddition is highly selective. The spectroscopic data of these 1,3-heterobinuclear complexes indicate a delocalized π-system (M=Cr, W; Y=[Fe(CO)2Cp], [Fe(CO)(P{OMe}3)Cp], [Fe(CO)2Cp*], [Ni(PPh3)-Cp]). X-ray structural analyses of the compounds 3a, 9a, and 11c reveal a “butterfly” conformation of the four-membered ring. Its puckering angle is 142° (3a), 152° (9a), and 151° (11c). All Complexes exhibit a moderate to strong negative solvatochromic behavior. The extent of the solvatochromic effect depends on [(CO)5M] and Y and considerably decreases when C=CR2 is replaced by e.g. CMe2.

Notes: Optically active alcohols (ee ≥ 98%) such as 1-phenylpropanol, 1-(2-naphthyl)ethanol, 1-tetralol, and 1-indanol were transformed into diethyl phosphates 7a-d. sBuLi/TMEDA  -  induced phosphate - phosphonate rearrangement in diethyl ether furnished tertiary α-hydroxyphosphonates 8a-d of high enantiomeric purity (ee 94-98%) in yields of 43-83% with retention of configuration. The enantiomeric excesses were determined by using homochiral t-butyl(phenyl)phosphinothioic acid as chiral solvating agent.

Notes: The cationic tetracarbonyl complex cis-[Mn(CO)4-(S2CPCy3)]+ undergoes addition of hydride ion to the central carbon of the S2CPR3 ligand to afford, after spontaneous dimerization with loss of CO, the dimer [Mn2(CO)6{μ-S2C(H)PCy3}2] (5a), which was characterized by analytical and spectroscopic methods as well as by X-ray diffraction. In the molecule of 5a each S2C(H)PCy3- ligand is coordinated to one manganese in an η2-S,S′ chelate fashion, and one sulfur of each ligand serves as a bridge to bind the other manganese atom, thus forming a distorted Mn2S2 square. This appears to be a very stable arrangement. Compound 5a can be more easily prepared by treating the perchlorato complex [Mn(CO)3(S2CPCy3)(OClO3)] (2a) with NaBH4. This procedure is general and can be used for the preparation of several derivatives containing either manganese or rhenium [M2(CO)6{μ-S2C(H)PR3}2] 5a-d. The reaction of cationic tricarbonyl complexes [M(CO)3(S2CPR3)(PPh3)]PF6 (M = Mn, Re) with NaBH4 produced the same dimers 5a or 5c by displacement of the PPh3 ligand. Treatment of the dimer 5a with excess PEt3 or P(OMe)3 leads to the cleavage of the bridges and loss of one CO and the PR3 group from the S2C(H)PR3 unit to afford ultimately the dithioformate complexes [Mn(CO)2(S2CH)(L)2] [L = PEt3, P(OMe)3].

Notes: Organo-Zinc Phosphaneiminato Complexes with Heterocubane StructureThe organo-zinc heterocubanes [ZnR(NPMe3)]4 with R = CH3 (1) and n-C4H9 (2) were prepared by the reaction of [ZnBr(NPMe3)]4 with MeLi and nBuLi, respectively, in hexane solution. In a similar reaction of nBuLi with [ZnI(NPMe3]4 the phosphaneiminato complex [Zn4I(nBu)4(NPMe3)3] (3) is formed. 1-3 were characterized by IR, NMR and MS spectroscopy, and by crystal-structure determinations. 1 and 2 possess heterocubane structures in which the zinc atoms are linked via μ3-N bridges of the phosphaneiminato groups, and all bond angles in the Zn4N4 core are close to 90°. A distorted heterocubane structure is observed for 3 with one of the NPMe3 moieties replaced by an iodine atom.

Notes: Sulfoxonium ylides 3a-h were synthesized by silylation of the cyclic methylene disulfones 1,3-dithietane 1,1,3,3-tetraoxide (1) and 1,3,5-trithiane 1,1,3,3,5,5-hexaoxide (4) with the silylating agents silyl nonafluorobutanesulfonates. The structure and constitution of the ylides were established with 1H-NMR, 13C-NMR, 29Si-NMR spectroscopy, mass spectrometry, and elemental analysis. On the route to the sulfoxonium ylides a new class of unsaturated disulfenes 7, 8, 12, 13 of 1 and 4 were synthesized via Knoevenagel and substitution reactions. Dianions of newly formed alkyl disulfenes 16a, b, e, f, and the trianion 17 were prepared and characterized by 1H-NMR and 13C-NMR spectroscopy and compared with the results of the ylides.

Notes: Addition of CS2 and Other Heteroallenes to the 16-Electron Osmium(0) Complexes trans-[OsCl(NO)(PiPr2R)2]The coordinatively unsaturated 16-electron compounds trans-[OsCl(NO)(PiPr2R)2] (1: R = iPr; 2: R = Ph) react with CS2 and COS to form the 1:1 adducts [OsCl(NO){κ2(C,S)-S=C=S}(PiPr2R)2)] (3, 4) and [OsCl(NO){κ2(C,S)-S=C=O}-(PiPr2R)2] (6, 7), respectively. While compounds 3, 4 are inert toward PMe3, the Os(COS) complexes 6, 7 react with tri-methylphosphane by abstraction of sulfur to give (OsCl(NO)-(CO)(PiPr2R)2] (8, 9). From 1 or 2 and phenylisothiocyanate the corresponding 1:1 adducts (OsCl(NO){κ2(C,S)-S=C=NPh}(PiPr2R)2] (10, 11) are obtained. Protonation and methylation reactions of 10 (R = iPr) with HBF4 or CF3SO3Me lead, by addition of the electrophile to the C=N nitrogen atom, to the formation of [OsCl(NO){κ2(C,S)-S=CNHPh}-(PiPr3)2]BF4 (12) and [OsCl(NO){κ2(C,S)-S=CN(Me)Ph}-(PiPr3)2]CF3SO3 (13). Treatment of 1 with diphenylketene yields [OsCl(NO){κ2(C,O)-O=C=CPh2}(PiPr3)2] (14). The X-ray structure analyses of 10 and 14 confirm the coordination of phenylisothiocyanate via S and C and of diphenylketene via O and C, respectively.

Notes: 8-Lithioquinoline reacts with 2,3,4,5-tetramethylcyclopentenone to give 8-quinolylcyclopentadiene (1/2) after acidic workup and treatment with ammonia. Two of the possible three isomers are formed; the acidic protons on the Cp rings show unusual downfield shifts in the 1H-NMR spectra. Treatment with strong bases led to the intensely coloured anionic 4 which was converted into the trimethylsilyl derivative 5. This is a suitable starting compound for the trihalotitanium and -zirconium compounds 6 and 7. The two complexes were investigated by crystal structure analyses. In both cases the quinolyl nitrogen atom is coordinated to the metal.

Notes: On the Silaethene tBu2Si=C(SiMe3)2, and the Structure and Reactivity of Its [4 + 2] Cycloadduct with Ph2C=OFrom tBu2SiF—CLi(SiMe3)2 by LiF elimination only Me2Si= C(SiMe3)(SiMetBu2) (1b) instead of tBu2Si=C(SiMe3)2 (1a) is isolated. With benzophenone, silaethene 1b (from its THF adduct 1b · THF) forms at -78 °C a yellow [4 + 2] cycloadduct (5) and a colorless [2 + 2] cycloadduct (6). With increasing temperature 5 transforms into 6, and 6 transforms -more slowly - into the yellow [4 + 2] cycloadduct (7) of 1a and Ph2CO. It follows from this that the migration equilibrium 1a ⇄ 1b really exists. The structure of 7 shows a planar —O—CPh=C6H5-framework with the cycloadded atoms Si and C from -tBu2Si—C(SiMe3)2- located above the plane. The =C6H5—C bond (1.62 Å) is exceptionally long. 7 is a source for 1a which is trapped by acetone (formation of an ene product) and by benzaldehyde [formation of a [2 + 2] cycloadduct, unstable against cycloreversion into PhHC=C(SiMe3)2 and tBu2SiO-containing substances]. Reaction of 7 with trimethylsilyl azide, less reactive than acetone or benzaldehyde, leads - by way of 1a which transforms into 1b - to a trapping product of 1b (formation of a [3 + 2] cycloadduct, unstable against transformation into (RMe2Si)(Me3Si)CN2 with R = (Me3Si)2N, or cycloreversion into (tBu2MeSi)(Me3Si)CN2 and Me2SiNSiMe3-containing substances). Reaction of 1b or 1b · THF with acetone leads only to an ene reaction product of 1b. This means, that only undetectable amounts of 1a or 1a · THF are in equilibrium with 1b or 1b · THF. A minor substance which is shown by NMR at low temperatures besides 1b or 1b · THF is interpreted as a rotamer of 1b or 1b · THF.

Notes: In the presence of Lewis acidic derivatives of group 13 elements, phosphaalkynes 7 undergo spirocyclotrimerization with incorporation of the corresponding Lewis acids to form 10a-f. Scope and limitations of this novel cyclooligomerization process are examined. Starting from the spirocyclotrimer 10a reaction with the Lewis base dimethyl sulfoxide, we have in hand for the first time a method for the selective generation of two isomeric triphospha Dewar benzene derivatives (18, 19). Both can be trapped efficiently by further reaction with the phosphaalkyne to furnish the two novel phosphaalkyne cyclotetramers 20 and 21, both still possessing a phosphorus-carbon double bond. In the case of 21, further functionalization of the phosphaalkene unit is possible by [3 + 2] cycloaddition with a nitrile oxide (→ 23).

Notes: The substituted 6-hydroxy-trans-3-hexenoic acids 2a and 2b are prepared by an organometallic template reaction involving a sequence of CC coupling reactions between a CO2 equivalent, butadiene, and 3-cyclopenten-1-one or 3,4-diphenyl-3-cyclopenten-1-one, respectively. In the crystal 2a assembles to form an infinite ribbon-type structure, exhibiting an alternating array of 12 and 18 atom-containing loops. The former are each constructed by an alternating CO2H/OH/CO2H/OH sequence, originating from four different monomeric units, that are linked together by means of hydrogen bonds. Two complementary ribbons of 2a are connected by van der Waals interactions to form staples that constitute the microscopic building blocks of the true (2a)n structure in the crystal. Stacks of cyclopentene π bonds are oriented inside the columnar structure of 2a. Acid 2b also forms a related ribbon-like assembly in the solid state. Here the bulky 3,4-diphenylcyclopentadienylidene moieties are oriented laterally at the ribbons, and van-der-Waals interactions with adjacent ribbons construct a three-dimensional hydroxyhexenoic acid network.

Notes: Some dithioxophosphoranes 3 stabilized by intramolecular coordination with a dialkylamino group were prepared, and their structures were analyzed by X-ray crystallography involving [2,4-di-tert-butyl-6-(isopropylmethylamino)phenyl]- (3c), {2,4-di-tert-butyl-6-[(dimethylamino)methyl]phenyl}- (3f), and {2,4-di-tert-butyl-6-[2-(dimethylamino)-1,1-dimethylethyl]phenyl}dithioxophosphorane (3h). The bond between the phosphorus atom and the aromatic ring is flexible and the angle narrows with decreasing ring size of the intramolecular coordination. The 31P-NMR signals are shifted to higher field with increasing ring size of the intramolecular coordination or strength of coordination. Similarly, the corresponding diselenoxophosphoranes 4 were prepared. Both their 31P- and 77Se-NMR signals are shifted to higher field with increasing contribution of intramolecular coordination.

Notes: Indium(III) and tin(IV) thiocarboxylates were prepared and characterized on the basis of their IR, 13C- and 19Sn-NMR data. Indium tris(thiobenzoate) (1) decomposes into a sulfido complex In (S)[S(O)CPh] (2a). The corresponding tris(thioacetate) In[S(O)CMe]3 is thermally too unstable to be isolated. The anionic tetrakis complex [Et3NH]{In[S(O)CPh]4} (3) was characterized by X-ray crystallography which revealed a distorted tetrahedral coordination at the In atom. X-ray diffraction analysis of the complexes BuSn[S(O)CPh]3 (4) and Cl2Sn[S(O)CPh]2 (7) showed distorted tetrahedral and cis-octahedral structures, respectively.

Notes: The coordination behaviour of ligands having the same basic constitution RN=NC(=X)R′ (X = O, NR″, S) in their tripod cobalt derivatives has been analyzed. The ligands themselves may be considered as neutral heterodiene compounds and are in this respect vinylogues to diazenes RN=NRy′. Two- electron reduction of these neutral species results in dianionic heterosubstituted heteroolefins RN- -N=C(X-)R′. Due to their redox ambiguity the oxidation state of the metal M in chelate complexes is not a priori evident. Compounds tripod [5: X, R′ = O, Ph; 6; (X, R′) = (py); 7: X, R′ = S, NH2] are best described as containing low-spin Co(III) and dianionic ligands. Co(II) species are obtained with diethyl azodicarboxylate EtOOCN=NCOOEt as the ligand. In the mononuclear compound, with only one nitrogen and one carbonyl oxygen of the ligand acting as donor groups, the neutral ligand is coordinated to give the high-spin cobalt(II) species tripod (8). In the dinuclear compound 9 with both of the nitrogen atoms and carbonyl groups involved in coordination the dianionic ligand bridges two high-spin cobalt(II) centers to give tripod (9) as a derivative with two fused five-membered chelate rings. In addition to the conventional analytical techniques X-ray structure analyses, cyclovoltametric measurements, magnetic susceptibility and ESR data are used to characterize the compounds.

Notes: Transition-Metal Stannyl Complexes, 10 - Molybdocen and Wolframocen Derivatives with Two Different Main-Group-4 LigandsReactions of Li[Cp2MSnPh3] (M = Mo, W) with CH3I, BuBr, PhCH2Br, PhC(O)Cl or Br(CH2)nBr (n = 4,5) yield Cp2M(R)SnPh3 [R = CH3, Bu, CH2Ph, C(O)Ph, (CH2)nBr], while tBuBr or CH3C(O)Cl give the hydrido complexes Cp2M(H)SnPh3. A silyl stannyl complex is only obtained from Li[Cp2WSnPh3] and Me3SiOSO2CF3, but not with Me3SiCl or from the anionic Mo complex. In contrast, the reactions of chlorostannanes provide the bis(stannyl) complexes Cp2M(SnR′3)SnPh3 or Cp2M(SnR′2Cl)SnPh3. R/Cl exchange at the tin atom is observed when an excess of the chlorostannane is used. Upon reaction of Li[Cp2MSnPh3] with Ph3PbCl only Cp2M(PbPh3)SnPh3 is formed, while a mixture of Cp2M(PbMe3)SnPh3 and Cp2M(PbMe2Cl)SnPh3 is obtained with Me3PbCl due to redistribution reactions. The structures of Cp2W(SnPh3)C(O)Ph, Cp2W(SnPh3)SntBu2Cl and Cp2W(SnPh3)PbMe2Cl were determined by X-ray structure analyses.

Notes: Pentacarbonyl(thiobenzaldehyde)tungsten und pentacarbonyl(selenobenzaldehyde)tungsten (1a and 1b) undergo a thermal [2 + 2] cycloaddition with several vinyl ethers to give highly substituted transition metal-coordinated thietanes and selenetanes. The addition is highly regio- and stereospecific. The products undergo acid-catalyzed rearrangements, which lead to thermodynamically more stable diastereomers of the thietanes and selenetanes. The stereochemistry of both addition and rearrangement was established by reaction of deuterium-labeled vinyl ethers and by reaction of the cis and trans isomers of ethyl propenyl ether. The crystal structure of the bicyclic addition product of 1a and 3,4-dihydro-2H-pyran is reported.

Notes: Highly substituted pyrazolylborate ligands TpR,Me were used to limit the coordination number of zinc towards cysteine- and histidine-derived coligands. Monodentate thiolate attachment (→ 1a-f) was achieved with N- and C-protected cysteine, monodentate carboxylate attachment (→ 3) with N-protected histidine. C-protected cysteine was found to form a five-membered N,S-chelate ring (2). While imidazole coordination with N- and C-protected histidine could not be achieved, cationic pyrazolylborate-zinc-coligand complexes [TpZn-L]+ (4a, b) were obtained for L = 2-methylimidazole. The new complexes were characterized by their spectra and three structure determinations.

Notes: Organotungsten-selenolato complexes were prepared in moderate yields by insertion of selenium into the alkali metaltungsten bonds of MSeW(CO)3cp (M = Li, Na) and subsequent reactions with the organohalides o-, m-, and p- C6H4(CH2Br)2, C6H5CHBr2, m-C6H4(CHBr2)2 and C6H5CCl3. The 77Se-NMR data of the new complexes are discussed and compared with those of related complexes derived from organomonohalides. Moreover, the X-ray crystal structures of C6H5CH2W(CO)3cp (1), μ-[m-C6H4{CH2SeW(CO)3cp}2] (3), μ-[p-C6H4{CH2SeW(CO)3cp}2] (4), and C6H5CH[SeW-(CO)3cp]2 (5) were determined. In complex (1), the W-CH2 bond length is 2.374 Å; the W-Se bond lengths in the complexes 3, 4 and 5 are all in the range 2.625-2.655 Å, corresponding to W-Se single bonds.

Notes: The synthesis of a terphenyl derivative complexed by the cationic moiety Cp*Ru+ by Suzuki coupling of [Cp*Ru(BrC6H4Br)]OTf with phenyl boronic acid under catalysis of Pd(PPh3)4 in a DME-water mixture at 85°C in quantitative yield is reported. The stable coupling product 3 was characterized by X-ray crystal structure analysis.

Notes: Ruthenium complexes catalyze a variety of addition or isomerization reactions that are highly atom economical. Terminal alkynes react with allyl alcohols to form β,γ-unsaturated ketones that can be readily isomerized to α,β-unsaturated ketones via transient vinylidene complexes. A cyclization via a transient allenylidene complex concomitant with this addition represents a novel way to build heterocycles. Ancillary studies with these catalysts revealed an internal oxidation reduction whereby allyl alcohols are isomerized to saturated ketones and propargyl alcohols are isomerized to α,β-unsaturated carbonyl compounds. Consideration of the reaction mechanism led to a general Alder ene type reaction wherein alkynes serve as the enophile and alkenes serve as the ene component. These discoveries have led to a number of efficient total syntheses of biologically interesting targets. Mechanistic investigations into the activation of a ruthenium complex led to the discovery of a novel bis-homo-Diels-Alder reaction of 1,4-cyclooctadiene.

Notes: Stimulated by the recent detection of nitrosyl azide (N3—N=O), we investigated the stability of the sulfur analogues thionitriosyl azide (N3—N=S) and thiazyl azide (N3—S≡N) by using ab initio MO calculations up to the QCISD(T)/6-311+G(d)//QCISD/6-311G(d) + ZPE level. Both azides have a similar energy content. While thionitrosyl azide is not stable with respect to N2 elimination, thiazyl azide resists to this process by an energy barrier of about 110 kJ/mol. The NS and N3 fragments resulting from homolytic cleavage lie about 100 kJ/mol above the azides. The five-membered ring is thermodynamically much more stable than both azides but kinetically unstable with respect to cheletropic decomposition yielding N2S + N2. Overall, trans-thiazyl azide is the most likely candidate for experimental observation of, for example, the reaction of NS+ salts with the azide anion. IR wavenumbers of the azides were also predicted.

Notes: Syntheses, Properties, and Crystal Structures of the Titanium(III) Amido Complexes Ti[N(SiMe3)2]3, [TiCl2{N(SiMe3)2}(THF)2], and [Na(12-Crown-4)2][TiCl2{N(SiMe3)2}2]TiCl3(THF)3 reacts with NaN(SiMe3)2 to furnish [TiCl2{N(SiMe3)2}(THF)2] (1), whereas in the presence of 12-crown-4 the ionic amido complex [Na(12-crown-4)2][TiCl2{N(SiMe3)2}2] (5) is obtained besides [Na(12-crown-4)2][TiCl4(THF)] (4). On the other hand, the titanium(III) amido complex Ti[N(SiMe3)2]3 (2), the crystal structure of which was solved, reacts with NaN(SiMe3)2 in the presence of 12-crown-4 with deprotonation of one of the methyl groups to give the carbometalated complex [Na(12-crown-4)2][Ti{N(SiMe3)2}2{N(SiMe 3CH2)}] (3).

Notes: Leucascandrolide A ((+)-1), a doubly O-bridged 18-membered macrolide of a new type, i.e., showing little C1-branching vs. extensive 1,3-dioxygenation and a peculiar side chain, was isolated from a calcareous sponge of a new genus, Leucascandra caveolata BOROJEVIC and KLAUTAU from the Coral Sea. Transesterification of (+)-1 gave the methyl ester 3, derived from the side chain, and the 5-hydroxy derivative (+)-2, derived from the macrolide portion and with the natural configuration at C(5) (axial). Mosher's MTPA esters 4 and 5 obtained from (+)-2 showed scattered Δδ = (δ(S) - δ(R)) data. However, inversion of the configuration at C(5) led, via ketone (+)-6, to the less encumbered 5-equatorial hydroxy derivative (+)-7, whose MTPA esters 8 and 9 gave consistent Δδ data, allowing the assignment of the absolute configuration of (+)-7, and hence of (+)-1. The structural novelty of (+)-1 and its powerful antifungal and cytotoxic activities are likely to renew interest in calcareous sponges, previously limited to scarcely biologically active 2-aminoimidazoles.

Notes: Enantioselective Synthesis of α-PhosphinoketonesThe first asymmetric (C—P)-connective synthesis of α-phosphinoketones in high enantiomeric purity (e.e.91-97%) is described. Key step is the highly diastereoselective phosphinylation of SAMP-hydrazones (S)-2 to produce α-phosphinohydrazones (S,R)-3, isolated as the more stable borane adducts. Subsequent ozonolysis afforded the title compounds (R)-4, potential ligands for enantioselective homogeneous catalysis.

Notes: Ion/molecule reactions of ‘bare’ FeO+ with linear and branched aliphatic alcohols have been examined by Fourier-transform ion-cyclotron resonance mass spectrometry. Depending on the chain length of the alcohol, three different types of reactions can be distinguished: (i) Oxidation of the alcohols in the α-positions, to yield the corresponding carbonyl-Fe+ complexes, involves an initial O—H bond activation of the alcohol resulting in the formation of RO—Fe+—OH as the central intermediate. (ii) The formation of Fe(OH)2+, concomitant by loss of the corresponding neutral alkenes, competes with the generation of neutral OFeOH and a carbocation R+. These couples point to the existence of an intracomplex acid-base equilibrium and are connected with each other by a proton transfer from either acid to the other, e.g. i-C3H7+ + OFeOH⇄C3H6 + Fe(OH)2+. The process is driven by the Lewis acidity of FeO+ and starts with the abstraction of a hydroxide anion from the alcohol. (iii) For longer alcohols, e.g. pentanol, functionalization of non-activated C—H bonds which are remote from the O functionality is observed. Here, the OH group of the alcohol serves as an anchor, which directs the reactive metal-oxide cation toward a particular site of the hydrocarbon chain.

Notes: The population of the conformations obtained by rotation around the C(2)—N and the N—C(O) bonds of AllNAc, GlcNAc, and GlcNMeAc derivatives was investigated by 1H-NMR spectroscopy. The AllNAc-derived α-D-and β-D-pyranosides 4-7, the AllNAc diazirine 16, and the GlcNAc-derived axial anomers α-D-8-10 prefer the (Z)-anti-conformation. A significant population of the (Z)-syn-conformer in the (Z)-syn/(Z)-anti-equilibrium for the equatorial anomers β-D-8-10 and the GlcNAc diazirine 17 was evidenced by an upfield shift of H—C(2), downfield shifts of H—C(1) and H—C(3), and by NOE measurements. The population of the (Z)-syn-conformation depends on the substituent at C(1) and is highest for the hexafluoroisopropyl glycoside. The population of the (Z)-syn-conformation of β-D-14 decreases with increasing polarity of the solvent, but a substantial population is still observed for solutions in D2O. Whereas the α-D-anomers of the hemiacetal 22 and the methyl glycoside 21 prefer the (Z)-anti-conformation in D2O solution, the corresponding β-D-anomers are mixtures of the (Z)-anti-and (Z)-syn-conformers. The diazirine 17 self-associates in CD2Cl2 solution at concentrations above 0.005M at low temperatures. The axial anomers of the GlcNMeAc derivatives α-D-26-28 are 2:1 to 3:1 mixtures of (Z)-anti-and (E)-anti-conformers, whereas the corresponding β-D-glycosides are ca. 1:3:6 mixtures of (Z)-syn-, (Z)-anti-, and (E)-anti-conformers.

Notes: Reduction of a bis-radical precursor, 6-phenyl-1,1-bis[3-(phenylselanyl)propyl]-3a,4-dihydro-1H,3H-cyclopenta[c]furan-5-one (6), with 3 equiv. of Ph3SnH provides mixtures of cis,cis- or cis,trans-angular triquinane products (3aα,5aβ,8β,8aR*)- and (3aα,5aα,8β,8aR*)-hexahydro-3a-propyl-8-phenyl-5H-dicyclopenta[b,c]furan-7(8H)-one (cis,cis-12/cis,trans-12), in yields that vary from 50%/50% to 91%/6% depending on the reaction concentration. A mechanistic model for this process is proposed that involves a non-selective phenylselenium-group abstraction step followed by successive kinetic resolutions of diastereoisomeric radical intermediates. This reaction shows how yields in group-selective reactions can be compounded to levels above that ostensibly permitted by the level of the group-selective step.

Notes: Acid-catalyzed cyclic ketal formation vs. hydrolysis of a series of hydroxyalkyl cyclic enol ethers in the presence of 1 equiv. of H2O, and acid-catalyzed cyclic-ketal formation (same ketals as above) vs. methanolysis of a series of mixed pent-4-enyl hydroxyalkyl ketals with N-bromosuccinimide in the presence of 4 equiv. of MeOH led to the same result: the intramolecular cyclization processes occur at similar rates as the intermolecular H2O or MeOH attacks independently of the size of the rings formed (five-, six-, or seven-membered), by cyclizations. These results can be explained by the facts that, due to stereoelectronic effects which impose a torsional strain to the sp2 hybridized O-atom, the cyclization activation enthalpy decreases, as the length of the hydroxyalkyl chain increase (ease of cyclization: 7 〉 6 〉 5), whereas the entropy factor favors the cyclization in the reverse fashion (ease of cyclization: 5 〉 6 〉 7). The various reaction pathways have been examined using the semi-empirical Hamiltonian AM1, and the results obtained confirm that large-ring formation is enthalpically much favored over the cyclization processes leading to small rings (ease of cyclization: 7 〉 6 〉 5).

Notes: The reduction of pyrene with sodium in aprotic diethyl ether allows to crystallize the extremely air-sensitive radical ion pair pyrene-sodium-diethylether. The single-crystal structure determination at 130 K shows that each sodium counter cation, solvated by one diethyl-ether molecule, is η3- and η6-coordinated to one of the short-axis six-membered rings of two pyrene radical anions. The resulting dibenzene-sodium sandwiches form a string, in which the hydrocarbon planes are canted to each other by 62°. In the pyrene radical-anion skeleton, no distortion due to its negative charge can be detected relative to that of the neutral molecule. From the temperature-dependent signal multiplets of preceding ESR investigations, the solvent-separated pyrene radical anion as well as two different contact radical-ion pairs had been identified and their structures in solution approximated by potential-energy estimates. Referring to the recently discovered long-axis Na⊕ contact ion pair polymorph, crystallized at lower temperatures, the structure reported here represents the second and probably thermodynamically more stable one. Both the ESR and the structural results provide some insight into the multidimensional networks of equilibria in aprotic solution, which are activated by alkali-metal reduction of unsaturated organic compounds.

Notes: The electrochemical transfer of quinidine across the H2O/1,2-dichloroethane interface was investigated by cyclic voltammetry, so as to determine its lipophilicity. The formal transfer potential was measured as a function of the pH of the aqueous phase. Both singly and doubly protonated quinidine cations can transfer across the interface, and their formal Gibbs free energies of transfer were observed to be 7.7 and 31.2 kJ mol-1, respectively. Between pH 0 and 3, only the doubly charged quinidine was present in the aqueous phase and was observed to transfer. Between pH 3 and 6, the transfer of both cations occurred. The proportion of doubly charged quinidine decreased progressively in this pH range and disappeared completely above pH 6. The overall process was analyzed using a thermodynamic model. The relationship between the various forms of quinidine in both phases and pH was established and found to be in good agreement with the experimental results. With this model, the acid-base equilibrium constants in the organic phase could be calculated as pKa1o = 9.66 ± 0.21 and pKa2o = 14.20 ± 0.16 (the subscripts a1o and a2o refer to the first and second dissociation constants). This study illustrates how the partition of ionic species can be taken into account in the determination of lipophilicity and in the description of the passive transfer of organic drugs.

Notes: A chiral center in a drug molecule increases the complexity of synthetic, metabolic, pharmacological, and clinical studies, an additional problem being a possible lack of configurational stability. Here, we report detailed kinetic and mechanistic studies on the deuteration and racemization of seven 5-monosubstituted hydantions (= imidazolidine-2,4-diones) used as model compounds. Using 1H-NMR and chiral RP-HPLC, rates of reaction and thermodynamic parameters of activation were determined for the reactions of deuteration and racemization. Energies of deprotonation were obtained by molecular-orbital calculations performed at the AM1 level. It is demonstrated that the deuteration and racemization of 5-monosubstituted hydantoins follow general-base catalysis. The identical (within experimental errors) activation energies of deuteration and racemization indicate that the two reactions share a common reaction mechanism. The fact that the pseudo-first-order rate constants of deuteration are about half of those of racemization suggests that deuteration occurs with inversion of configuration. Very large differences in reaction rates were observed between the seven compounds, indicating the marked influence of substituents on chiral stability. These results, together with the small isotope effects observed, and the comparison between experimental activation energies and calculated energies of deprotonation, suggest a SE2 push-pull mechanism for the racemization of 5-monosubstituted hydantoins.

Notes: Crystal and solution structures of the [PdII(η3-allyl)] and of the [PdII(η3-1,3-diphenylallyl)] complexes, 4 and 5, respectively, with (4S)-4-benzyl-2-[2′-(diphenylphosphino)phenyl]-4,5-dihydrooxazole (3) were determined by X-ray crystallography and 2D-NMR spectroscopy. Complex 4 proved to be disordered with both diastereoisomeric complexes in the crystal. The results of X-ray and NMR experiments demonstrate a good agreement between solution and solid-state equilibria of the two isomers. A comparison with dichloro{(4S)-2-[2′-(diphenylphosphino)phenyl]-4,5-dihydro-4-phenyloxazole-P,N}zinc(II) (2b) shows a surprising conformational stability of the coordinated phosphinooxazole ligand 3.

Notes: 1,5-Dipolar Electrocyclization of Acyl-Substituted ‘Thiocarbonyl-ylides’ to 1,3-OxathiolesThe reaction of α-diazoketones 15a, b with 4,4-disubstituted 1,3-thiazole-5(4H)-thiones 6 (Scheme 3), adamantanethione (17), 2,2,4,4-tetramethyl-3-thioxocyclobutanone (19; Scheme 4), and thiobenzophenone (22; Scheme 5), respectively, at 50-90° gave the corresponding 1,3-oxathiole derivatives as the sole products in high yields. This reaction opens a convenient access to this type of five-membered heterocycles. The structures of three of the products, namely 16c, 16f, and 20b, were established by X-ray crystallography. The key-step of the proposed reaction mechanism is a 1,5-dipolar electrocyclization of an acyl-substituted ‘thiocarbonyl-ylide’ (cf. Scheme 6). The analogous reaction of 15a, b with 9H-xanthen-9-thione (24a) and 9H-thioxanthen-9-thione (24b) yielded α,β-unsaturated ketones of type 25 (Scheme 5). The structures of 25a and 25c were also established by X-ray crystallography. The formation of 25 proceeds via a 1,3-dipolar electrocyclization to a thiirane intermediate (Scheme 6) and desulfurization. From the reaction of 15a with 24b in THF at 50°, the intermediate 26 (Scheme 5) was isolated. In the crude mixtures of the reactions of 15a with 17 and 19, a minor product containing a CHO group was observed by IR and NMR spectroscopy. In the case of 19, this side product could be isolated and was characterized by X-ray crystallography to be 21 (Scheme 4). It was shown that 21 is formed - in relatively low yield - from 20a. Formally, the transformation is an oxidative cleavage of the C=C bond, but the reaction mechanism is still not known.

Notes: The bicyclic and tricyclic meso-N-(methylsulfonyl)dicarboximides 1a-f are converted enantioselectively to isopropyl [(sulfonamido)carbonyl]-carboxylates 2a-f by diisopropoxytitanium TADDOLate (75-92% yield; see Scheme 3). The enantiomer ratios of the products are between 86:14 and 97:3, and recrystallization from CH2Cl2/hexane leads to enantiomerically pure sulfonamido esters 2 (Scheme 3). The enantioselectivity shows a linear relationship with the enantiomer excess of the TADDOL employed (Fig.3). Reduction of the ester and carboxamide groups (LiAlH4) and additional reductive cleavage of the sulfonamido group (Red-Al) in the products 2 of imide-ring opening gives hydroxy-sulfonamides 3 and amino alcohols 4, respectively (Scheme 4). The absolute configuration of the sulfonamido esters 2 is determined by chemical correlation (with 2a,b; Scheme 6), by the X-ray analysis of the camphanate of 3e (Fig. 1), and by comparative 19F-NMR analysis of the Mosher esters of the hydroxy-sulfonamides 3 (Table 1). A general proposal for the assignment of the absolute configuration of primary alcohols and amines of Formula HXCH2CHR1R2, X = O, NH, is suggested (see 11 in Table 1). It follows from the assignment of configuration of 2 that the Re carbonyl group of the original imide 1 is converted to an isopropyl ester group. This result is compatible with a rule previously put forward for the stereochemical course of reactions involving titanium TADDOLate activated chelating electrophiles (12 in Scheme 7). A tentative mechanistic model is proposed (13 and 14 in Scheme 7).

Notes: The novel H2O-soluble cyclophanes 1 and 2 incorporating different anion-recognition sites were prepared in short synthetic routes (Schemes 1 and 2) as first-generation mimics of the natural, D-Ala-D-Ala binding antibiotic vancomycin. The X-ray crystal structure of 1, a tris(hydrochloride)salt, revealed an open, preorganized cavity of sufficient size for the incorporation of small aliphatic residues (Fig. 3). In the crystal, molecules of 1 are arranged in parallel stacks, generating two types of channels, an ‘intra-stack’ channel passing through the cyclophane cavities and an ‘inter-stack’ channel located between cyclophane stacks (Fig. 4). The strongest intermolecular interactions between macrocycles in the crystal are C=O…H—N H-bonds between the carboxamide residues of adjacent cyclophanes in neighboring stacks (Fig. 5). The ‘intra-’ and ‘inter-stack’ channels incorporate the three ordered Cl- counterions and several, partially ordered solvent molecules (4 MeOH, 1 H2O) (Fig. 6). Counterion Cl(2) is located within the ‘intra-stack’ channel and interacts with a protonated piperazinium N-atom and both ‘intra-stack’ MeOH molecules. The two other counterions, Cl(1) and Cl(3), are located within the ‘inter-stack’ channel. They are connected to two MeOH and one H2O molecules and also interact both with the NH2+ group of the protonated spiropiperidinium ring in 1, forming an infinite, chain-like H-bonding network …Cl(1)…HOH…MeOH…Cl(3)…HNH…Cl(1′)…. Both ‘intra-’ and ‘inter-stack’ MeOH molecules undergo weak CH…π interactions with neighboring aromatic rings. Cyclophane 1 complexed aromatic sulfonates in 0.5M KCl/DCl buffer in D2O, whereas the tetrakis(quaternary ammonium) receptor 2 bound the sodium salts of aliphatic and aromatic carboxylates and sulfonates, of N-acylated α-amino acids as well as of N-acetyl-D-alanyl-D-alanine (Ac-D-Ala-D-Ala), a substrate of vancomycin, in pure H2O. In all of these complexes, ion pairing between the cationic recognition site in the periphery of the cyclophane receptor and the anionic substrates represents the major driving force for host-guest association. The 1H-NMR analysis of complexation-induced changes in chemical shift clearly demonstrated that, in solution, this ion pairing exclusively takes place outside the cavity. Nevertheless, the macrocyclic bridges are essential for the efficiency of the anion-recognition sites in the two cyclophane receptors 1 and 2. Control compounds 3 and 4 possess nearly the same anion-recognition sites than 1 and 2, but lack their macrocyclic preorganization; as a consequence, they do not form stable ion-pairing complexes with mono-anionic substrates in the considered concentration ranges ( 〈 50 mM) in D2O.

Notes: 2′-Deoxy-5-(isothiazol-5-yl)uridine (12) was synthesized starting from 2′-deoxy-5-iodouridine using a Pd-catalysed cross-coupling reaction with propiolaldehyde diethyl acetal followed by deprotection and ring closure using thiosulfate. 2′-Deoxyuridine 12 has a particular place among the 5-heteroaryl-substituted 2′-deoxyuridines in that it has a high affinity for herpes simplex virus type 1 (HSV-1)-encoded thymidine kinase (TK) without antiviral activity. Biochemical studies revealed that 12 is a substrate for viral TK. We further investigated the interaction of 12 with the HSV-1 thymidine kinase. The conformation of 12 in solution was established by NMR spectroscopy. The most stable conformer 12A has the S-atom of the isothiazole ring placed in the neighbourhood of the C(4)=O group of the pyrimidine moiety. The compound was docked in its most stable conformation in the active site of HSV-1 TK and subjected to energy minimization. This demonstrated that the isothiazole moiety binds in a cavity lined by the side chains of Tyr-132, Arg-163, Ala-167, and Ala-168 and that the C(3) atom of the isothiazole moiety is located in close proximity of the phenolic O-atom of Tyr-132 and the aliphatic part of the Arg-163 side chain.

Notes: The synthesis of C-glycosidic analogues 15-22 of N4-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-L-asparagine (Asn(N4GlcNAc)) possessing a reversed amide bond as an isosteric replacement of the N-glycosidic linkage is presented. The peptide cyclo(-D-Pro-Phe-Ala-CGaa-Phe-Phe-) (CGaa = C-glycosylated amino acid; 24) was prepared to demonstrate that 3-[(3-acetamido-2,6-anhydro-4,5,7-tri-O-benzyl-3-deoxy-β-D-glycero-D-guloheptonoyl)amino]-2-[(9H-fluoren-9-yloxycarbonyl)amino]propanoic acid (22) can be used in solid-phase peptide synthesis. The conformation of 24 was determined by NMR and molecular-dynamics (MD) techniques. Evidence is provided that the CGaa side chain interacts with the peptide backbone. The different C-glycosylated amino acids 15-21 were prepared by coupling 3-acetamido-2,6-anhydro-4,5,7-tri-O-benzyl-3-deoxy-β-D-glycero-D-gulo-heptonic acid (4) with diamino-acid derivatives 8-14 in 83-96% yield. The synthesis of 4 was performed from 2-(acetamido-3,4,6-tri-O-benzyl-2-deoxy-β-D-glucopyranosyl) tributylstannane (2) by treatment with BuLi and CO2 in 83% yield. Similarly, propyl isocyanat yielded the glycoheptonamide 7 in 52% from 2. Compound 2 was obtained from 2-acetamido-3,4,6-tri-O-benzyl-2-deoxy-D-glucopyranose (1) by chlorination and addition of tributyltinlithium in 74% yield. A procedure for a multigram-scale synthesis of 1 is given.

Notes: Steroselective Synthesis of the Nitrite-Reducing Cofactor Heme d1 from HematoporphyrinThe nitrite-reducing cofactor heme d1 has been synthesized in a few synthetic steps, starting from readily accessible hematoporphrin dimethyl ester (rac-4a). A single-crystal structure analysis of the synthesized target molecule rac-10a unequivocally established the constitution and the relative configuration of heme d1 (3).

Notes: Glycosylrifamycins, a new type of semisynthetic rifamycin derivatives, can be easily obtained by reaction of 3-(2-aminoethylthio)rifamycin SV (2) with a glycosyl compound carrying a coupling group, such as isothicyanate or carboxy. We prepared O-acetylated and free glucopyranosyl and arabinopyranosyl derivatives of rifamycin S and SV (see 3-10). Additionally, derivatives with D-saccharo-1,4-lactone and with shikimic acid were obtained (see 11-15). Glycosylrifamycins show an interesting inhibitory power on Gram-positive bacteria (Table).

Notes: Azapropazone (1) is a non-steroidal anti-inflammatory drug (NSAID) whose chemical structure is markedly different from that of other agents in this class and challenges our understanding of structure-activity and structure-permeation relationships. Using a variety of experimental and computational techniques, we studied 1 for its molecular structure in the gas phase and non-protic polar solvents, protonation/deprotonation equilibra, tautomerism, and pH-lipophilicity profiles (octan-1-ol/H2O and dodecane/H2O). Other NSAIDs and model compounds were also examined for comparison. Due to its very low acidic pKa1, 1 exists in the physiological pH range as a zwitterion and as an anion. Some pharmacological implications of these findings are discussed.

Notes: As a continuation of our previous studies on the synthesis and antiplatelet activity of coumarin derivatives of α-methylidene-γ-butyrolactones, certain quinoline, flavone, and xanthone derivatives were synthesized and evaluated for antiplatelet activity against thrombin (Thr)-, arachidonic acid (AA)-, collagen (Col)-, and platelet-activating factor (PAF)-induced aggregation in washed rabbit platelets. These compounds were synthesized from quinolin-8-ol, flavon-7-ol, and xanthon-3-ol, respectively, via alkylation and Reformatsky-type condensation (Schemes 1-3). By the comparison with comparison with coumarin α-methylidene-γ-butyrolactone 3a, flavone and xanthone derivatives, 3b and 3c, respectively, are more selective in which only AA- and collagen-induced aggregation are strongly inhibited. Most of the quinoline derivatives (9a-e) exhibited broad-spectrum antiplatelet activities.

Notes: Facilitated proton transfer may be of potential significance in pharmacokinetic and pharmacodynamic processes. Here, we show that the NSAID piroxicam and its N-and O-methylated derivatives act as ionophores for proton transfer across the H2O/1,2-dichloroethane interface. Investigations by cyclic voltammetry showed that the proton transfer occurs by interfacial protonation of the ionophore. The dissociation constants of the three compounds in the organic phase were calculated by Matsuda's theory. With this particular transfer mechanism, the present study exemplifies how electrochemistry at a liquid/liquid interface can be applied to calculate the fundamental thermodynamic parameters related to the pharmacokinetic behavior of ionic drugs.

Notes: The chiral N-(2-benzoylethyl)-N-tosylglycine esters 5a-h and the α-amino-γ-keto ester 6 were prepared from γ-(tosylamino) alcohols 7a-h. Irradiation of compounds 5a-c, e gave cis-3-hydroxyproline esters 20-23 (Scheme 6), partly with complete asymmetric induction by the C(1′)-substituent, whereas 6 gave enantiomerically pure 4-hydroxy-4-phenyl-L-proline esters 24 in good yield but low de (Scheme 6). The de of the photocyclization depended on the nature and/or size of the C(1′)-substituents. Irradiation of ketones 5d and 5f, bearing H-atoms at C(γ) with respect to the keto function, gave cyclobutanols (Scheme 9) in low yields besides the preferred Norrish-type-II cleavage product. Cyclopentanol 25 was a by-product of the photocyclization of 5c as a result of H—C(δ) abstraction from the t-Bu group. The structure of products 20, 22, and 24a, b was established by NMR or X-ray analyses.

Notes: Optically Active 3-Amino-2H-azirines as Synthons for Enantiomerically Pure αα-Disubstiuted α-Amino Acids: Syntheses of Isovaline Synthons and a Segment of Trichotoxin A-50The synthesis of a novel 3-amino-2-methyl-2-[2-(phenylsulfonyl)ethyl]-2H-azirine derivative 12 with a chiral substituent at the amino group is described. Chromatographic separation of the diastereoisomer mixture gave pure diastereoisomers which, after an electrochemical cleavage of the phenylsulfonyl group, yielded the (S)- and (R)-isovalin (Iva) synthons 13a and 13b, respectively. The absolute configuration of the precursor molecule 12b was established by X-ray crystallography. The Iva synthons were successfully used in the synthesis of the C-terminal pentapeptide Z-Leu-Aib-(R)-Iva-Gln-Valol of the peptaibole Trichotoxin A-50 and its epimer.

Notes: A series of new chiral diselenides with a N-atom in the side chain was prepared by a short synthetic sequence (Scheme 1). Only 1 mol-% of these diselenides catalyzed very effectively the diethylzinc addition to various aromatic and α,β-unsaturated aldehydes yielding the secondary alcohols in up to 98% ee (Scheme 2 and Tables 1 and 2). An asymmetric amplification was observed with these catalysts. Detailed NMR studies were performed to characterize the catalytically active species.

Notes: An asymmetric synthesis of the spermidine alkaloid (-)-(2R)-dihydromyricoidine (5) was performed by employing two ring-enlargement reactions. The chiral center was introduced by a diastereoselective Michael addition of perhydropyridazine (7) to the α,β-unsaturated ester 6. The (Z)-C=C bond was obtained by a selective Wittig reaction. The synthetic compound 5 was found to have a negative value for the specific rotation. This is in contrast to that of the natural product reported in the literature. Therefore, as an outcome of this synthesis, the absolute configuration of the natural alkaloid should be inverted to be as shown in structure V.

Notes: A novel preparation of methyl (13S)-13-hydroxyisoatisiren-18-oate (4), a key-intermediate in a synthesis of (+)-methyl trachyloban-18-oate ((+)-1), from (-)-abietic acid, is described. Since (-)-1 has been previously converted into (-)-methyl 16-oxo-17-norkauran-18-oate ((-)-16), our preparation of 4 constitutes also a formal total synthesis, from (-)-abietic acid, of (+)-16. Key steps in this approach were the allene photoaddition to podocarp-8(14)-en-13-one (5) and the conversion of the endo-toluene-4-sulfonate 11 into the exo-benzoate 12b.

Notes: 6-Aminopyrazin-2(1H)-one, when incorporated as a pyrimidine-base analog into an oligonucleotide chain, presents a H-bond acceptor-donor-donor pattern to a complementary purine analog. When paired with the corresponding donor-acceptor-acceptor purine in oligonucleotides, the heterocycle selectively contributes to the stability of the duplex, presumably by forming a base pair of Watson-Crick geometry joined by a non-standard H-bonding pattern. Aspects of the nucleoside chemistry, including syntheses of the β-furanosyl ribonucleoside 1, the ribonucleoside triphosphate 2 and the ribonucleoside bisphosphate 3 of 6-aminopyrazin-2(1H)-one are reported here. In aqueous solution, the ribonucleoside 1 was found to undergo acid- and base-catalyzed rearrangement with an apparent half-life of ca. 63 h at neutral pH and 30°. The rearrangement appears to be specific acid- and base-catalyzed. The thermodynamically most stable compound formed during this rearrangement reaction was isolated by HPLC and shown to be the β-pyranosyl form 4 of the 6-aminopyrazin-2(1H)-one nucleoside in its 4C1 chair conformation. This reactivity of 1 under physiological conditions may explain why Nature does not use this particular heterocyclic system to implement an acceptor-donor-donor H-bonding pattern in the genetic alphabet.

Notes: The crystal structure of a glycopeptide antibiotic A-40926 aglycone was investigated by X-ray analysis at -120°. A-40926 crystallises in the orthorhombic space group P212121 with two monomers in the asymmetric unit, a = 21.774(4), b = 28.603(7), c = 29.757(4) Å. ‘Conventional’ direct methods approach failed to solve the structure, but a novel iterative real/reciprocal space procedure was successful. Refinement against 11248 F2 data led to R1 = 13.3% for 6770 F 〉 4σ (F). The two monomers of A-40926 have similar conformations and are bound by antiparallel H-bonds to form a ‘chain’ structure of connecting dimers. The antibiotic molecule possesses a ‘binding pocket’ for the C-terminal carboxy group of the cell-wall protein, which is consisten with suggestions based on NMR data and the recently reported crystal structure of ureido-balhimycin. In A-40926 the monomers are polymerically linked by H-bonds, quite unlike the tight dimer formation observed in ureido-balhimycin.

Notes: The radical anions and the radical cations of dipleiadiene (dicyclohepta[de,ij]naphthalene; 1) and its 12b, 12c-homo derivative 2 were characterized by ESR and ENDOR spectroscopy. Their singly occupied orbitals are related to the degenerate nonbonding MOs of a 16-membered π-perimeter. The π-spin distribution over the perimeter is similar in the radical cations 1.+ and 2.+, and an analogous statement holds for the radical anions 1.- and 2.-. However, deviations of the π-system from planarity lead to a decrease in the absolute values of the negative coupling constants of the perimeter protons in 2.+ and 2.- relative to those in 1.+ and 1.-. The hyperfine data for the perimeter protons in the radical ions correlate with the changes in 13C chemical shifts on passing from the neutral compounds to the corresponding diions. It is concluded from the coupling constants of the CH2 protons in the radical ions of 2 that the cation 2.+ exists in the methano-bridged form (A) of the neutral 2 (and, presumably, also of the dication 22+), whereas the anion 2.- adopts the bisnorcaradiene form (B) of the dianion 22-.

Notes: The synthesis of the linear tris[terpyridine] 1 with three tridentate binding sites is described. The reaction with metal ions of octahedral coordination geometry, such as FeII or NiII, leads to the self-assembly of trinuclear complexes [M3(1)2]6+, which display properties in agreement with a double helical structure. The trinuclear iron (II) helicate has been resolved into its enantiomers.

Notes: The crystal structure of isocyclosporin A (1), a rearrangement product of the immunosuppressant drug cyclosporin A, has been determined at 193 (2) K. Crystals are orthorhombic with cell dimensions a = 26.684 (7), b = 26.936 (3) Å, c = 28.549 (7) Å, space group C2221. The structure was solved by direct methods and refined by full-matrix least-squares methods to a conventional R value of 0.110. In contrast to the structure of cyclosprin A in solution and in the crystal, isocyclosporin A (1) has no regular secondary structural elements. The backbone adopts an open, irregular conformation with cis amide bonds between residue 2 and 3, and 3 and 4, respectively. All the other amide bonds and the ester linkage are trans. Contrary to crystal structures of cyclosporin derivatives, this crystal structure is stabilized by two transannular and four intermolecular H-bonds.

Notes: A practical synthesis of both enantiomers of 2-(tert-butyl)-2-methyl-1,3-dioxolan-4-one starting from D-mannitol is reported. These compounds are chiral equivalents of glycolic acid (= hydroxyacetic acid) which are configurationally stable and can be alkylated via their enolates.

Notes: Formation constants of ternary complexes of CuII with (S)-amino-acid amides ((S)-phenylalaninamide, (S)-prolinamide, and (S)-tryptophanamide) and (R)- or (S)-histidine and (R)- or (S)-tyrosine were determined potentiometrically in aqueous solution. Significant stereoselectivity was presented by all three amides towards histidine, the diastereoisomeric complexes with ‘heterochiral’ ligands being more stable than those with ‘homochiral’ ligands (see Table 3). The stereoselectivity observed with (S)-phenylalaninamide and (S)-tryptophanamide may be explained on the basis of hydrophobic stacking interactions between 1H-imidazole and the aromatic side chain, favoured by the terdentate behaviour of histidine (see Fig.2), whereas repulsive effects seem to be prevalent with (S)-prolinamide. Only (S)-prolinamide and (S)-phenylalaninamide show appreciable stereoselectivity with tyrosine, which is bidentate, probably on account of repulsive interactions. The present results on the stability of ternary complexes in solution allow to draw some conclusions on the mechanism of chiral discrimination performed by CuII complexes of (S)-amino-acid amides added to the mobile phase in HPLC (reversed phase).

Notes: Complexes of Halide Ions with Diiodoacetylene. The Crystal Structures of PPh4[X(I-C≡C-I)2] with X = Cl, Br, IThe complexes PPh4[X(I-C≡C-I)2] with X = Cl (1), Br (2), and I (3) have been prepared from the phosphonium salts PPh4X and 1-C≡C-I in dichloromethane solutions. 1-3 form colourless crystals, which according to crystal structure analysis crystallize isotypically in the space group P421m with two formula units per unit cell. The diiodacetylenes are coordinated by the halide ions X- in a distorted tetragonal fashion, the I-C≡C-I molecules being in μ2-bridging function. Thus, a polymeric anionic network [X(I-C≡C-I)2]nn- with a layered structure results.

Notes: The synthesis and coordination chemistry of 2-(2-pyridyl)-phosphinines and 2,2′-biphosphinines are reviewed. A noteworthy series of homoleptic complexes of 4,4′,5,5′-tetramethyl-2,2′-biphosphinine (tmbp) with Cr(0), Mo(0), Wo(0) and Ni(0) are described. A [Cu(bpy)(tmbp)]+ cationic polymer has been characterized by X-ray analysis. Ruthenium, manganese and rhenium chelates were also obtained. With Mn2(CO)10, a (tmbp)-Mn2(CO)6 complex is formed where tmbp acts as an eight electron donor.

Notes: The reaction of InBr/InBr3 or InBr/BrIn[(CH2)3NMe2]2 with the transition metal dimers [L(CO)nM]2 {L = CO, Cp, C5H4[(CH2)2NMe2]; M = Fe, Co, Ni; n = 1-3} in THF or dioxane gives in almost quantitative yield the transition metal indium complexes L(CO)nM—InBr2(Do) (Do = THF, NC7H13) and L(CO)nM—In[(CH2)3NMe2](Br) respectively. The new compounds were characterized by elemental analysis, infrared v(CO) spectroscopy, NMR, and mass spectrometry. An X-ray single crystal structure determination of (η5-C5H5)(CO)-Ni-InBr2(NC7H13) (1a) revealed a short Ni-In bond of 246.3(1) pm.

Notes: An improved synthesis of [(2-phosphanylethyl)cyclopenta-dienyl]cobalt(I) chelate complexes is presented, in which the paramagnetic chloride 3 is a precursor of the ethene complex 4. The latter readily undergoes ligand exchange reactions which in the case of bidendate reagents (1,5-cyclooctadiene, 1,2-bis(diisopropylphosphanyl)ethane, 2,2′-bipyridine, nor-bornadiene) cause a decomplexation of the phosphane arm at room temperature with formation of 7, 5, 6, 8. The ethene ligand in 4 can be replaced by alkynes under equally mild reaction conditions (formation of 9, 11 - 16). The reaction with ethyne results in the formation of vinylidene complex 10. The yields of the reactions with nonaromatic alkynes could be improved by treating 3 with the alkyne in the presence of sodium amalgam. The unsubstituted vinylidene complex 10 and its tert-butyl derivative 17 were obtained by this route in 38 and 40% yield, respectively.

Notes: Cesium-Fluorine Four-Membered Rings as Structural Motive in Cesium Triorganofluoro Metalates of Group 13The reactions of AlMe3, GaMe3, and InMe3 with CsF in acetonitrile furnish the corresponding trimethylfluoro metalates Cs[Me3MF] (1: M = Al, 2: M = Ga, 3: M = In). The salt-like compounds 1 - 3 were characterized by NMR, IR, and MS techniques as well as by X-ray structure analysis. Cs2F2 four-membered rings are the structure-dominating units in all three compounds. Compound 1 consists of puckered layers of weakly associated Cs2F2 rings parallel to (100), while the four-membered rings in 2 form infinite ladder-type chains. The Cs-F rings in 3 build up a heterocubane with a Cs4F4 core by ring stacking.

Notes: The crystal structures obtained by X-ray methods of (tert- butoxy)alane and -gallane (tBuOMH2) are isotypic and are composed of discrete centrosymmetric dimers. The dimers arise from almost symmetrical Al—O—Al [1.810(3), 1.815(3) Å] and Ga—O—Ga [1.902(9), 1.908(9) Å] bridges forming a central rhombohedral four membered M2O2 cycle [O—Al—O 81.0(2)°, O—Ga—O 78.6(5)°] with the metallic atoms in a distorted tetrahedral environment. When one of the hydride ligands on the metals is further substituted by tert-butoxy, the formation of (tBuO)2AlH and (tBuO)2 GaH is observed. These two compounds crystallize in different lattices and space groups, but they are nevertheless very similar in their structure: the centrosymmetric M2O2 cycle is maintained [Al—O 1.817(3), 1.817(3) Å; Ga—O 1.904(4), 1.907(4) Å] As expected, the terminal Al-O [1.675(3) Å] and Ga—O [1.783(4) Å] distances are considerably shorter than the bridging ones.

Notes: Treatment of hexa-tert-butylcyclotrigermane (3) with CCl4, Br2, and I2 furnishes the correspondingly substituted 1,3-dichloro- (4), 1,3-dibromo- (5), and 1,3-diiodotrigermanes (6). The symmetries of the molecules of 5 and 6 are very similar (point group C1) revealing gauche-anti conformations and different Ge—Ge bond lengths. However, while 5 crystallizes as a racemate, 6 forms a conglomerate of enantiomerically pure crystals. The X-ray structure analysis of the 1,3-dimethyltrigermane (7) derivative, derived from 6 by a sequence of metalation and methylation reactions, reveals more symmetrical molecules of the point group C2 which also crystallize as a racemate. Irradiation of 3 leads to tetra-tert-butyldigermene (8) and di-tert-butylgermylene (9) which could be trapped by addition and cycloaddition reactions with selenium, tellurium, and 3,5-di-tert-butyl-1,2-benzoquinone.

Notes: The cationic ferracyclic carbene complexes 1 react with carbon nucleophiles like lithium enolates and organocuprates to give the corresponding 4-substituted 1, (3E)-diene tricarbonyl-iron complexes 6 and 9. The reaction is thought to proceed by initial attack on the allyl terminus and subsequent ferra Claisen-Ireland rearrangement of the intermediate (η2 alkene)carbene complex 4. This rationale is supported by the isolation and characterisation of analogous aminooxocarbene derivatives 8. With sterically demanding enolates products 6 are formed in diastereomeric ratios of up to 90:10, thus demonstrating the inductive power of the chiral metallacycle in 1. Lithium acetylides as carbon nucleophiles react with 1 according to a novel cascade to give regio- and stereospecifically 2,5,5-trisubstituted-cyclopentenones 10 suggesting a concerted formation of four C=C bonds together with a CO insertion and a formal carbene transfer step.

Notes: The zinc complex chemistry of the tridentate thiol ligand N- (2-mercaptophenyl)(2-picolyl)amine (MPPAH) differs considerably from that of the aliphatic analogue N-(2-mercaptoethyl)(2-picolyl)amine reported previously. This is due to the lower basicity and hence bridging tendency of its aromatic thiolate function. With zinc salts of oxo anions the 1:1 complexes (MPPA)ZnX (1a-c: X = ONO2, OAc, OBz) are formed which according to spectroscopic data are monomeric while the halide (MPPA)ZnBr (2) seems to be polymeric. In the absence of coordinating anions the monomeric 2:1 complex (MPPA)2Zn (3) results which according to a crystal structure determination contains tetrahedral zinc coordinated by one MPPA ligand in a tridentate fashion while the other is only monodentate and sulfur-bound. A similar N2S2 coordination can be deduced for the 1:1:1 complex (MPPA)Zn(STrt) (4) resulting from ZnEt2, MPPAH and triphenylmethanethiol.

Notes: Reaction of bis(diisopropylamino)phosphenium triflate (1[CF3SO3]) with silver salts AgY [Y- = CF3CO2- (2a), CF3-SO3- (2b), CH3CO2- (2c)] affords neutral complexes [{(iPr2N)2(Y)P} Ag(OSO2CF3)] (3a-c). While 3a, c are stable up to ambient temperature, 3b is only stable at low temperature and in equilibrium with the cation 1. The constitution of 3a-c was derived from multinuclear (1H, 13C, 31P, 109Ag) NMR spectra. Compound 3a was further studied by X-ray single-crystal diff ractommetry which showed the presence of dimeric units with μ2-bridging triflate ligands and three-coordinate silver atoms with a planar T-shaped coordination geometry. Reaction of 4-chloro-1,3-bis(2,6-dimethylphenyl)-1,3,2-diazaphospholenium triflate (4[CF3SO3]) with 2a, c affords equilibrium mixtures whose 31P- and 109Ag-NMR spectra suggested the presence of silver complexes 5a, c with constitutions similar to those of 3a, c besides unreacted cation 4. No reaction was observed between 4[CF3SO3] and 2b. A common mechanism accounting for the different outcome of the individual reactions will be discussed.

Notes: The reaction of 2,5-dihydro-4,5,5-trimethyl-2,2-di-2-pyridyl-imidazole-1-oxyl (L) with AgSbF6 gives the complex [Ag2L2]2+[SbF6-]2 which was characterized by X-ray diffraction. - The complex (a biradical) forms a four-membered ring with two Ag(I) ions and two imine nitrogen atoms of the imidazolines with a relatively short Ag - Ag distance [2.839(2) Å]. Magnetic measurements indicate that two nitroxide radicals are slightly coupled.

Notes: The crown thioether 3 with the novel diisopropylidene building block was synthesized by an S′N cyclization reaction of 2,7-dichloro-2,7-dimethylocta-3,5-diyne (1) with 3-thia-pentane-1,5-dithiol (2). Ligand 3 shows all the sulfur centers in exodentate positions. Reaction of 3 with Ag1 triflate and triphenylphosphane yielded the tetrahedral complex 4, which shows unique spectroscopic data in solution. Crystallization furnished two different crystal forms (4a and 4b). Both are different conformers which are stable in the solid state. 4a exhibits a crown-like structure of the thioether ligand with cisoid S—C—C—S chains. To our knowledge 4b is the first silver(1) complex with a crown thioether retaining the tran-soid S—C—C—S conformation in the metal complex.

Notes: Cationic metallacyclic carbene complexes of iron and cobalt bearing a terminal η3-allyl ligand are susceptible to nucleophilic attack at different sites depending on the particular set of substituents, the central metal fragment, and the nucleophile. Attack of enolates, cuprates, acetylides, or heteroatom nucleophiles like phosphanes at the metallacyclic perimeter of the iron complexes 18 provides an easy access to unsaturated organic products like 1,2- or 1,3-dienes, δ-lactones, and functionalized cyclopentenones through novel rearrangement or cascade pathways. Synthetic applications are described; factors governing reactivity/selectivity are discussed; X-ray analytical structures of novel metallacycles are provided.

Notes: The outcome of reactions of bis(phosphonio)isophosphindolide salts 1[X] and 6[X] (X- = Cl-, Br-, CF3SO3-) with silver salts AgY (Y- = CF3SO3-, CF3CO2-, CH3CO2-, 1/2 SO4-) depends strongly on the available anions X, Y. If X-, Y- = CF3SO3-, both mononuclear and dinuclear silver complexes are formed which exhibit either μ1,μ1(P) or μ2,η1(P) coordination of the cations 1, 6 to one or to both metals. In solution, dynamic equilibria between both types of products and free 1, 6 were detected by 31P-NMR spectroscopy. Mononuclear (4a, 7) and dinuclear (5a, 8) complexes were isolated as solvates with CHCl3 or THF. If X-, Y- = CF3CO2, only equilibrium mixtures between the free ligands and silver complexes and no isolable products were obtained. 31P-NMR investigations revealed a preference for the formation of dinuclear complexes. Anion metathesis and precipitation of AgX were observed for X- = Cl-, Br-. No coordination of 1, 6 to Ag+ took place in the case of Y- = CH3CO2-, SO42-. The formed complexes were characterised in solution by 31P- and in part by 109Ag-NMR spectroscopy. Complexes 7, 8 were further studied by single crystal X-ray diffraction which revealed the presence of a THF molecule coordinated to silver in both cases. The μ2-coordinated cation 1 is the only bridging ligand in 8, whereas the presence of additional μ2-CF3CO2 ligands was deduced from the results of 31P,31P EXSY measurements in the case of the trifluoroacetato complexes.

Notes: The present article gives an account of the synthesis and structure as well as the spectroscopic and chemical properties of arsaalkenes R1As=CR2R3 and arsaalkynes RC≡As. Arsaalkenes are significantly less stable and more reactive than the corresponding phosphaalkenes. Only one kinetically stabilized arsaalkyne has been described so far.

Notes: tetrahedra-Tetrakis[tris(trimethylsilyl)methyl]tetraindane(4) (1) reacts with octacarbonyldicobalt to yield two products, depending on the stoichiometric ratio of the starting compounds: By replacement of one bridging carbonyl group a dicobalt monoindium derivative 2 is formed, which contains a Co—Co bond [256.81(5) pm] bridged by one carbonyl and one monoalkylindium group. While 2 is a monomer in benzene solutions, it dimerizes in the solid state by an interaction of the oxygen atom of the bridging carbonyl group to the coordinatively unsaturated In atom of a second molecule across a center of symmetry. Another compound (3) is formed by the replacement of both bridging carbonyl ligands, which exhibits a strongly distorted Co2In2 tetrahedron with normal Co—In bond lengths of 253.44(6) pm, but long Co—Co [280.14(6) pm] and In—In distances [336.18(6) pm].

Notes: Cyclobutene, bicyclobutane, and 1,3-butadiene are valence isomers within the concept of the Woodward-Hoffman rules. According to thermochemical considerations and in agreement with energy optimized quantum-chemical calculations at the ab initio RHF and MP2/6-31G(d,p) levels bicyclobutane is the least and 1,3-butadiene the most stable valence isomer. Phosphorus substitution exerts a considerable effect on the relative stabilities of the various valence isomers. Bicyclobutanes containing phosphorus atoms in the bridgehead positions are considerably more stable than the other phosphorus-substituted valence isomers. This conclusion was confirmed by an analysis of the natural bond populations.

Notes: After a brief review of previous work the results of the metathesis reaction between Ni(dme)Br2 and R2P(O)NR′Li [R = tBu, iPr, Ph; R′ = Et, Pr, iPr, (±)-sBu, tBu, tPen, Cy, Ph, (-)-α-methylbenzyl = Mb, 1-adamantyl = Ad] are reported. Complex formation occurred only with lithiated amides of tert-butylphosphinic acid, and bischelates [tBu2P(O)NR′]2Ni were obtained when R′ = sBu, Mb, tPen, Ad (1d - g). With R′ = Et, Pr bischelation was incomplete. Vis spectroscopy showed the paramagnetic compounds 1d - f to be planar in the solid state but tetrahedral in solution. 1g is tetrahedral in both phases. The planar structure of 1f was confirmed by X-ray single-crystal analysis (monoclinic, space group P21/n). The magnetic moments μeff of 1d, e, g are ca. 3.2-3.5 μB in both phases and the Curie-Weiss law is obeyed in the range 293-183 K. The same is valid for dissolved 1f. The μeff values of solid 1f are however, strongly temperature-dependent, varying from 1.38 to 0.55 μB (300-90 K). NMR data (31P, 1H, 13C) are reported. Obviously, a favorable combination of electronic and steric factors of substituents R and R′ produces with ligands [R2P(O)NR′]- the donor quality necessary for bischelation as well as the singular field strength required for the formation of planar paramagnetic species. As the combination of paramagnetism and planarity is bound to the solid state, lattice energy effects may be finally decisive for this unique constellation of tetracoordinated NiII complexes.

Notes: NMR studies of the reaction of complexes of the type (L-L)MoO(O2)2 (L - L= bidentate ligand) with strong Brønsted and Lewis acids prove that protons are transferred preferentially to an η2-peroxo and not to the oxo ligand. This behavior in proton transfer reactions is one critical point of the catalytic activity of such complexes in olefin epoxidation. EH calculations on the model complex (NH3)2MoO(O2)2 support the spectroscopic investigations.

Notes: Tetrakis[bis(trimethylsilyl)methyl]digallane(4) (1) reacts with tert-butyl or aryl=isocyanides [aryl = phenyl, o-methylphenyl, o-methoxyphenyl, p-methoxyphenyl) by a twofold insertion of the central carbon atoms into the Ga-Ga bond and formation of C-C single bonds. 1,4-Diazabutadiene derivatives bound to two R2Ga groups are formed (2-6), which in contrast to an aluminium analog exhibit only weak interactions between the imine nitrogen atoms and the coordinatively unsaturated gallium atoms as indicated by NMR spectroscopy and the long Ga-N distances in the molecular structures of three products: 2 (R = C6H5), 4 (R = o-MeOC6H4), and 6 (R = CMe3).

Notes: Irradiation of methanolic cadmium sulfide suspensions in the presence of Schiff bases and cyclopentene opens an easy access to new γ,δ-unsaturated amines. Their formation can be described as a kind of paired photoelectrolysis induced by the photogenerated electron-hole pair trapped at reactive surface sites of CdS. At the reductive site the imine is converted to an α-aminobenzyl radical by a proton-coupled electron transfer, while at the oxidative site cyclopentene is transformed to the cyclopentenyl radical through deprotonation of the intermediate radical cation. C-C coupling of these radicals affords the addition products. Competitive dimerisation of the radicals produces hydrodimers of the imines and dehydrodimers of the olefin, as demonstrated in the case of 1-phenylcyclohexene. Using optical active imines, we found no significant diastereoselectivity. In the absence of an olefin the alcoholic solvent was added to the imine. The molecular structure of one hydrodimer was resolved by X-ray analysis. When CdS/Pt was used as photocatalyst, hydrolysis products of the imine were formed, suggesting involvement of an intermediate OH radical.

Notes: The complexes [Ln(Ph2pz)3 (DME)2] and [Ln(tBu2pz)3 (DME)] (Ln = La, Nd, Er; Ph2pzH = 3,5-diphenylpyrazole; tBu2pzH = 3,5-di-tert-butylpyrazole; DME = 1,2-dimethoxyethane) have been prepared by reaction of the lanthanoid metal with bis(pentafluorophenyl)mercury and the pyrazole in DME. The molecular structures of [Er(Ph2pz)3 (DME)2] (3) and [Nd(tBu2pz)3 (DME)]∞ (5) have been determined by X-ray diffraction. Complex 3 has nine-coordinate Er with three chelating Ph2pz ligands and one chelating and one η1-bound DME. There is a trigonal prismatic arrangement of the oxygen donors and the centres of the N - N bonds. 5 was found to be a linear polymer with transoid DME ligands bridging Nd(tBu2pz)3 units in a novel manner. The centres of the N - N bonds (which are essentially coplanar with Nd), and the oxygen donor atoms adopt an arrangement intermediate between trigonal-bipyramidal and square-pyramidal [O - Nd - O 153.5(2)°].

Notes: By a variation of the nature of the reagent system conjugate addition to the cross-conjugated steroidal dienone 1 occurs selectively either at C-1 or at the sterically hindered C-5. With Me3Al or Me4AlLi in the presence of catalytic amounts of Cu1 salts, a high regioselectivity (up to 97:3) in favour of position 1 is achieved. Application of ate complexes of aluminium and titanium in the presence of Ni(acac)2 as catalyst, however, leads to a reversal of the regioselectivity in favour of position 5 (up to 11:89). Aluminium and titanium ate complexes are efficient reagents in the Ni(acac)2-catalysed conjugate addition to sterically hindered enones.

Notes: Complexes with Metal-Phosphorus Triple Bonds as Possible Intermediates in the Reactions between Chlorophosphinidenes and Metalates of Various Transition MetalsThe reaction of [{M′(CO)5}2PCl] (M′ = Cr, W) with various metalates ([Cp′Mo(CO)3]-, [Cp * Ni(CO)]-, [Cr2(CO)10]2-) yields the M2P2 tetrahedral complexes [(MLn)2(μ,η2- P2){M′(CO)5}2] (MLn = Cp*Ni, M′= Cr (1), W (2); MLn = Cp′Mo(CO)2, M′ = Cr (4); Cp* = η5-C5Me5, Cp* = η5C5H3tBu2) and the cyclo-P4 compound [{Cr(CO)4}(η4-P4){Cr(CO)5}4] 6. As side products the distorted prismane [(Cp*Ni)2{μ4,η4-(P2-O-P2)}{W(CO)5}2] 3 and the diphosphino-methanone complex [{Cp′Mo(CO)2}2{μ4η2-PC(O)P}-{Cr(CO)5}2] 5 are formed. The complexes are characterised by NMR, IR, MS, and X-ray structure analysis (1-5). Studying the reaction pathway provided evidence of phosphido intermediates of the type [LnM≡P→M′Ln].

Notes: Chiral Tripodal Ligands Bearing a Phosphite Donor Group: Synthesis and Coordination ChemistryThe mechanism of the reaction of epichlorohydrine (H-CH2Cl) (1) with lithium phosphides is analysed. A neighbouring-group mechanism has been found to be the essential driving force in this reaction. Monophosphanyl alcohols such as HOCH(CH2P(Ph)2)(CH2Cl) (2) and epoxides (Ph)2PCH2- (3) are characterized as intermediates. The mechanism leads to a rapid one-pot method for the synthesis of chiral racemic as well as enantiomerically pure bis(phosphanyl) alcohols HOCH(CH2PR2)(CH2PR2′) (4). The resulting bis(phosphanyl) alcohols 4 react easily with X2PCl (X = Cl; Ph; or X2 = 1,2-ethanedioxy-2,2′-biphenyldiyldioxy-) to yield the mixed donor group tripodal ligands X2POCH(CH2PR2)(CH2PR′2) (5, 6) containing both phosphite, phosphinite or phosphorodichloridite and phosphane donor groups. The identity of these compounds were proved by 1H-, 31P- and 13C-NMR spectroscopy, mass spectra, microanalysis as well as X-ray analysis. The coordination capabilities of these novel ligands are demonstrated by the synthesis and characterization of a (cyclooctadiene)rhodium complex {[(5c)Rh(I)COD]PF6} (7) of the ligand 5c, exhibiting the typical hetero-bicyclooctane tripod metal cage of this type of tripod complexes.

Notes: The highly reactive silyl triflates R4-nSi(OSO2CF3)n are valuable materials in organosilicon chemistry. Numerous new triflate derivatives of mono-, oligo-, and polysilanes were prepared by stepwise substitution of trifluoromethylsulfonyl groups for phenyl groups or other leaving groups. Conversions of silyl triflates with nucleophiles proceed regioselectively and, in most cases, quantitatively at low temperatures with short reaction times. Therefore, silyl triflates are suitable reagents for the synthesis and functionalization of linear and cyclic oligosilanes. Novel polycarbosilanes, polysilylalkynes, and polysilylphenylenes, which show a regular alternating arrangement of silylene groups and organic units, were prepared from α,ω-bis[(trifluoromethylsulfonyloxy)silyl]-substituted compounds and dinucleophiles. Branched polysilanes and polysilynes were obtained by reductive coupling of polymeric silyl triflates with potassium-graphite.

Notes: Bis(dichlorosilyl)amine reacts in chloroform solution with 2-picoline to give H3SiCl, H2SiCl2, and HSiCl3, whereas with 3-picoline the two hypervalent silicon compounds H2SiCl2-(3pic)2 and [H2Si(3pic)4]Cl2 · 4 CHCl3 containing hexacoordinated Si atoms are formed. These complexes are in a chemical equilibrium with each other in chloroform solution, from which crystals of [H2Si(3pic)4]Cl2 · 4 CHCl3 could be isolated. The crystal structure of the latter was determined by single-crystal X-ray diffraction. The complex can be regarded as an “contact ion trio” of [H2Si(3pic)4]2+ and two Cl- ions. The N-Si bond lengths, r(Si-N) = 196.9(3) and 197.5(3) pm, are similar to those found in neutral hexacoordinated Si complexes. The data obtained from a 1H1H ROESY experiment suggest that dissolution has no significant impact on the molecular structure of [H2Si(3pic)4]Cl2 · 4 CHCl3.

Notes: The coordination chemistry of the four oxa-crowned derivatives of dithiomaleonitrile mn-12S2O2, mn-15S2O3, mn-18S2O4, and mn-21S2O5 as well as of the acyclic bis(methylthio)maleonitrile mn-S2 with AgI was investigated by X ray structural and spectroscopic methods. The 2:1 complexes (ligand/AgI) [Ag(mn-12S2O2)2]PF6, [1]PF6, [Ag(mn-15S2O3)2]PF6, [2]PF6, and [Ag(mn-S2)2]PF6, [6]PF6, and the 1:1 complexes [Ag(mn-15S2O3)]ClO4, [3]ClO4, [Ag(mn-18S2O4)]PF6, [4]PF6, and [Ag(mn-21S2O5)]PF6 [5]PF6, were obtained with AgPF6 or AgClO4 in MeOH. The stoichiometry of the macrocyclic AgI complexes and the coordination mode of mn-S2On+1 coronands (n = 1-4) is determined by the length of the macrocyclic oligoethylene chain. - The mn-crown dithioethers mn-12S2O2 and mn-15S2O3 form with AgPF6 the new sandwich complexes [Ag(mn-12S2O2)2]PF6, [1]PF6, and [Ag(mn-15S2O3)2]PF6, [2]PF6. [1]PF6 crystallises in the triclinic space group P1. In the centrosymmetric cation [1]+ each mn-12S2O2 ligand is coordinated to the AgI centre in an endo manner via both S atoms and one O atom. The distance of the second O atom of mn-12S2O2 to AgI is somewhat longer than a normal Ag-Oether bond. The overall environment around AgI in [1]+ is that of a distorted cubic S4O4 set of donors. [2]PF6 crystallises in the monoclinic space group C2/c. In the centrosymmetric cation [2]+ silver(I) is planar-coordinated by the four S atoms of both mn-15S2O3 molecules. The six O atoms of both mn-15S2O3 ligands show only long-range interactions to the AgI ion. They surround AgI almost vertically to the planar S4 set of donors in a crown-like manner. - The crystal structures of the 1:1 complexes [Ag(mn-18S2O4)]PF6, [4]PF6, and [Ag(mn-21S2O5)]PF6, [5]PF6, consist of linear chain polymers. [5]PF6 forms an N-bridged chain polymer of endocyclic [Ag(mn-21S2O5)]+ units with S1O4NNitrile coordination at the AgI centre. In the 2:1 complex [Ag(mn-S2)2]PF6, [6]PF6, each mn-S2 acts as a monodentate NNitrile donor. - 13C-NMR studies in nitromethane solution confirm that the AgI ions in the complexes of the mn-crown dithioethers remain coordinated. However, the AgI ion in complex of mn-S2 is decoordinated.

Notes: Metal π Complexes of Benzene Derivatives, 49. - Halfsandwich Complexes of Trimesitylborane Mes3B: Synthesis and Structure of Mes2[B(η6-Mes)Cr(CO)3], MesB[η6-MesCr(CO)3]2, and B[η6-MesCr(CO)3]3. Redox Behavior and Questions of Intramolecular InteractionReactions of trimesitylborane (15) with hexacarbonylchromium (16), under varying conditions of stoichiometry and duration, afford the halfsandwich complexes 15[Cr(CO)3] = 17, 15[Cr(CO)3]2 = 18 and 15[Cr(CO)3]3 = 19, which have been characterized by X-ray structure analysis. As for the free ligand 15, the propeller shape of the complexes 17-19 induces chirality; the respective unit cells contain both enantiomers. The steric demand of the Cr(CO)3 fragments causes significant structural changes of the Mes3B unit: in 17 and 18 the bond lengths B-C are increased and the C-B-C bond angles in the reference plane ER1, which is spanned by the three carbon atoms bonded to boron, deviate from 120°; the largest differences was observed for 18. Coordination of Cr(CO)3 fragments to 15 leads to increased dihedral angles between the reference plane ER1 and the mesityl planes; the values of 50.1° for 15 and 61.8° for 19 are representative. Because of the lower symmetry within 17 and 18, the dihedral angles differ; a maximum of 71.1°, relative to the reference plane, is assumed by the noncoordinated ring of 18. The main objective of the study of 17-19 relates to the question of intermetallic communication between moieties separated by sp2-hybridized boron. According to IR data, interaction between the Cr(CO)3 units appears to be minimal. Cyclovo-Itammetry is more revealing: boron-centered reduction, which occurs at -1.94 V for 15, involves anodic shifts E1/2 (0/-) of + 0.24 ± 0.04 V per Cr(CO)3 unit for 17, 18 and 19. This trend is surprising since with increasing degree of coordination the dihedral angles also increase and, therefore, conjugation between the B(2pz) orbital and the mesitylene π systems decreases. Consequently, the redox shifts reflect competition between conjugative and inductive effects, the latter exceeding the former. Subsequent reduction to the dianions 172- -192- is quasi-reversible at -50°C. Chromium-centered oxidation in the +1 V region yields CV waves that fail to reveal resolved redox splitting δE1/2 between subsequent redox steps. However, based on the current ip(0/-) of one electron reduction, the peak currents for the oxidations of 17, 18 and 19 represent one-, two- and three-electron processes, respectively. Although these waves deviate from ideal reversibility, a gradual shift to more positive potentials and an increase in peak separation is discernible. From these features, the value δE1/2 ≤ 70 mV for subsequent oxidation processes at 18 and 19 may be derived as a crude estimate, attesting to weak interaction between the Cr(CO)3 moieties. The radical anions 15-•, 17-•, 18-• and 19-• were generated electrochemically and studied by means of EPR spectroscopy. The hyperfine coupling constants a(11B) increase in the order 17-• 〈 18-• ≤ 15-• 〈 19-•, which again demonstrates the action of stereoelectronic effects. Proton hyperfine coupling is resolved only for the radical anion 15-• of the free ligand. This implies that for the complex radical anions 17-• -19-•, due to the larger angles between the B(2pz) orbital and the z axes of the mesitylene π systems, conjugation Blarr;mesitylene is diminished. The UV/Vis spectra of 17-19 exhibit MLCT bands, which, relative to (η6-C6H6)Cr(CO)3 (λ = 317 nm), show large bathochrome shifts [λ (17) = 458 nm]. The additional shifts effected by introducing a second and third Cr(CO)3 unit are small however [λ (18) = 491 nm, λ (19) = 516 nm]. The energies ΔEop of the MLCT transitions may be compared to the differences ΔEcv = E1/2 (+/0, metal-centered) - E1/2(0/-, ligand-centered), the quantity δE = ΔEop - ΔEcv representing χout the outer-sphere reorganisation energy. For 17-19, the value δE = 0.18 ± 0.1 eV is thus obtained. Interestingly, for p-Me2NC6H4BMes2 δE = 0.29 eV has been reported, suggesting a similarity between a Me2N substituent and a Cr(CO)3 fragment bound to tris(aryl)borane.

Notes: The [(SePPh2)2N]- ligand 1c forms stable tris(chelates) with the SbIII, BiIII, and InIII ions. The crystal and molecular structures of the resulting compounds 3, 4, and 5 were determined by X-ray diffractometry. The coordination geometry around the metal centers can be described as a distorted octahedron. This feature and the results obtained by comparing the structures with their sulfur and oxygen analogs lead us to conclude that in both SbIII and BiIII compounds the arrangement around the metals suggests a stereochemically nonactive electron lone pair.

Notes: Selenophosphinito complexes (OC)4Mn(η2-Se\documentclass{article}\usepackage{amsmath}\pagestyle{empty}\begin{document}$ \dddot - $\end{document}PR21) (2a, b) [R1 = cyc-Hex (a), tBu (b)] are formed by the reaction of BrMn(CO)5 with the phosphane selenides R21HPSe (1a, b) in the presence of the auxiliary base Et(iPr)2N. According to an X-ray structural analysis, 2a crystallizes in the space group \documentclass{article}\pagestyle{empty}\begin{document}$ P\bar 1 $\end{document} with Z = 2. The dimeric complex [(OC)4Mn(μ-Se\documentclass{article}\usepackage{amsmath}\pagestyle{empty}\begin{document}$ \dddot - $\end{document}PMe2)]2 (4c) is not obtained in a straightforward way. Compound 4c is only obtained via the intermediate Br(OC)4Mn-Se\documentclass{article}\usepackage{amsmath}\pagestyle{empty}\begin{document}$ \dddot - $\end{document}P(H)Me2 (3c) by HBr elimination with nBuLi. Complex 3c is formed by replacement of carbon monoxide in BrMn(CO)5 by Me2HPSe (1c). A dissociative equilibrium between [(OC)4 Mn(μ-Se\documentclass{article}\usepackage{amsmath}\pagestyle{empty}\begin{document}$ \dddot - $\end{document}PMe2)]2 (4c) and the monomeric species (OC)4Mn(\documentclass{article}\usepackage{amsmath}\pagestyle{empty}\begin{document}$ \dddot - $\end{document}2-Se\documentclass{article}\usepackage{amsmath}\pagestyle{empty}\begin{document}$ \dddot - $\end{document}PMe2) was not observed. The cyclocotrimerization of the 〉P\documentclass{article}\usepackage{amsmath}\pagestyle{empty}\begin{document}$ \dddot - $\end{document}Se function with the activated alkynes ZC≡CZ [Z = CO2R2; R2 = Me (d), Et (e), iPr (f), cyc-Hex (g)] was successful only in the case of the cyclohexyl derivative 2a to give the selenaphosphamanganabicycloheptadienes 5d - g. An X-ray structural analysis proved that 5d crystallizes in the space group \documentclass{article}\pagestyle{empty}\begin{document}$ P\bar 1 $\end{document} with Z = 2. Under CO pressure 5d was degraded to the selenophene 6.

Notes: The reduction of the complex [(η5-C5H4)-ansa-(η5-C5H4)]TiCl2 with magnesium in the presence of Me3SiC2-SiMe3 in THF at room temperature gives the ansa-titanocone alkyne complex [(η5-C5H4)-ansa-(η5-C5H4)]Ti(η2-Me3SiC2-SiMe3) (ansa = Me2Si-O-SiMe2, 1). The similar pyridine-stabilized zirconium complexes could be obtained by analogous reactions and addition of pyridine: [(η5-C5H4)-ansa-(η5-C5H4)]Zr(L)(η2-Me3SiC2SiMe3) (ansa = Me2Si-O-SiMe2, L = pyridine: 2; ansa = SiMe2, L = pyridine: 3). All complexes were characterized by spectroscopic methods. An X-ray structure determination of complex 3 was conducted, and the data were compared to those of the complexes rac-(EB-HI)Zr(L)(η2-Me3SiC2SiMe3) [L = (S)-(-)-nicotine: 6, EBHI = ethylenebis(tetrahydroindenyl)] and Cp2Zr(py)(Me3SiC2-SiMe3).

Notes: The bisquaternary ammonium ozonides Me3N+(CH2)n +NMe3(O3-)2 with n = 3, 4, 6 (1, 2, 3), Me3N+(CH2)3+NMe3(O3-)2 · 3 NH3 (1a), Me3N+(p-Ph)+NMe3(O3-)2 (4) and Me3N+(p-Ph)+NMe3(O3-)2 · NH3 (4a) were obtained in quantitative yields by cation exchange starting from CsO3. The compounds 1a and 3 have been studied by single crystal X-ray analysis. The influence of C-H…O and N-H…O hydrogen bonds on the bond length and the bond angle of the ozonide anion is discussed; earlier results are included. The difference between the two bond lengths within the O3- ion [137.4(3) pm and 129.5(3) pm] in 1a is unexpectedly large. Thermal stabilities determined by DTA/TG methods range from 24-83°C.

Notes: The molecular zinc hydroxide complex TpCum,MeZn—OH [1, TpCum,Me = tris(3-cumenyl-5-methylpyrazolyl)hydroborate] is a powerful nucleophile. It effects stoichiometric hydrolysis of activated esters RCO—OX and amides RCO—NHX in nonaqueous media. The cleavage products are TpCum,MeZn—OCOR and HOX or H2NX, resp. Two of them (TpCum,MeZn—OCO—CH2-CH2OH resulting from propiolactone and TpCum,MeZnOCO—CF3 resulting from trifluoroacetamide) were characterized by crystal structure determinations.

Notes: The metal complexes (E,E)-[{diethyl 2,2′-[1,2-phenylenebis(iminomethylidyne)]bis[3-oxobutanoato]}(2-)-N,N′,O3,O3′]manganese (Mn1a), [3,3′]-[1,2-phenylenebis(iminomethylidyne)bis(2,4-pentanedionato)(2-)-N,N′,O2,O2′]manganese (Mn1b), and (Z,Z)-[diethyl 3,3′-(1,2-phenylenediimino)bis(2-cyano-2-propenoato)](2-)-N3,N3′,O1,O1′]manganese (Mn1c) were sythesised and the oxygenation of these complexes was investigated by gas volumetry. All complexes except Mn1c are able to take up oxygen but with different magnitudes. The catalytic activity of the Mn, Co, and Fe complexes of the ligands 1a and 1c and (E,E)-[{diethyl 2,2′-[1,2-ethylenebis(iminomethylidyne)]bis[3-oxobutanoato]} (2-)N,N′,O3,O3′] iron (Fe1d) and [diethyl (all-E)-5,14-dihydro-6,17-dimethyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecine-7,16-dicarboxylato)(2-)-N5,N9,N14,N18]iron (Fe2a) has been compared with respect to the oxidation of hydroquinone by molecular oxygen. The results are interpreted with the aid of electrochemical properties, Lewis acidities, and other relevant factors. However, no simple relationship between the catalytic activity and the other factors could be found.