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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2147-2156 
    ISSN: 1434-1948
    Keywords: Tetrapodal pentadentate ligand ; Ligand periphery ; Polydentate amine complex ; Nickel ; Podand ; Schiff base ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The tetrapodal pentaamine ligand 2,6-bis(1′,3′-diamino-2′-methylprop-2′-yl)pyridine (1), which contains four equivalent primary amino groups, can be derivatised partly or completely by Schiff base condensation with suitable carbonyl compounds. The new ligands thus obtained are mononucleating, as shown by the X-ray crystal structures of their respective nickel(II) complexes. Reaction of 1 with 1 equiv. of salicylaldehyde and subsequent reduction allows the selective modification of one of the four sidearms. The resulting ligand 2 is hexadentate and uninegative in its nickel(II) complex {[(2)Ni]PF6} (3) with both the secondary amine and the phenoxide functionalities coordinated to the metal centre. The unreduced Schiff base form of the ligand, 4, does not form a complex with nickel(II) as readily, and only a small quantity of the mixed salt {[(4)Ni][(1)Ni(H2O)](Br)2(PF6)} (5)has been obtained. While the overall coordination of 4 resembles that of 2, there is considerably more strain in the appended chelate ring, due to the presence of the C=N double bond. Modification of one arm in 1 can also be achieved by condensation with 1 equiv. of acetylacetone, to give the new ligand 6 which, likewise, is hexadentate in its NiII complex {[(6)Ni](PF6)2} (7). In this case, however, the N/O-functional sidearm is not deprotonated. Rather, it is coordinated as the keto-imine tautomer, making 7 a rare example of a metal complex containing this structural fragment. Two-fold functionalisation of 1 is observed upon reaction with acetone, regardless of whether the ketone is present in stoichiometric amounts or in excess, to give the pentadentate ligand 8with two diagonally juxtaposed isopropylidene-imine units. The complex isolated with this ligand {[(8)Ni](PF6)2} (9) contains pentacoordinate NiII, the sixth coordination site being blocked by the rigidly positioned isopropylidene groups. When reacted with 4 equiv. of trans-cinnamaldehyde, all the primary amino groups in 1 condense to give the four-fold Schiff base 10, which acts as a pentadentate podand towards nickel(II). In this complex, {[(10)Ni(OH2)]Br2} (11), an aqua ligand completes the coordination octahedron. All ligands are stable towards hydrolysis when coordinated to the metal, despite the presence of alkyl-imine groups in some cases.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 59-63 
    ISSN: 1434-1948
    Keywords: Phosphorane imine ; Sulfur ligands ; Nickel ; Palladium ; Platinum ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of the trinuclear [M(′S3′)]3 complexes {M = Ni (4), Pd (5), Pt (6); ′S3′2- = bis(2-mercaptophenyl)sulfide (2-)} with HNPnPr3 yielded the new phosphorane imine complexes [M(NHPnPr3)(′S3′)] {M = Ni (1), Pd (2), Pt (3)}. The complexes 1-3 have been completely characterized and are rare examples of mononuclear phosphorane imine complexes with late transition metals. Spectroscopic and structural results indicate that the HNPnPr3 ligands favor the ylidic structure when binding to [M(′S3′)] fragments. X-ray structure determinations showed that [M(NHPnPr3)(′S3′)] complexes associate through N-H···S(thiolate) bridges to give centrosymmetric dimers.
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  • 3
    ISSN: 1434-1948
    Keywords: Ruthenium ; S ligands ; Hydrazine ; Diazene ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the search for ruthenium complexes with sulfur-dominated coordination spheres that bind, activate, or stabilize nitrogenase relevant molecules, complexes containing the new and robust tetradentate ligand ‘tpS4’-H2 were synthesized. Treatment of [RuCl2(PPh3)3] with ‘tpS4’2- gives [Ru(PPh3)2(‘tpS4’)] (1), which contains two labile PPh3 ligands. The reaction of 1 with PEt3 or DMSO led to substitution of both PPh3 ligands, yielding [Ru(PEt3)2(‘tpS4’)] (2) and [Ru(DMSO)2(‘tpS4’)] (3), respectively. When treated with nitrogenous ligands, complex 1 lost only one PPh3 ligand to yield [Ru(L)(PPh3)(‘tpS4’)] complexes where L = py (7), NH3 (8), N2H4 (9), NH2NHMe (10), and CH3CN (12), all of which are labile. The labile acetonitrile complex [Ru(CH3CN)(PPh3)(‘tpS4’)] (12) proved to be particularly suited as a precursor for the syntheses of other [Ru(L)(PPh3)(‘tpS4’)] complexes. The 18 and 19 valence electron NO complexes [Ru(NO)(PPh3)(‘tpS4’)]BF4 (13) and [Ru(NO)(PPh3)(‘tpS4’)] (14), (NEt4)[Ru(N3)(PPh3)(‘tpS4’)] (15), [Ru(I)(PPh3)(‘tpS4’)] (16), and [Ru(N3)(PPh3)(‘tpS4’)] (17) were obtained starting from complex 12. The labile mononuclear hydrazine complex [Ru(N2H4)(PPh3)(‘tpS4’)] (9) gave the dinuclear complex [μ-N2H4{Ru(PPh3)(‘tpS4’)}2] (18) by dissociation of hydrazine. The dinuclear diazene complex [μ-N2H2{Ru(PPh3)(‘tpS4’)}2] (19) was obtained by oxidation of 9 and more readily from [Ru(CH3CN)(PPh3)(‘tpS4’)] (12) and N2H2, which was generated in situ from K2N2(CO2)2 and acetic acid. The molecular structures of 7, 13, 16, 18, and 19 were determined by X-ray structure analyses. The complexes 18 and 19 represent the first complexes containing the hydrazine/diazene couple, which enables us to compare both the bonding features and the formation of N-H···S bridges when hydrazine and diazene bind to transition metal sulfur sites.
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  • 4
    ISSN: 1434-1948
    Keywords: Ruthenium ; Sulfur ligands ; Exchange reactions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In a quest for ruthenium complexes having [RuNS4] cores, a non-fluxional configuration, trans-thiolate donors, and exchangeable coligands L, [Ru(L)(‘pyS4’)] complexes have been synthesized [‘pyS4’2- = 2,6-bis(2-mercaptophenylthio)dimethylpyridine(2-)]. Treatment of [RuCl2(PPh3)3] with ‘pyS4’2- gave [Ru(PPh3)(‘pyS4’)] (1). Alkylation of 1 with excess MeI yielded [Ru(PPh3)(‘pyS4’-Me2)]I2 (2). [Ru(DMSO)(‘pyS4’)] (3) was obtained from [RuCl2(DMSO)4] and ‘pyS4’2-. The PPh3 or DMSO coligands in 1, 2, and 3 proved to be very inert to substitution. Only the DMSO could be displaced by CO under drastic conditions yielding [Ru(CO)(‘pyS4’)] (4). Treatment of [RuCl2(CH3CN)4] with ‘pyS4’2- yielded [Ru(‘pyS4’)]2 (5); in the presence of PEt3 or N2H4 mononuclear [Ru(PEt3)(‘pyS4’)] (6) and [Ru(N2H4)(‘pyS4’)] (7) were formed. Template alkylation of NBu4[Ru(NO)(S2C6H4)2] with 2,6-bis(tosyloxymethyl)pyridine gave [Ru(NO)(‘pyS4’)]Tos (8). Complex 8 proved to be the best suited precursor for L exchange reactions. Under reducing conditions, 8 releases its NO ligand and the resulting [Ru(‘pyS4’)] fragments can combine either with each other to give 5, or with PEt3 and N2H4 to yield 6 and 7, respectively. All complexes have been characterized by spectroscopic methods and elemental analysis; 1, 2, 3, and 4 have also been submitted to X-ray structure analysis.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 271-279 
    ISSN: 1434-1948
    Keywords: Nickel complexes ; Palladium complexes ; S ligands ; Exchange reactions ; Azide ; Sulfinylimide ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to obtain suitable precursors for nickel and palladium complexes that model the reactivity of the active sites of hydrogenases and CO dehydrogenases, a series of [M(L)(‘S3’)] complexes has been synthesized [M = NiII, PdII; ‘S3’2- = bis(2-mercaptophenyl)sulfide(2-)]. X-ray structure determinations of [Ni(‘S3’)]3 (1) and [Pd(‘S3’)]3 (2) have revealed that the [M(‘S3’)] fragments trimerize to give six-membered [MS]3 rings, which exhibit chair conformations with alternating MII centers and thiolate bridging atoms. Reactions of the parent complex [Ni(‘S3’)]3 (1) with nucleophiles L, such as thiolates SR- (R = tBu, Cy, Me, Ph), phosphanes PR3 (R = Cy, Ph), chloride, or azide, have been found to yield the corresponding anionic or neutral [Ni(L)(‘S3’)] complexes, which were isolated as (NBu4)[Ni(SR)(‘S3’)] [R = tBu (3), Cy (4), Me (5), Ph (6)], [Ni(PR3)(‘S3’)] [R = Cy (7), Ph (8)], (NBu4)[Ni(Cl)(‘S3’)] (9), and (NBu4)[Ni(N3)(‘S3’)] (10). When treated with Me3SiX, the StBu- ligand in (NBu4)[Ni(StBu)(‘S3’)] (3) was exchanged to give (NBu4)[Ni(X)(‘S3’)] [X = Cl- (9), N3- (10), NCS- (11), NSO- (12)]. The palladium complex [Pd(‘S3’)]3 (2) could also be cleaved with StBu-, but the resulting (NBu4)[Pd(StBu)(‘S3’)] (13) proved inert towards exchange reactions with Me3SiX. All the mononuclear complexes have been characterized by standard spectroscopic techniques and by elemental analysis. The molecular structures of 3, 4, 6, 7, 8, 9, and 13 have been determined by X-ray crystallography. The [MS3L] core geometries of all the complexes are non-planar, exhibiting a considerable tetrahedral distortion.
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  • 6
    ISSN: 0947-6539
    Keywords: dihydrogen activation ; heterolytic cleavage ; hydrido complexes ; rhodium ; S ligands ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [Rh(H)(L)(“buS4”)] complexes (L = CO (1), PCy3 (2); “buS4”2- = 1,2-bis[(2-mercapto-3,5-di-tert-butylphenylthio)ethane2-]) catalyze the D2/H+ exchange between D2 and EtOH protons in the presence of catalytic amounts of Brønsted acids. A mechanism and complete cycle for the heterolytic D2 cleavage are proposed that are based on characterization of key intermediates and monitoring of key reactions. The key intermediates are the thiol hydride complexes [Rh(H)(L)(“buS4”-H)]BF4, L = CO (3), PCy3 (4), the coordinatively unsaturated complexes [Rh(L)(“buS4”)]BF4, L = CO (5), PCy3 (6), which are the actual catalysts, and the deuterium-labeled derivatives of 1-4. Complexes 3 and 4 form from 1 and 2 by protonation with HBF4, and they release H2 to give 5 and 6. Complex 5 dimerizes in the solid state and was characterized by X-ray structure determination of 5·8CH2Cl2 (triclinic space group P\documentclass{article}\pagestyle{empty}\begin{document}$ \bar 1 $\end{document}, a = 1048.2(4) pm, b = 1430.0(5) pm, c = 1785.7(7) pm, α = 100.49(3)°, β = 102.92(3)°; γ = 103.68(3)°, Z = 1). Complex 6 is mononuclear and adds H2O or THF reversibly to give the highly labile [Rh(L)(PCy3)(“buS4”)]BF4, L = H2O (7), THF (8). CO is irreversibly added to give the stable [Rh(CO)-(PCy3)(“buS4”)]BF4 (9), whose high-frequency ν(CO) (2081 cm-1) indicates a relatively low electron density at the Rh center. Complex 6 also adds to H2 to give 4, which can be deprotonated by solid Na2CO3 or H2O to yield neutral 2. 1H NMR and 2H NMR spectroscopy revealed the scrambling of thiol protons and hydride ligands in 3 and 4 and its deuterium-labeled derivatives. This exchange of thiol protons for hydride ligands is explained by a transient [Rh(η2-H2)] species. Low-temperature 1H/2H NMR spectroscopy showed that protonation of 2 yields four diastereomers of 4 resulting from protonation of the four stereochemically nonequivalent lone pairs at the thiolate donors of 2. The relevance of these findings to H2 activation at transitionmetal sulfur sites in hydrogenases or hydrotreatment catalysts, and differences from the H2 cleavage achieved with other complexes not containing “built-in” Brønsted-basic centers, are discussed.
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  • 7
    ISSN: 1434-1948
    Keywords: Lead(1+) ; Indium(3+) ; Organylphosphanylamide complexes ; Phosphazene ; 207Pb-NMR spectra ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of PbCl2 with LiN(PPh2)2 (1) at -78°C affords the P-P coupled phosphazene Ph2P-N=PPh2-PPh2=N-PPh2 (2) as an oxidation product and, as a reduction equivalent, the novel lead(1+) complex [(Pb1+)2(μ-Ph2P···N···PPh2-)2](Pb-Pb) (3). The crystal structure determination of the red compound 3 shows a Pb-Pb bond length of 304.1(1) pm. The 31P- and 207Pb-NMR spectra of 3 are complicated due to the presence of a higher order spin system (AA′A′′A′′′X for the mono-207Pb isotopomer, AA′A′′A′′′XX′ for the bis-207Pb isotopomer). Simulations of the 31P and 207Pb spectra both on material with natural isotope abundance and on the 207Pb-labelled compound (3*) reveal a large Pb,Pb coupling constant of 7708 Hz, indicative of a covalent Pb-Pb bond. - Though InCl3 is diagonally related to PbCl2, no significant redox process is observed in the reaction between InCl3 and 1. The yellow crystals of [In3+(Ph2P···N···PPh2-)3] (4) that are obtained were also investigated by X-ray analysis. These show a propeller-like configuration of the three four-membered chelate rings with indium(3+) as the centre.
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  • 8
    ISSN: 1434-1948
    Keywords: S ligands ; P ligands ; Osmium ; Solvent effects ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In search for osmium complexes with sulfur-dominated coordination spheres that potentially bind and activate or stabilize nitrogenase relevant small molecules, several osmium-sulfur complexes containing 1,2-bis(2-mercaptophenylthio)ethane(2-) (′S4′2-) and benzenedithiolate (′S2′2-) ligands were synthesized. [OsII(PR3)2(′S4′)] [R = Ph (1), Et (2)], [OsIV(PR3)2(′S2′)2] [R = Et (3), Pr(4), Me(5), Ph(6)], [OsIV(PCy3)(′S2′)2] (7), (PHCy3)[OsIII(′S2′)2] (8a), (NMe4)[OsIII(′S2′)2] (8b), and (NBu4)2[OsIV(′S2′)3] (9b) were obtained in reactions starting from commercially available osmium compounds and the sulfur and phosphane ligands. The presence or absence of reducing solvents strongly influenced these reactions. Octahedral (3), (4), and (PHCy3)2[OsIV(′S2′)3] (9a) were characterized by X-ray structure analysis, leading to the conclusion that despite the high oxidation state of the osmium centers, innocent dithiolate ligands are present. The stabilization of the OsIV centers is traced back to S→M π donation. Close inspection of 1 and 2 revealed a large influence of the phosphane ligands on the stability of OsII thioether complexes. While 1 is reasonable stable, 2 readily gives 3 and ethylene via intramolecular ′S4′2- ligand reduction and OsIII→ OsIV oxidation. UV-Vis spectra of 3-5 indicate phosphane dissociation in solution leading to pentacoordinate [Os(PR3)(′S2′)2] complexes. This was confirmed by the synthesis of pentacoordinate [Os(PCy3)(′S2′)2] (7).
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  • 9
    ISSN: 1434-1948
    Keywords: Tetrapodal pentadentate ligand ; Square pyramidal coordination cap ; Pentaamine ; Nickel(II) complexes ; Magnetochemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The architecture of the tetrapodal pentaamine ligand 2,6-bis(1′,3′-diamino-2′-methylprop-2′-yl)pyridine (pyN4, 1) allows it to coordinate to nickel(II) as a square pyramidal coordination cap. The pyridine nitrogen atom occupies an apical position of the coordination octahedron, while four equivalent pendent primary amino groups occupy the equatorial positions, with a sixth coordination site remaining for a monodentate ligand. Exchange of this ligand is facile, and a series of complexes [(1)NiX]n+ (X = OH2, OClO3, NCS, N3, {Cl-Ni(pyN4)}) has been prepared and characterised by elemental analysis, IR and UV/Vis spectroscopies (as applicable), and X-ray structure determination. While the solid state structures show varying degrees of distortion of the ligand cap 1 from C2v symmetry, a polynucleating coordination mode has not been observed. The ligand enables the synthesis of dinuclear nickel(II) complexes containing a single bridging ligand, as exemplified by the singly -chloro bridged complex [(1)Ni-Cl-Ni(1)](PF6)3. This complex has an antiferromagnetically coupled ground state of total spin ST = 0, as determined from variable-temperature magnetic susceptibility measurements.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1951-1957 
    ISSN: 1434-1948
    Keywords: Rhodium catalysis ; C-C coupling ; C-H activation ; Alkynes ; Trisubstituted naphthalenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: RhCl(PPh3)3 in the presence of excess hydrochloric acid and azobenzene in refluxing 1-pentanol catalyzes the cyclodimerization of arylalkynes to 1,2,3-substituted naphthalene derivatives. This enables an easy access to 1,2,3-triphenylnaphthalene (1), 7-methoxy-1,2,3-tris(p-methoxyphenyl)naphthalene (2), 7-methyl-1,2,3-tris(p-methylphenyl)naphthalene (3), and 7-nitro-3-(p-nitrophenyl)-1,2-diphenylnaphthalene (4). A co-cyclodimerization of tolan with 4-octyne affords 3-phenyl-1,2-dipropylnaphthalene (5). The structure of 4 was resolved by single-crystal X-ray structural analysis. The rate of formation of 1 is first-order with respect to tolan and RhCl(PPh3)3 and exhibits activation parameters of ΔH
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