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1

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Chiral Chelate Ligands Based on a Neopentane Framework; Introducing Indenyl and Fluorenyl Donor Groups (1999)

Vogelgesang, Joachim ; Huttner, Gottfried ; Kaifer, Elisabeth ; [et al.]

Weinheim : Wiley-Blackwell

Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2187-2199

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ISSN: 1434-1948

Keywords: Ansa compounds ; Cp-derived chelate ligands ; Neopentane chemistry ; Spiro compounds ; Tripodal ligands ; Cyclopentadienyl compounds ; Chemistry ; General Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The neopentane-derived functionalized oxetane O(CH2)2C(CH3)(CH2OMs), 1, reacts with indenyllithium (LiInd) or fluorenyllithium (LiFlu) to produce the derivatives O(CH2)2C(CH3)(CH2R) (R = indenyl, fluorenyl), 2. The oxetane ring of 2 undergoes nucleophilic ring-opening by reaction with LiPR′2 to give the chiral chelate ligands (HOCH2)(CH3)C(CH2R)(CH2PR′2) (R = indenyl, fluorenyl), 5. Nucleophilic ring-opening by LiInd or LiFlu is possible too, resulting in the functionalized ansa-Cp ligands (HOCH2)(CH3)C(CH2R)(CH2R′) (R, R′ = indenyl, fluorenyl), 12. Electrophilic ring-opening of 2 with HBr to give (HOCH2)(CH3)C(CH2R)(CH2Br) (R = indenyl, fluorenyl), 3, is also possible. The alcohol function of 3 may be activated directly, whereas activation of this group in 5 is only possible after BH3 protection of the phosphane function. The mesylates (MsOCH2)(CH3)C(CH2R)(CH2Br) (R = indenyl, fluorenyl), 4, undergo, under basic conditions, spiro cyclization to produce spirocyclobutane derivatives 9 with the α-carbons of the five-membered cycles acting as the spiro centres. Substitution of the mesylate group of 4 by PR2 nucleophiles is therefore not possible. Ansa-Cp derivative (MsOCH2)(CH3)C(CH2Ind)(CH2Flu), 12c also reacts with LiPPh2 with spiro cyclization to produce 9d, instead of giving the substitution product. Tripodal ligands (CH3)C(CH2R)(CHPPh2)2 (R = indenyl, fluorenyl), 11, are accessible by the reaction of (MsOCH2)(CH3)C(CH2PPh2)2 with LiInd or LiFlu. All compounds are fully characterized by the usual spectroscopic and analytical techniques including single-crystal X-ray analyses in several cases.

Additional Material: 6 Ill.

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2

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Neopentane-Based Tripodal CpL2 Ligands: Synthesis and Reactions of CH3C(CH2-η5-C5H4)(CH2-η1-PPh2)2RuCl; Hindered Rotation of Vinylidene Ligands (2000)

Urtel, Katrin ; Frick, Axel ; Huttner, Gottfried ; [et al.]

Weinheim : Wiley-Blackwell

Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 33-50

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ISSN: 1434-1948

Keywords: Tripod ligands ; Hindered rotation of vinylidene ligands ; CpML2 chelate ligands ; Ruthenium ; Carbenes ; Carbene-type ligands ; Cyclic voltammetry ; Chemistry ; General Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The tripodal ligand [CH3C(CH2C5H4)(CH2PPh2)2]- reacts with RuCl2(PPh3)3 to produce CH3C(CH2-η5-C5H4)(CH2-η1-PPh2)2RuCl, [tripodCpL2RuCl], 1. Complex 1 undergoes substitution of the chlorine function with various nucleophiles L′ to produce [tripodCpL2RuL′]+. The carbonyl derivative (L′ = CO) 2, isonitrile (L′ = RNC) 3, nitrile compounds (L′ = RCN) 4, and a tolane adduct (L′ = η2-PhC≡CPh) 5 are obtained when 1 is treated with the appropriate ligands in polar solvents. Halide acceptors (e.g. TlPF6) are generally needed to promote these reactions. The cyanide derivative tripodCpL2RuCN (3a) is alkylated by F3CSO3CH3 to give the isonitrile derivative [tripodCpL2RuCNMe]+3b. Terminal alkynes HC≡CR produce vinylidene compounds [tripodCpL2RuL′]+, where L′ = C=CHR (R = tBu, 7b; R = Ph, 7c), or allenylidene derivatives, L′ = C=C=CPh2 (6), depending on the nature of R (R = CPh2OH for synthesis of 6). Trimethylsilylacetylene gives the parent vinylidene species, L′ = C=CH2 (7a), which is transformed to the Fischer-type carbene compound, L′ = C(OMe)Me (8), upon treatment with methanol. The vinylidene species 7 are deprotonated by NaOMe to produce the alkynyl compounds tripodCpL2RuC≡CR (9). Methylation of 9 with F3CSO3CH3 results in the vinylidene derivatives L′ = C=C(Me)R (R = tBu, 7d; R = Ph, 7e), having two organic substituents at the terminal carbon centre. For all vinylidene compounds with two different substituents at their terminal carbon atom, hindered rotation of the single-faced vinylidene π-ligand about its Ru-C bond is observed. Analysis by 31P-NMR spectroscopic coalescence measurements as well as line-shape analyses reveals activation enthalpies of around 40 kJmol-1 for this rotation, with small activation entropies of around ±10 Jmol-1K-1. Solid-state structures of nine compounds of the type [tripodCpL2RuL′]+n (n = 0, 1) demonstrate the remarkable conformational rigidity of the tripodCpL2Ru template. They also show that the possible strain imposed by linking the Cp ligand and the two donor groups L in one and the same chelate scaffolding does not appear to impose a serious steric strain on these templates.

Additional Material: 4 Ill.

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3

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Synthesis of the Germanium(I) Compounds [Ge2Hal4]2- and Their Reductive Condensation to Octahedral [Ge6]2- Clusters in an Organometallic Environment (2000)

Renner, Gerd ; Kircher, Peter ; Huttner, Gottfried ; [et al.]

Weinheim : Wiley-Blackwell

Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 879-887

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ISSN: 1434-1948

Keywords: Germanium(I) ; Tetrahalgenodigermanate(2-) ; Octahedral [Ge6]2- clusters ; Organometallic derivatives ; Carbonyl complexes ; Chromium ; Tungsten ; Chemistry ; General Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: GeI2 reacts with [M2(CO)10]2- (M = Cr, W) leading to reductive coupling of two GeI2 units to produce the [Ge2I4]2- ligands of [{(OC)5M}I2Ge-GeI2{M(CO)5}]2- (1a and 2a). The [Ph4P] salts of these anions have been characterised by X-ray structure analyses as have the [Ph4P] salts of [{(OC)5M}Cl2Ge-GeCl2{M(CO)5}]2- (1b and 2b) obtained from the iodo derivatives 1a and 2a by halide metathesis with [Ph4P]Cl. Treatment of GeI2 with [W2(CO)10]2- in the presence of 2,2′-bipyridine leads to [{(OC)5W}I2Ge-Ge(bipy){W(CO)5}] (3). The digermanium ligands in 1-3 contain germanium in the unconventional formal oxidation state +I. Reductive condensation of [{(OC)5Cr}I2Ge-GeI2{Cr(CO)5}]2- (1a) by addition of [Cr2(CO)10]2- leads to the octahedral cluster [{(OC)5Cr}6Ge6]2- (4) in a yield of 40%. The sequence of reactions as reported describes the first systematic approach to the synthesis of [E6]2- clusters.

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4

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Preparation of Enantiomerically Pure Chelate Ligands L2 = XCH2CH(OH)CH2Y from Epichlorohydrin - Conformation of Their L2Rh(COD)+ Derivatives and Enantioselective Hydrogenation by L2Rh(COD)+ (1999)

Karas, Jörg ; Huttner, Gottfried ; Heinze, Katja ; [et al.]

Weinheim : Wiley-Blackwell

Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 405-420

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ISSN: 1434-1948

Keywords: Epichlorohydrin ; Chiral diphos ligands ; Diphos rhodium complexes ; Conformation analysis ; Chelates ; Asymmetric synthesis ; Chemistry ; General Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Enantiomerically pure chelate ligands L2 = XCH2CH(OH)CH2Y (1) are obtained from epichlorohydrin in a two-step synthesis. × and Y may be different types of R2P donor groups, NR2 or SR donors. The OH function of 1 may be transformed into an ether function under specialized conditions. Ligands 1 react with [Rh(COD)Cl]2 in the presence of KPF6 to give the coordination compounds 2, [L2Rh(COD)]+PF6-, as orange, microcrystalline salts. The structures adopted by compounds 2 in the solid state have been analysed by X-ray crystallography in selected cases, and it has been found that the six-membered chelate cycles adopt twist as well as chair conformations depending on the nature of × and Y. In solution, compounds 2 generally show dynamic behaviour, which is in part due to the conformational flexibility of the six-membered cycles. In cases where one of the PR2 donor groups contains ortho-substituted phenyl substituents, rotational isomerism of these groups is an additional dynamic process. For some of these compounds, the nature of the dynamic behaviour has been analysed by variable-temperature NMR experiments. Compounds 2 are found to be precatalysts in the hydrogenation of (Z)-2-acetamidocinnamic acid. The rate of conversion is strongly influenced by the steric bulk of the substituents, with smaller substituents leading to higher rates. Enantiomeric discrimination is high only for those ligands that contain ortho-substituted aryl groups at their PR2 donors. The maximum enantiomeric excess observed was 85% for × = PPh2, Y = P(2-MeOPh)2.

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5

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η4-Coordination of Dienes and Heterodienes to the TripodCobalt(I) Template [CH3C(CH2PPh2)3Co]+: Synthesis, Structure, and Dynamics (1999)

Rupp, Rolf ; Frick, Axel ; Huttner, Gottfried ; [et al.]

Weinheim : Wiley-Blackwell

Berichte der deutschen chemischen Gesellschaft 2000 (1999), S. 523-536

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ISSN: 1434-1948

Keywords: Tripod ligands ; Dienes ; Heterodienes ; η4-Coordination ; Hindered rotation ; Line-shape analysis ; Chemistry ; General Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: CH3C(CH2PPh2)3CoCl (1) is easily accessible from CH3C(CH2PPh2)3CoCl2 by reduction with activated zinc powder. Upon dehalogenation with TlPF6, 1 reacts with dienes to give [tripodCoI-(η4-diene)]+ (2). The heterodienes acrolein and methyl vinyl ketone produce the analogous η4-heterodiene compounds 3. When crotonaldehyde is used as the potential η4-diene ligand, decarbonylation is observed leading to [tripodCoI-(CO)2]+ (4). Reaction of [tripodCoaq](BF4)2 with allyl mercaptan produces [tripodCoI-(η4-thioacrolein)]+ (3a) through dehydrogenation of the ligand precursor. 1,2-Diketones such as benzil and phenanthrenequinone do not coordinate in a η4 fashion but rather generate η2-coordinate enediolato ligands by an electron-transfer process, resulting in compounds of the type {tripodCoIII-[η2-RC(O)=C(O)R]}+ (5). All the compounds have been characterized by standard analytical and spectroscopic techniques, including X-ray analysis in some cases. Compounds 4 and 5 show trigonal-bipyramidal coordination in the solid state, whereas the coordination polyhedra in compounds 2 and 3 are better described as square-pyramidal. While a minimum of two phosphorus resonances might be expected for each of these coordination geometries, only one time-averaged signal is normally observed. Only with the η4-coordinated heterodienes acrolein, methyl vinyl ketone, and thioacrolein present in 3 is there a resolution of the signals of the three chemically distinct phosphorus nuclei at low temperatures. By 31P-NMR line-shape analysis, the activation barriers for the rotational reorientation of the heterodienes are found to be around ΔH≠ = 47 kJmol-1 for all three compounds 3.

Additional Material: 8 Ill.

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