F. Carre

Introduction of optically active triorganogermyl ligands into transition metal complexes. Synthesis of carbene complexes, crystal structure and absolute configuration of cis-S(-)(methylphenyl-1-naphthylgermyl)-(methylethoxycarbene) tetracarbonylmanganese

The attachment of triorganogermyl ligands to transition metals by displacement of a CO ligand is described. The optical stability of the germyl anions has been used to prepare a nickel-germanium complex by displacement of chloride (this reaction representing a limiting case) and more generally in the synthesis of germanium-transition metal bonds by displacement of CO (the transition metal being Cr, Mo, W, Mn, Fe, or Co). Optically active germyl anions are used in the synthesis of carbene complexes by insertion of CO ligands into a carbon-transition metal sigma bond. A crystallographic study of the complex MePh-(1-Np)Ge(CO)4MnC(OEt)Me reveals that the carbene unit is cis to the germanium and that the germyllithium has reacted with retention of configuration.

Pentacoordinate silicon and germanium derivatives: molecular structure

Abstract The crystal structure of o-(Me2NCH2)C6H4GeMePhCl has been determined by single crystal X-ray diffraction study. The germanium atom has a distorted trigonal-bipyramidal (T.B.P.) geometry. The low temperature 19F NMR spectra of o-(Me2NCH2)C6H4SiMeF2 and o-(Me2NCH2)C6H4SiF3 are also consistent with a T.B.P. geometry. The stability of the T.B.P. structure is not determined by the apicophilicity of the fluorine atoms.

Problème du cation siliconium IV. Mécanisme de la coupure métal—carbone dans les dérivés β-fonctionnels du silicium et du germanium

Abstract Brominations of triphenylallylsilane, methylphenyl-1-naphthylallylsilane, 2(1-naphthyl)-2-allyl-1,2,3,4-tetrahydro-2-silanaphthalene and triphenylallylgermane have been studied in carbon tetrachloride, acetic acid and methanol as solvents. Either cleavage of the M-allyl bond (M = Si, Ge) or addition on the double bond (M = Si) takes place according to the nucleophilicity of the solvent. Cleavage of the M-carbon bond has also been studied with Ph 3 SiCH 2 CH 2 Cl and Ph 3 GeCH 2 CH 2 Cl. The nucleophilicity of the solvent and steric effects are main factors controlling these reactions. Mechanisms are advanced for each reaction.

New phosphonates containing a π-conjugated ferrocenyl unit

A new class of phosphorus compounds containing a ferrocenyl unit are obtained from vinylferrocene and phosphono-substituted aromatic halides by using palladium-catalyzed Heck-type reactions. The crystal structure of compound 3a confirms the trans planar geometry of the π-conjugated system. The electrochemistry and electronic absorption spectra of phosphorus esters 3a,b and acids 4a,b are investigated.

Coordination chemistry of group 14 metalloles: VI. Crystal structure and dynamic stereochemistry of cis-dicarbonyl-bis(φ4-1,1,3,4-tetramethylsilole)molybdenum and related complexes

Abstract The crystal structure of cis-Mo(CO)2(η4-1,1,3,4-tetramethylsilole)2 (1) shows the presence of only the uu isomer, as an enantiomeric pair (Δ, Λ). Variable temperature NMR measurements reveal the presence in solution of the Δ and Λ enantiomers (presumably uu) for the four cis-MT(CO)2(η4-silole)2 complexes, MT  Mo (1, 6), MT  W (2) and cis-Mo(CO)2(η4-germole)2 (3), but also the diastereoisomers (ΔΛ uu and trans ou) in the case of cis-Mo(CO)(PPh3)(η4-silole)2 (5). IR spectroscopy confirms the presence of diastereoisomers for all the complexes and 31P NMR also shows this in the case of 5. The structures of the diastereoisomers are assigned on the basis of the multiplicity of the 1H NMR signals. Both rotations of the η4 ligands and classical twists, of the type usually associated with octahedral chelate complexes, are necessary to explain this dynamic behaviour fully. The activation parameters have been calculated and the values of 30–40 kJ mol−1 for ΔG* at the coalescence temperature are comparable to those obtained for similar systems.

Coordination chemistry of siloles: reaction of η4-complexed endo-1-chloro-2,5-diphenylsilacyclopentadiene with lithium reagents. Synthesis of new carbenes, and the crystal structure of dicarbonylphenyl(η4-exo-1-methyl-1-oxy-2,5-diphenylsilacyclopentadiene)carbene iron

Abstract The reaction of MeLi, PhLi and i-Pr 2 NLi with (η 4 - endo -1-chloro- exo -1-methyl-2,5-diphenylsilacyclopentadiene)tricarbonyliron ( 1 ) has given a neutral carbene with an unusual cyclic structure. An X-ray structure determination was carried out in the case of the product, 4b , from PhLi.