Search results for "Methyllithium"
showing 5 items of 5 documents
A reinvestigation of compound CpMo(PMe3)2(CH3)2: Alkylation by single electron transfer and radical addition?
2001
International audience; The synthesis of the half-sandwich molybdenum(III) diphosphine dimethyl complex CpMo(PMe3)2(CH3)2 has been reinvestigated. The compound was obtained from the corresponding dichloro complex CpMo(PMe3)2Cl2 and methyllithium at low temperatures and isolated as a crystalline product by conducting all operations at temperatures lower than −10 °C. The complex is thermally unstable at room temperature but has been fully characterised by EPR spectroscopy, cyclic voltammetry and X-ray diffraction. The formation reaction is retarded by excess phosphine. On the basis of this and other related observations, a mechanism involving phosphine pre-dissociation followed by single elec…
Cyclopentadienylmolybdenum(II) and -(III) complexes containing diene and allyl ligands. Part 4. Reactivity studies of the bisallyl complex CpMo(supin…
1998
Abstract Compound CpMo( η 3 -C 3 H 5 ) 2 , 3, has been synthesized from CpMoCl 4 and four equivalents of allylmagnesium bromide. While the compound is stable in donor solvents at room temperature, warming in refluxing MeCN induces the formation of 1,5-hexadiene by a metal-mediated allyl-allyl coupling process. Treatment of 3 with Bu t NC at room temperature affords CpMo( η 3 -C 3 H 5 )(Bu t NC) 2 , 4. A similar reduction with presumed allyl radical loss occurs for [CpMo( η 3 -C 3 H 5 )( η 4 -C 4 H 6 )] + , [1c] + , to afford [CpMo( η 4 -C 4 H 6 )(Bu t NC) 2 ] + , 5. Treatment of [1c] + with methyllithium affords two products, the major one (1c) corresponding to the one-electron reduction pa…
Dialkyl titanium complexes that contain a sulfur-linked bis(phenolato) ligand:
2002
Abstract The sulfur-linked bis(phenol) 2,2′-thiobis(2-tert-butyl-4-methylphenol), tbmpH2, reacted cleanly with titanium tetrachloride to give the orange titanium dichloro complex [Ti(tbmp)Cl2]2 in virtually quantitative yield. Reaction of the dichloro complex [Ti(tbmp)Cl2]2 with methyllithium at low temperature gave the unexpectedly thermally robust, yellow dimethyl complex [Ti(tbmp)Me2]. The reaction of the dichloro complex with benzyl Grignard reagent in pentane afforded the highly crystalline dibenzyl complex [Ti(tbmp)(CH2Ph)2] as a 1,4-dioxane adduct. The single crystal X-ray crystallography revealed a centrosymmetric 1,4-dioxane-bridged molecule that contains two fragments containing s…
Substituted 1,4-Diaza-1,3-butadiene Monocyclopentadienyl Titanium Complexes. Crystal Structure of Ti(η5-C5Me5)(η4-iPrNCHCHNiPr)Me
2000
We report the synthesis of 1,4-diaza-1,3-butadiene (dad) complexes Ti(η5-C5R5)(η4-R‘2-dad)Cl (R = H, Me; R‘ = iPr, tBu) by reaction of Ti(η5-C5R5)Cl3 (R = H, Me) with the dilithium salts of diisopropyl- and di-tert-butyl-substituted 1,4-diaza-1,3-butadienes (Li2[R‘2-dad]). Alkylation of the pentamethylcyclopentadienyl diisopropyl and di-tert-butyl derivatives with methylmagnesium chloride and methyllithium gave complexes Ti(η5-C5Me5)(η4-iPr2-dad)Me and Ti(η5-C5Me5)(η4-tBu2-dad)Me, respectively. Addition of excess water to di-tert-butyl chloro complexes gave the oxo-bridged complexes [{Ti(η5-C5R5)(η4-tBu2-dad)}2(μ-O)] (R = H, Me). The temperature-dependent spectroscopic behavior of Ti(η5-C5H…
Stereoselectivity in the Addition of Organotitanium Reagents to Carbonyl Compounds
1986
Although great strides have been made in the area of stereoselective C—C bond forming reactions [1], many problems persist. Early studies concerning chemo- selective reactions of organotitanium reagents (Chapter 3) suggested that they might also behave stereoselectively in relevant cases. In fact, the first such observation goes back to 1979 when it was noted that dichlorodi- methyltitanium (2) adds to the ketone 1 in CH2C12 to produce a mixture of tertiary alcohols 4/5 instead of the desired (±) cuparene (3) [2, 3]. The striking aspect of this transformation is the high disastereoselectivity in favor of 4. Methyllithium shows the opposite stereoselectivity (4:5 = 34:66), in line with the s…