Isomeric hydrido/vinylidene, MH(halide)(C=CH<sub>2</sub>)L<sub>2</sub>, and ethylidyne, M(halide)(C-CH<sub>3</sub>)L<sub>2</sub> (M = Os, Ru; L equals phosphine), are energetically similar but not interconverting - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Organometallics Année : 1998

Isomeric hydrido/vinylidene, MH(halide)(C=CH2)L2, and ethylidyne, M(halide)(C-CH3)L2 (M = Os, Ru; L equals phosphine), are energetically similar but not interconverting

Résumé

It is shown that there is no deuterium-isotope incorporation in the vinylidene CHPh group of RuDX(CCHPh)((PBu2Me)-Bu-t)(2) (X = Cl, I) on the time scale of 24 h at 25 degrees C, which indicates that the (unobserved) isomeric alkylidyne species RuX(CCHDPh)((PBu2Me)-Bu-t)(2) is not readily accessible under these conditions. Ab initio (B3LYP) calculations on the model MHCl(CCH2)(PH3)(2) (M = OS, Ru) show the ethylidyne isomer MCl(CCH3)(PH3)(2) to be close in energy (2.5, -1.1 kcal mol(-1) for Os and Ru, respectively) and effectively inaccessible at 25 degrees C due to the high energy (54.2, 45.5 kcal mol(-1) for Os and Ru, respectively) of the transition state for such a 1,3-migration. In contrast, simple rotation of the CCH2 group of MHCl(CCH2)(PH3)(2) by 180 degrees around the C-C axis is calculated to have a low barrier (8.1, 4.3 kcal mol(-1) for Os and Ru, respectively), indicating this to be the mechanism for isomerization observed in OsHCl(CCHPh)((PPr3)-Pr-i)(2).

Dates et versions

hal-00429122 , version 1 (30-10-2009)

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Citer

Montserrat Oliván, Eric Clot, Kenneth G. Caulton, Odile Eisenstein. Isomeric hydrido/vinylidene, MH(halide)(C=CH2)L2, and ethylidyne, M(halide)(C-CH3)L2 (M = Os, Ru; L equals phosphine), are energetically similar but not interconverting. Organometallics, 1998, 17, pp.897-901. ⟨10.1021/om9709493⟩. ⟨hal-00429122⟩
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