Institution: | a URA 322, Chimie, Electrochimie Moléculaires et Chimie Analytique, Université de Bretagne Occidentale, 6 Avenue Le Gorgeu, BP 809, 29285, Brest Cedex, France b URA 1495, Chimie du Solide et Inorganique Moléculaire, Université de Rennes I, Avenue du Général Leclerc, 35042, Rennes Cedex, France |
Abstract: | The reactivity, towards nucleophiles and electrophiles, of dimolybdenum allenylidene complexes of the type Cp2Mo2(CO)4(μ,η2(4e)-C=C=CR1R2)] (Cp=η5-C5H5) has been investigated. The nucleophilic attacks occur at the Cγ carbon atom, while electrophiles affec the C atom. Variable temperature solution 1H NMR studies show a dynamic behavior of these complexes consisting of an equilibrium between two enantiomers with a symmetrical Cp2Mo2(CO)4(μ-σ,σ(2e)-C=C=CR1R2)] transition state. Extended Hückel MO calculations have been carried out on the model Cp2Mo2(CO)4(μ,η2-C=C=CH2]. The calculated charges of the allenylidene carbon atoms suggest that the electrophilic attacks are under charge control, while the nucleophilic attacks are rather under orbital control. |