Synthesis, Structure, and Reactivity of [{Ir(cod)(μ-OSiMe3)}2] with Styrene and Vinylsilanes: Catalytic Activation of the Vinylic C−H Bond

This paper reports the first successful synthesis of iridium-siloxide complex [{Ir(cod)(μ-OSiMe 3 )} 2 ] ( I ), whose structure has been determined by X-ray diffraction. Complex I has an A-frame bis-square planar geometry and is a selective catalyst of silylative heterocoupling of styrene with vinyltrisubstituted silanes CH 2 CHSiR 3 ( A ) (where R 3 = Me 3, Me 2 Ph, (OEt) 3 ), Me 2 (OSiMe 3 ), Me(OSiMe 3 ) 2 ) and/or of hydrovinylation (co-dimerization) of styrene with vinylsilanes CH 2 CHSi(OR‘) 3 ( B ) (where R‘ = SiMe 3, tert -Bu). Results of a stoichiometric study of I with substrates and labeling experiments (GC−MS and 1 H NMR analysis) with the deuterated styrene indicate the exchange of the vinylic proton and a non-metallacarbene mechanism of the two reactions proceeding via generation of active Ir−H intermediates by oxidative addition of C−H to monomeric iridium-siloxide complexes. All the data allowed us to propose a reasonable mechanism of the silylative coupling, which does not involve migratory insertion of olefin into the Ir−Si bond as well as a mechanism of the hydrovinylation (co-dimerization) of styrene with vinyltris(trimethylsiloxy)silane.