Multimetallic Alkaline-Earth Hydride Cations

Reactions of dimeric beta-diketiminato (BDI) magnesium and calcium hydrides with [(BDI)Mg](+)[Al{OC(CF3)(3)}(4)](-) provide ionic multimetallic hydride derivatives, which have been characterized by single-crystal X-ray diffraction analysis. The exclusively magnesium centered species comprises a cation in which two [(BDI)Mg](+) units are connected by a single mu(2)-bridging hydride. In contrast, the greater lability of the calcium-containing system is underscored by the isolation of a cyclic heterotrimetallic species in which a CaH2 moiety is coordinated by a molecule of benzene and an aryl substituent of a [{(BDI)Mg}(2)H](+) cation. The homometallic dimagnesium species displays a greater facility toward reaction with diphenylacetylene than neutral [(BDI)MgH](2), although the resultant crystallographically characterized vinyldimagnesium cation equilibrates into a complex mixture of neutral and ionic species in solution. An initial assessment of both systems for the hydrosilylation of 1-hexene and diphenylacetylene evidences an inferior catalytic performance of [(BDI)MgH](2) in isolation.