Promoting the Hydrosilylation of Benzaldehyde by Using a Dicationic Antimony-Based Lewis Acid: Evidence for the Double Electrophilic Activation of the Carbonyl Substrate.

The concomitant activation of carbonyl substrates by two Lewis acids has been investigated by using [1,2-(Ph2 MeSb)2 C6 H4 ](2+) ([1](2+) ), an antimony-based bidentate Lewis acid obtained by methylation of the corresponding distibine. Unlike the simple stibonium cation [Ph3 MeSb](+) , dication [1](2+) efficiently catalyzes the hydrosilylation of benzaldehyde under mild conditions. The catalytic activity of this dication is correlated to its ability to doubly activate the carbonyl functionality of the organic substrate. This view is supported by the isolation of [1-μ2 -DMF][OTf]2 , an adduct, in which the DMF oxygen atom bridges the two antimony centers.