Nickel-Catalyzed Double Silylation of a Variety of Carbonyl Compounds with 1,2-Bis(dimethylsilyl)carborane

The nickel-catalyzed reactions of 1,2-bis(dimethylsilyl)carborane 1 with aldehydes such as isobutyraldehyde, trimethylacetaldehyde, hexanal, and benzaldehyde afforded 5,6-carboranylene-2-oxa-1,4-disilacyclohexanes. The dehydrogenative 1,4-double silylation of methacrolein and trans-4-phenyl-3-buten-2-one in the presence of a catalytic amount of Ni(PEt3)4 took place under similar conditions. In contrast, the reaction of 1 with α-methyl-trans-cinnamaldehyde and trans-cinnamaldehyde under the same reaction conditions yielded the insertion compounds formed via insertion of a carbonyl group into each of the C−Si bonds of 1. The reaction of 1 with diphenylketene gave the 1,2-adduct across the carbonyl group. The structures of compounds 8, 11, and 14 were determined by single-crystal X-ray crystallography.