Breaking C–O Bonds with Uranium: Uranyl Complexes as Selective Catalysts in the Hydrosilylation of Aldehydes

We report herein the possibility
to perform the hydrosilylation
of carbonyls using actinide complexes as catalysts. While complexes
of the uranyl ion [UO2]2+ have been poorly considered
in catalysis, we show the potentialities of the Lewis acid [UO2(OTf)2] (1) in the catalytic hydrosilylation
of a series of aldehydes. [UO2(OTf)2] proved
to be a very active catalyst affording distinct reduction products
depending on the nature of the reductant. With Et3SiH,
a number of aliphatic and aromatic aldehydes are reduced into symmetric
ethers, while iPr3SiH yielded
silylated alcohols. Studies of the reaction mechanism led to the isolation
of aldehyde/uranyl complexes, [UO2(OTf)2(4-Me2N-PhCHO)3], [UO2(μ-κ2-OTf)2(PhCHO)]n, and
[UO2(μ-κ2-OTf)­(κ1-OTf)­(PhCHO)2]2, which have been fully characterized
by NMR, IR, and single-crystal X-ray diffraction.