CO and CO/H Conversion to Methoxide by a Uranium(IV) Hydride.

Here we show that a scaffold combining siloxide ligands and a bridging oxide allows the synthesis and characterization of the stable dinuclear uranium(IV) hydride complex [K{[U(OSi(O Bu))](μ-O)(μ-H)}], 2, which displays high reductive reactivity. The dinuclear bis-hydride 2 effects the reductive coupling of acetonitrile by hydride transfer to yield [K{[U(OSi(O Bu))](μ-O)(μ-κ-NC(CH)NCHCH)}], 3. Under ambient conditions, the reaction of 2 with CO affords the oxomethylene reduction product [K{[U(OSi(O Bu))](μ-CHO)(μ-O)}], 4, that can further add H to afford the methoxide hydride complex [K{[U(OSi(O Bu))](μ-OCH)(μ-O)(μ-H)}], 5, from which methanol is released in water. Complex 2 also effects the direct reduction of CO to the methoxide complex 5, which is unprecedented in f element chemistry. From the reaction of 2 with excess CO, crystals of the bis-formate carbonate complex [K{[U(OSi(O Bu))](μ-CO)(μ-HCOO)}], 6, could also be isolated. All the reaction products were characterized by X-ray crystallography and NMR spectroscopy.