Metal Carbonyl Catalysts for the Transformation of Silicon Hydrides to Siloxanes in the Presence of DMF

The reduction of carbonyl systems using organosilanes is a well known methodology that works efficiently with transition metal complexes. However, to date, no process involving possible organosilicon intermediates and metal catalytic transients has been reported to back up a general mechanism. It has recently been reported that, upon photochemical irradiation, tertiary silanes (R₃SiH) react with DMF to form disiloxanes (R₃Si-O-SiR₃) and Me₃N using the transition metal alkyl complex (η₅-C₅H₅)Fe(CO)₂Me as a catalyst. Intermediates of the type R₃SiOCH₂NMe₂ were proposed as the important first step via a hydrosilylation reaction but no evidence was obtained for this suggestion. By changing the catalyst to M(CO)₆ (M=Cr, Mo, W) the steric effect was reduced making possible to observe not only the expected disiloxanes, but for the first time the presence of the suggested intermediates. We have synthesized such intermediates via an independent method and proved that they can indeed further react with R₃SiH to form the disiloxane products.