Rhenium and Ruthenium-Catalyzed Processes Involving Organosilanes

Abstract

The hydrosilylation reaction between silanes and various carbonyl substrates such as aldehyde, ketone, ester, and carbonate has been catalyzed by Re(CO)5Cl UV photolysis. The IR spectrum of the rhenium carbonyl dimer HRe2(CO)9(SiR3) has been recorded in the reaction mixture. This complex is believed to be the resting state of the active catalyst Re(CO)4SiR3, which could be released upon photactivation. A catalytic mechanism involving this species has been proposed and shown to be thermodynamically feasible using computational studies. Ru3(CO)12 has been shown to catalyze the coupling of silanes with thiols, alcohols and amines with turnover number (TON) and turnover frequency (TOF) of up to 200 and 50 hr-1 at 80?C. IR, NMR and mass spectroscopic studies have identified a ruthenium dimer complex, [Ru(CO)4(SiEt3)]2 as a likely resting state of the catalyst. A mechanism involving this complex has been proposed for the silicon-thiol coupling process.