Efficient Cobalt-Catalyzed Coupling of Amines and Siloxanes to Prepare Ceramics and Polymers

The phosphine-substituted aryl diimine cobalt catalyst,((Ph2PPr)ADI)Co, has been found to mediate the dehydrocouplingof diaminesor polyamines to poly(methylhydrosiloxane) (PMHS) to generate hydrogenand crosslinked solids in an atom-efficient fashion. The resultingsiloxane diamine and siloxane polyamine networks persist in the presenceof air or water at room temperature and can tolerate temperaturesof up to 1600 & DEG;C. Upon lowering the catalyst loading to 0.01mol %, ((Ph2PPr)ADI)Co was found to catalyze the dehydrocouplingof 1,3-propanediamine and PMHS (m = 35) to generatea siloxane diamine foam with a turnover frequency of 157 s(-1) relative to diamine consumption, the highest activity ever reportedfor Si-N dehydrocoupling. Furthermore, upon systematicallyreducing the number of potential branch points, the ((Ph2PPr)ADI)Co-catalyzed dehydrocoupling of diamines with hydride-terminatedpoly(dimethylsiloxane) (PDMS) was found to yield linear siloxane diaminepolymers with molecular weights of up to 47,300 g/mol. The dehydrocoupling of diamines and polyaminesto hydride-functionalizedsiloxanes has been achieved with substrate utilization turnover frequenciesof up to 157 s(-1) at ambient temperature.