Manganese catalysed dehydrocoupling of silanes and siloxanes with ammonia to prepare oligosilazanes and polysiloxazanes†
Abstract
The halogen-free synthesis of oligosilazanes has been observed upon dehydrocoupling silanes with ammonia at 25 °C using [(2,6-iPr2PhBDI)Mn(μ-H)]2. Extending this methodology to polymethylhydrosiloxanes afforded thermally robust polysiloxazane solids, and the dehydrocoupling of 1,3,5,7-tetramethylcyclotetrasiloxane with ammonia afforded a polysiloxazane having a weight-average molecular weight of 4300 g mol−1. A representative oligosilazane has been applied to a copper surface and found to afford a 20 μm thick coating that resists corrosion after 24 h under water. Addition of ammonia to [(2,6-iPr2PhBDI)Mn(μ-H)]2 allowed for characterization of the catalyst resting state, [(2,6-iPr2PhBDI)Mn(μ-NH2)]2, which has been found to mediate Si–N dehydrocoupling.