Heterogeneous catalysts based on supported Rh-NHC complexes: synthesis of high molecular weight poly(silyl ether)s by catalytic hydrosilylation

The new rhodium( i ) complexes [Rh(Cl)(COD)(R-NHC-(CH 2 ) 3 Si(O i Pr 3 ) 3 )] (R = 2,6-diisopropylphenyl ( 2a ); n -butyl ( 2b )) have been synthesised and fully characterised. The study of their application as ketone hydrosilylation catalysts showed a clear N-substituent effect, 2a being the most active catalyst precursor. Complex 2a has been immobilised in the mesoporous materials MCM-41 and KIT-6. The new hybrid materials have been fully characterised and used as catalyst precursors for the preparation of poly(silyl ether)s by catalytic hydrosilylation. The heterogeneous catalytic systems based on the materials 2a -MCM-41 and 2a -KIT-6 afford polymers with high average molecular weight ( M w ) M w = 2.61 × 10 6 g mol −1 ( 2a -MCM-41) and M w = 4.43 × 10 5 g mol −1 ( 2a -KIT-6). Poly(silyl ether)s with a high average M w (2.6 × 10 6 g mol −1 ) were obtained by rhodium-catalyzed hydrosilylation.