ACTIVATION OF A CARBON-CARBON BOND IN SOLUTION BY TRANSITION-METAL INSERTION

CLEAVAGE of carbon-carbon bonds by transition-metal-containing heterogeneous catalysts forms the basis of one of the most important industrial processes, the refining of petroleum to chemicals and fuels1. But the generally low product selectivity observed with heterogeneous systems is a significant drawback. For this reason, much effort has been devoted to developing transition-metal complexes that can be inserted into C-C bonds in homogeneous media, as such catalysts can operate under mild, easily controlled conditions and might offer high selectivity and reactivity. Metal insertion into C-H bonds is well known2,3-5, but, except in a few special cases2,6-12, C-C bonds are generally unreactive towards insertion of transition metals in solution. Here we report the selective activation of a simple C-C bond by a mononuclear rhodium complex in a neutral homogeneous medium (tetrahydrofuran solution). We are able to effect Rh insertion into a C-C bond in a diphosphinoxylene, in which this bond is favourably oriented towards the transition-metal centre. The competing reaction of insertion into C-H is suppressed by the use of an overpressure of H-2. We suggest that this approach might lead to a general strategy for C-C activation in homogeneous systems.