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

CLEAVAGE of carbon-carbon bonds by transition-metal-containing heterog eneous catalysts forms the basis of one of the most important industri al processes, the refining of petroleum to chemicals and fuels1. But t he generally low product selectivity observed with heterogeneous syste ms is a significant drawback. For this reason, much effort has been de voted to developing transition-metal complexes that can be inserted in to C-C bonds in homogeneous media, as such catalysts can operate under mild, easily controlled conditions and might offer high selectivity a nd 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 unreacti ve 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). W e are able to effect Rh insertion into a C-C bond in a diphosphinoxyle ne, in which this bond is favourably oriented towards the transition-m etal centre. The competing reaction of insertion into C-H is suppresse d 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 sys tems.