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.