Catalytic Oxidation of Binap on (Binap)Rh(Co)ci

The square planar complex, (BINAP)Rh(CO)Cl (BINAP 2,2’-bis(diphenylphosphino)-1,1’-binapthyl) was synthesised from [Rh(COD)Cl]2 (COD = 1,5 cyclooctadiene) and BINAP under a CO atmosphere. This complex reacts with oxygen to form the square-planar complex (BINAP(O))Rh(CO)Cl in approximately 50% yield, along with free BINAP dioxide (BINAP(O)2). The evolution of CO2 gas and the formation of other unidentified products were also detected. In the presence of excess BINAP under CO/O2 gas mixtures, the reaction is catalytic with a TOF of 0.16 h-1 at ambient temperature. The kinetics of this transformation were investigated and a mechanism is proposed. To the best of our knowledge, this chemistry represents the first example of a reaction exhibiting oxidation of both phosphorus atoms on the BINAP ligand and concurrent oxidation of one phosphorus atom and the CO ligand in the same complex.