Chelate and Pincer Carbene Complexes of Rhodium and Platinum Derived from Hexaphenylcarbodiphosphorane, Ph₃PCPPh₃

The reaction of [(cod)RhCl]2 with Ph3PCPPh3 (1) gave the bidentate Rh(I) carbene complex, (cod)Rh[η2-C{P(C6H4)Ph2}{PPh3}] (2), in which one of the Ph groups in 1 underwent orthometalation to form the chelate. Displacement of cod by 2 equiv of PMe3 transformed 2, via a second orthometalation event, into the Rh(III) C,C,C pincer carbene complex, HRh(PMe3)2[η3-C{P(C6H4)Ph2}2] (3). The reaction of [Me2Pt(SMe2)]2 with 1 led directly to the analogous C,C,C pincer carbene complex of Pt(II), (Me2S)Pt[η3-C{P(C6H4)Ph2}2] (4). DFT calculations on a model form of 3 suggest a net single σ-bonding interaction between Rh and an sp2-hybridized carbene center, with a HOMO that is predominantly carbene pz in character.