Metal-metal bonded homo- and heterobimetallic compounds of Pt(I) and Pd(I) supported by a bridging-N,P : N ’,P ’ moiety of a potentially hexadentate ligand

Reactions of metal-metal bonded homobimetallic (Pd-2) and heterobimetallic (PtPd) complexes, supported by a P,P’-bridging-bis(P,N-chelating) coordination mode of the potentially hexadentate ligand 1,1-bis[di(o-N,N-dimethylanilinyl)phosphino]methane (dmapm), with CO, diethylacetylenedicarboxylate (DEAD), and thiols (FISH) in CH2Cl2 are described. At room temperature, rac-Pd2Cl2(mu-N,P:P’,N’-dmapm) gives the stable complexes Pd2Cl2(mu-CO)(2)-(mu-P:P’-dmapm) and PdCl(eta(2)-DEAD)(mu-P:P’, N-dmapm)PdCl (which is fluxional in solution), while rac-PtPdCl2(mu-N,P:P’, N’-dmapm) disproportionates to PtCl2(P,P’-dmapm) and Pd metal, although at low temperature intermediate carbonyl species are detected in the CO reaction. The reactions with thiols in the presence of triflic acid (HOTf) generate rac-[MPdCl2(mu-SR)(mu-N,P:P’,N’-dmapm)][OTf] and H-2 for both M = Pt and Pd. In CH2Cl2, PdX2(dmapm) species (X = halide or CN) exist as equilibrium mixtures of P,P’ and P,N-ligated forms. For X = Cl, the P,P’-PN equilibrium is governed by DeltaHdegrees = -5.5 +/- 0.5 kJ mol(-1) and DeltaSdegrees = 10 +/- 1 J mol(-1) K-1, and the ring-strain energy within the P,P’-isomer is similar to32 kJ mol(-1); the equilibrium increasingly favors the P,N-form with X = CN much greater than I > Br > Cl. The solid-state structures of rac-[PtPdCl2(mu-SEt)(mu-NP:P’,N’-dmapm)][OTf] and PdCl2(P,N-dmapm) are presented; the latter contains both bound and free N- and P-atoms of identical types in the same molecule and permits an assessment of sigma- and pi-bonding between these atoms and Pd.