Synthesis and Characterization of Heterobimetallic Complexes Derived from (o-(Diphenylphosphino)benzoyl)pinacolone (HacacP). The Structure of PtCl2

Article abstract of DOI:10.1021/ja00331a014

The synthesis and characterization of heterobimetallic complexes of (o-(diphenylphosphino)benzoyl)pinacolone are described.Reaction of 2 equiv of HacacP with MCl2(COD) (M=Pd, Pt), Rh2Cl2(CO)4, and IrCl(CO)2(p-H2NC6H4CH3) gave the metallo ligands of formulas ML2(HacacP)2 where ML2=cis-PdCl2 and PtCl2 and trans-Rh(CO)Cl and Ir(CO)Cl.The ML2(HacacP)2 metallo ligands undergo smooth metalation by cupric carboxylates giving the heterobimetallic complexes of the formula ML2.The diamagnetic heterobimetallic complex PtCl2 was prepared from TiCl4 and PtCl2(HacacP)2.On the basis of 31P NMR, the Pt-Ti complex contains an unsymmetrical cis-TiCl2(acacP)2 subunit attached to a cis-PtCl2 moiety.Treatment of ZnEt2 with 2 equiv of HacacP followed by IrCl(CO)2(p-H2NC6H4CH3) gave trans-IrCl(CO).The low-temperature 31P NMR spectrum of the Ir-Zn complex established the predominance of an isomer featuring trans but nonequivalent phosphines.By IR spectroscopy, the Ir-Zn and Ir-Cu complexes are structurally similar as are the Pd-Cu and Pt-Cu compounds.The Pt-Cu complex was characterized by single-crystal X-ray crystallography.PtCl2*2CH2Cl2*H2O crystallizes in the centrosymmetric triclinic space group P1-C¹_i (no. 2) with a=11.914(6) Angstroem, b=11.646(6) Angstroem, c=21.125(10) Angstroem, α=102.34(4) deg, β=103.71(4) deg, γ=99.83 deg, and Z=2.The empirically weighted full-matrix least-squares refinement converged to R₁=0.053 and R₂=0.065 for 8881 independent reflections having 2θ(Mo Kα)<55 deg and I>3?(I).The molecule consists of square-planar PtCl2P2 and Cu(β-diketonate)2 subunit with a nonbonding Pt...Cu separation of 3.97 Angstroem.Optical spectra of IrCl(CO) exhibit an intense absorption at 960 nm that is not found in typical square-planar Ir(I) or Cu(II) model compounds.This band disappears upon treatment with SO2, and the visible spectrum of IrCl(CO)*SO2 resembles that for a typical Cu(β-diketonate)2 chromophore.Similarly EPR studies indicate that the Pt-Cu and Ir-Cu-SO2 complexes consist of axially symmetric Cu moiety.EPR studies on IrCl(CO) indicate that it contains a low-symmetry Cu site (g_x=2.038, 2.146, 2.278) and a relatively small isotropic hyperfine splitting, both of which are consistent with the presence of a tetrahedrally distorted Cu(β-diketonate)2 unit.These data are consistent with the formation of an enolate bridge between iridium and copper centers.