Chemistry of Heterobifunctional Diazaphospholylphosphines. 4. Complexation and Reduction Reactions of Platinum(II) and Palladium(II) with Phosphine-Substituted (Fluoro, Dimethylamino, Trifluoroethoxy) 4-Phosphino-2,5-dimethyl-2H-1,2,3σ²-diazaphospholes. Structure of a Novel Platinum(0) Tetrakis(difluorophosphine) Complex

Abstract

Selected platinum(II) and palladium(II) complexes react with 4-(difluorophosphino)-2,5-dimethyl-2H-1,2,3σ2-diazaphosphole (LF) to form the expected X2M(LF)2 complexes. In some cases, redox processes yield stable, solid, M0(LF)4 complexes; thus Pd(cod)Cl2 with LF gave a mixture of the Pd0 and PdII complexes whereas Pt(cod)Cl2 gave only the Pt(LF)2Cl2 complex. With limited LF, (cod)Pt(Me)Cl gave the expected (LF)2Pt(Me)Cl complex, but when the reaction was carried out with excess LF, PtII was reduced to Pt0 to form the Pt0(LF)4 complex. This complex was structurally characterized. Crystal data for C16H28F8N8O2P8Pt: tetragonal, I4̄2m (No. 121), a = 11.961(2) Å, c = 15.034(3) Å, V = 2150.8(6) Å3, Z = 2. Final indices: GOF = 1.299 [F o 2 ≥ −3σ(F o 2)] and R 1 = 0.0381, wR 2 = 0.1180 (for F o 2 > 2σ(F o 2)) and R 1 = 0.0395, wR 2 = 0.1188 for all data. The structure around the Pt0 atom was revealed as a slightly squashed tetrahedron surrounded by four phospholylphosphine ligands coordinated through the exocyclic phosphine. The Pt−P distance is 2.237(3) Å. The Pd(LF)4 analogue was also isolated in pure form from the reaction of LF with Pd2(dba)3. The related 4-(bis(dimethylamino))-2,5-dimethyl-2H-1,2,3σ2-diazaphosphole (LN) displaced cod from M(cod)Cl2 (M = Pd, Pt) to give only the (LN)2MCl2 complexes (M = Pd and Pt) with no evidence for reduction of the metal center. The larger steric bulk of LN is presumably also the reason this ligand forms the trans complex instead of the cis complexes which were formed by LF from the same precursors in analogous reactions. The reaction of LN with (cod)Pt(Me)Cl produced only cis-(LN)2Pt(Me)Cl; there was no evidence of reduction to Pt0 in contrast to the behavior of LF. With LF, the stereochemistry of the final product was the same as that of the starting material. The third ligand, 4-(bis(trifluoroethoxy)phosphino)-2,5-dimethyl-2H-1,2,3σ2-diazaphosphole (LO) gave the expected platinum cis complex (LO)2MCl2 from the (cod)MCl2 precursor, but palladium rearranged during the complexation reaction to form the trans complex. Again, no evidence for reduction of either Pt or Pd was observed with LO.