98651-98-0Relevant articles and documents
Four- and five-coordinate platinum complexes of divinylphenylphosphine
Holt, Mark S.,Nelson, John H.,Alcock, Nathaniel W.
, p. 2288 - 2295 (2008/10/08)
A series of platinum(II) complexes of the type L2PtX2 (L = divinylphenylphosphine; X = Cl, Br, I) have been prepared and characterized by elemental analyses, physical properties, conductance measurements, infrared spectroscopy, and 1H, 1H{31P}, 13C{1H}, 13C{1H,31P}, 31P{1H} and 195Pt{1H} NMR spectroscopy. All complexes are nonelectrolytes, and most possess the cis geometry in solution as well as in the solid state. However, L2PtI2 slowly isomerizes from cis to trans in CDCl3 solution. Variable-temperature 31P{1H} NMR spectroscopy and conductance studies of the equilibrium L2PtX2 + L ? L3PtX2 have been analyzed in terms of intra- and intermolecular equilibria of the pentacoordinate species L3PtX2. The formation of L3PtX2 is enthalpy-driven. The crystal structures of dichlorobis(1-phenyl-3,4-dimethylphosphole)platinum(II) (1) and dichlorobis(divinylphenylphosphine)platinum(II) (2) have been determined from three-dimensional X-ray data collected by counter methods. Compound 1 crystallizes in space group P21/c with a = 11.285 (2) ?, b = 11.269 (2) ?, c = 19.386 (3) ?, β = 92.36 (1)°, and Z = 4. Compound 2 crystallizes in space group P1, with a = 7.861 (2) ?, b = 16.783 (5) ?, c = 8.804 (3) ?, α = 107.59 (2)°, β = 94.93 (2)°, γ = 101.56 (2)°, and Z = 2. Both structures were refined by least-squares methods with R = 0.028 for 1 and R = 0.033 for 2 for 3327 and 3446 reflections with I/σ(I) > 3.0 for 1 and 2, respectively. The molecular structures are remarkably similar to one another and contain cis-four-coordinate platinum(II) with no unusual bond distances or internuclear contacts. Detailed comparisons of these structures together with the solution NMR data for the L3PtX2 complexes suggest that steric rather than electronic factors are dominant in determining the thermodynamic stability of the pentacoordinate complexes. These conclusions are strengthened by analysis of the infrared data in the CO stretching region for the complexes LMo(CO)5 (L = divinylphenylphosphine, 1-phenyl-3,4-dimethylphosphole). Cotton-Kraihanzel force field analyses and Graham σ- and π-bonding parameters suggest that the phosphole is both a better σ-donor and π-acceptor than the phosphine toward Mo(0). All the data for the platinum complexes suggest that toward Pt(II) these two ligands have similar donor abilities.
