Abstract
Preparations are described for some new and known complex hydrides, trans-[(RR'R1''P)[2]PtHxJ], where R, R', R" are alkyl and aryl groups, and X is a halide or pseudo-halide ligand. Mechanisms are proposed for the preparative reactions. Infrared spectroscopic data are presented for the compounds. Variation of the solid state spectra with the method of preparation is explained, and assignments of platinum-hydrogen stretching absorptions are made. Trans-influence values of the ligands X are defined in terms of platinum-hydrogen stretching frequencies (Pt-H), and their dependence on the cis-ligands and the solvent or phase is described. The nature and site of solvation in the complex molecule is deduced from infrared solution studies. Trans-influences are related to the electronegativity and ligand-platinum (6psigma) overlaps of X. Proton magnetic resonance spectroscopic data are also given. Variations of the hydridic proton chemical shifts (tau[H]), platinum-hydrogen coupling constants (J[Pt-H]), and phosphorus-hydrogen coupling constants (J[P-Pt-H]) with both. X and R are rationalised on the basis of current theories. Approximate correlations between tau[H] and Pt-H and also J[Pt-H] and the ligand field strength of X are discussed. When X is isocyanate, isothiocyanate and cyanide, temperature and phosphine-dependent broadening of the hydridic resonances is observed. This is ascribed to intermolecular exchange of the tertiary phosphine ligands, and a mechanism for the interchange is suggested. The thiocyanatohydrides show linkage isomerism, and spectroscopic parameters are assigned to both the N- and S-bonded isomers. Isomer ratios are calculated for pure liquids and solutions, and solvent effects on the ratio are demonstrated. The complexes trans-hydrido(trichlorotin)bis(tri-n-butylphosphine)-platinum(II) and trans-hydrido(tribromotin)bis(tri-n-butylphosphine)-platinum(II) are shown by Raman spectroscopy to contain metal-metal bonds. The trans-influences of the trichlorotin(II) and tribromotin(II) ligands are determined.