Ditertiary phosphine complexes of nickel. Spectral, magnetic, and proton resonance studies. A planar-tetrahedral equilibrium

Article abstract of DOI:10.1021/ic50045a029

A number of complexes of nickel in oxidation states 0, II, and III with the ditertiary phosphines (C₆H₅)₂P(CH₂)_nP(C ₆H₅)₂ (n = 1, 2, or 3) are reported and studied by spectral and magnetic methods. In solution in organic solvents complexes of the type Ni[(C₆H₅)₂P(CH₂)_nP(C ₆H₅)₂]X₂ where X = Br or I and n = 2 remain diamagnetic. The analogous complexes with n = 3 show a square-planar (diamagnetic)-tetrahedral (paramagnetic) equilibrium in solution. Isotropic proton magnetic resonance shifts were observed in these systems and thermodynamic parameters for the equilibrium were obtained from the temperature dependences of these shifts. The epr spectrum of polycrystalline Ni[(C₆H₅)₂P(CH₂)₃P(C ₆H₅)₂]Br₃ shows an isotropic signal at g = 2.218.