Pseudotetrahedral cobalt(II) and nickel(II) zwitterion complexes

Abstract

The preparation and properties of cobalt(II) and nickel(II) complexes of the positively charged ligands, 2-(diphenylphosphinomethyl)-6-methylpyridinium ion (PN′H⁺) and 2-(β-diphenylphosphinoethyl)-6-methylpyridinium ion (PN″H⁺), are described. Magnetic measurements and i.r. and visible spectra show that all but one of the complexes have a pseudotetrahedral field about the metal ion, comprising one phosphorus atom and three halide ions, and that the protonated pyridine nitrogen is weakly hydrogen-bonded to a co-ordinated halide ion; the exception is the low-spin six-co-ordinate complex, Ni(PN″H)₂(NCS)₂(ClO₄)₂. The complexes undergo partial decomposition in solution.

The preparation of PN′H⁺ complexes from corresponding complexes of the neutral ligand, 2-methyl, 6-bis(diphenylphosphino)methylpyridine (PPN′)via a carbon–phosphorus bond fission reaction is also described.