STUDIES ON MIXED LIGAND COMPLEXES, PART II. COBALT(III) HETEROCHELATES CONTAINING NONPLANAR QUADRIDENTATE LIGANDS

Abstract

A series of new cobalt (III) mixed ligand complexes of the type [Co(AA) (BBBB)] [where AA = bidentate monobasic NO or OO donor ligands such as picolinic acid, quinaldinic acid, acetylacetone, tropolone, acetoacetanilide, N-benzoylphenyl-hydroxylamine, benzohydroxamic acid, and BBBB = quadridentate ONNO donor ligand like N,N′-trimethylenediaminebis (salicylideneimne)(saltnH₂)] were synthesized and characterized by elemental analysis, conductance measurements, electronic spectra, infrared spectra, molecular weight and magnetic susceptibility measurements. The complexes are green in color, monomers, non-electrolytes and diamagnetic. In these heterochelates the quadridentate ligand saltn adopts an unusual nonplanar twisted conformation and the bidentate ligand occupies two cis positions. The magnetic and electronic spectral data of the complexes indicate distorted octahedral structure of the complexes. Electronic spectral data in non-coordinating and coordinating solvents indicate that the heterochelates with saltn are stable to pyridine attack which is contrary to the electronic spectra of similar heterochelates with salen [where salenH₂ = N,N′-ethylenediaminebis (salicylideneimine)]. The latter heterochelates undergo rearrangement in pyridine and two molecules of pyridine enter the coordination zone with simultaneous removal of the bidentate ligand.