Transition metal chemistry of quinuclidinone-containing ligands. II. Spectral and megnetic properties of some transition metal complexes containing 2(N-morpholinylmethyl)-3-quinuclidinone and related ligands

Abstract

Complexes of cobalt(II), nickel(II), and iron(II) halides with the title compound were prepared by adding the appropriate metal salt to the ligand in alcoholic solutions. The complexes have pseudotetrahedral microsymmetry around the central metal ion as indicated by their spectral and magnetic properties; the coordination sphere contains one bidentate nitrogenbonded ligand and two halide atoms. Ligand field band assignments, metal-halide stretching frequencies, and magnetic susceptibility data are given for each of the complexes. The cobalt(II) and nickel(II) perchlorate complexes of the title compound were also prepared, and each contains two bidentate ligands which provide a tetrahedral ligand field that is stronger than for the halide complexes. It is suggested that the apparent preference of the ligand for one-to-one metal-toligand coordination and the consequent tetrahedral structures result from a combination of the size of the quinuclidine group and the rigidity of the five-membered chelate ring formed by the coordinated ligand. In addition to these pseudotetrahedral complexes, an octahedral nickel chloride complex which apparently contains bridging chloride ligands is reported. A cobaltous thiocyanate complex is also found to have an octahedral structure in the solid state and a tetrahedral structure in solution.(7) B.

Moessbauer, electronic, and structural properties of several bis- and tetrakis(pyridine)iron(II) complexes

“…The lower coordination number for a tetrahedral iron(II) complex leads to a lower isomer shift (0.70-0.90 mm/s) than in octahedral complexes. 58,59,61,63,84 The Mossbauer parameters presented in Table IV for Fe(py)2I2 provide further evidence for the pseudotetrahedral structure. The quadrupole interaction is typical of pseudotetrahedral iron(II) and indicates a splitting of the dx2_y2 and dz2 orbitals of the order of 100 cm-1 by the low-symmetry component of the ligand field.…”