Spectroscopic Studies of Some Coordination Compounds

Abstract

In part one, spectroscopic methods are used in a study
of the products of some metal-promoted reactions of 2-cyanopyridine.
This compound reacts exothermically with copper(II)
chloride in methanol to give dichlorobis/ 0-methylpyridine-
-2-carboximidate /copper(II). Methyl 2-picolinate and
pyridine-2-carboxamide may both be obtained in good yield
via metal-promoted reactions of this type. Some proposed
mechanisms for these reactions are discussed. Nine new complexes
of O-methylpyridine-2-carboximidate are characterised
by spectroscopic, magnetic, and conductimetric methods,
Spectroscopic evidence for the electron-rich nature of this_
ligand is used in an explanation of its unusually high d-orbital
splitting capacity.

In part two, infrared and Raman data for triphenylamine,
tri(2-pyridyl)amine, tri(2-pyridyl)phosphine and tri(2-pyridylarsine)
are presented, and vibrational assignments are proposed.
A literature survey focuses attention on inter-ring
vibrational coupling in these molecules.

In part three, assignments for metal-ligand vibrations
in a closely related series of complexes of the type
bis/ tri(2-pyridyl)amine 7M *2x~ are made by comparing infrared
and Raman data obtained in both solid state and in solution.
Most of the "ligand" vibrations of the centrosymmetric cations
(Dag symmetry) are accidentally degenerate, but splittings
are observed in the low-spin complexes. Variable temperature
magnetic and spectroscopic studies of bis/ tri(2-pyridyl)-
amine /cobalt(II) perchlorate show that an equilibrium
between 4T and 2E spin states exists in this complex. The
dependence of the susceptibility on the crystal structure
in complexes of this type is attributed, in part, to variations
in the abilities of different lattices to accommodate the
predicted Jahn-Teller distortions in the low-spin isomers.
Explanations are given for the unusually high Δ value produced
by terdentate tri(2-pyridyl)amine, and for its tendency
to form diacidobis(bidentate) complexes.

Date of Award	1972
Original language	English