The reaction of nitric oxide with some transition metal chelates.

This thesis describes the preparation and investigation of some Schiff''s base complexes of cobalt(II), iron(II), manganese(II), and chromium, and of the products of their reaction with nitric oxide. The Schiff's bases are quadri-dentate, e.g. NN'ethylenebis(salicylideneimine) and several of its ring-substituted derivatives, and bidentate N-phenyl- and N-methylsalicylaldimines. The cobalt(II) complexes of bidentate ligands are spin free and of quadridentate ligands are mostly spin-paired. The exceptions with quadridentate ligands show magnetic behaviour compatible with spin-paired, spin-free equilibria. Magnetic studies of two monohydrates suggest that the water molecule is co-ordinated. The cobalt nitrosyls all show Temperature Independent Paramagnetism with fractional magnetic moments (~ 0.6 B.M.). The iron(I) Schiff's base complexes are all spin-free, as are the mononitrosyls at room temperature. Nitrosyl NN'ethylenebis(salicylideneiminato) iron changes sharply to a spin-paired state at approximately 180+/-K with a corresponding decrease in the N-O stretching frequency. Various reasons are discussed. Low temperature infra-red studies show that the 5-nitro substituted nitrosyl changes to give some of the spin-paired species at liquid air temperature. The other nitrosyls studied all obeyed the Curie-Weiss law. These compounds probably constitute the most stable series of spin-free iron nitrosyls so far discovered. No correlation has been found between the substituent and the N-O stretching frequency, NN'ethylenebis(salicylideneiminato) manganese(II) has been prepared pure for the first time, and a discontinuity in the temperature versus 1/X' M plot has not been confirmed. The reaction with nitric oxide gives an oxidised product, NN'ethylenebis(salicylideneiminato) manganese(III) acetate, which is spin-free and obeys the Curie-Weiss law. Some preliminary investigations of the corresponding chromium(II) system have been carried out