Substituted pyridine complexes of the first row transition metals

A number of complexes of the first row transition metal halides and pseudohalides in the 2 oxidation state with pyridine and substituted pyridines have been prepared. These have taken the form ML4X2 (where M= Ni, L =pyridine, 3-methyIpyridine, 4-methyl-pyridine, 3,5-lutidine, 4-vinylpyridine, 3-chloropyridine and isoquinoline, X= Cl, Br, I, NCS, NCO; Fe, Co, L-4-vinyl- pyridine, X= Cl, Br, I, NCS, NCO) and ML2X2 (where M=Ni, L = pyridine 3-methylpyridine, 4-methylpyridine, 3,5-lutidine, 4-vinylpyridine, 3-bromopyridine, X=Cl, Br, NCS, N3; M=Mn, Fe, Co, Cu, Zn, L= 4-vinylpyridine, 2-vinylpyridine, X= Cl, Br, I, NCS, NCO, N3). These complexes have been examined using techniques of i. r. , far i. r. and Raman spectroscopy, U. V. and visible spectroscopy and magnetochemistry in an attempt to correlate the structures with the spectral measurements. The nickel(Il) complexes were treated in greater detail since an attempt to relate changes in visible spectral parameters with donor properties of the ligands was made; and to this end values of the ligand-field splitting parameters in the xy plane and along the z axis, i. e. DqXY and Dqz were evaluated from the splitting of the spin-allowed bands observable in the electronic spectrum. A linear relationship was found between the spectral parameters in the xy plane and along the z axis, and this was interpreted as meaning that a change in length of the bonds in the xy plane would effect the length of the bonds along the z axis. The lengths of the bonds would in turn be related to the donor properties of the ligands. A previous report that the vinyl group of 2-vinylpyridine will co-ordinate to copper (Il) has not been confirmed.