Abstract
Many new compounds of chromium(II) and vanadium(II) have been prepared and their magnetic behaviour and visible, infra-red and far infra-red spectra studied. Owing to the extreme sensitivity of such compounds to oxygen it has been necessary to handle these compounds in nitrogen or in vacuo. Methyl-substituted and halogen-substituted pyridine complexes of chromium(II) have been prepared for the first time, two kinds have been obtained: mononuclear complexes, ML[4]X[2], where L = ligand and X = halide, and polynuclear complexes, ML[2]X[2]. The tetrakis(amino) complexes are normal, high-spin chromium(II) while the bis(amine) complexes are halide-bridged, polynuclear compounds in which antiferromagnetic interactions occur. The following compounds: Cr(3-bromopyridihe)[2]I[2], Cr(3-iodopyridine)[2]I[2], and Cr(3,5-dichloropyridine)[2]I[2] seem to be the first chromium(II) complexes in which iodide acts as a bridging group. Reflectance spectra of all three complexes indicate that they have distorted octahedral structures. Vanadium(II) chemistry is little known and a series of new complexes of beta and gamma-picolines with vanadium(II) have been prepared. These are of two types, V(picoline)[4]X[2], where X is Cl, Br or I and V(picoline)[2]Br[2]. The former are tetragonally-distorted vanadium(II) compounds as a result of non-equivalent ligands: the latter are halide-bridged polynuclear compounds in which antiferromagnetic interactions occur. Conditions for the preparation of chloride and iodide bridged complexes could not be found. From the splitting of bands in their reflectance spectra, these complexes have been found to have considerably distorted octahedral structures. Whereas the tetrakis(amine) complexes have weak axial fields, the bis(amine) complexes have strong axial fields. Investigation of complex formation by vanadium(II) with 1,2-diatnino-propane and 1,3-diarainopropane have been carried out. Only tris(amine) compounds of these ligands have been obtained, although attempts were made to prepare bis(amine) complexes by thermal decomposition. These have magnetic moments a little below the spin-only value which vary little with the temperature. Their diffuse reflectance spectra show the three spin-allowed d-d bands expected in octahedral symmetry, although the third band is partly obscured by charge transfer or ligand bands. The far infra-red spectra of chromiura(II) halogen-substituted pyridines and vanadium(II) methyl-substituted pyridines have been done. The metal-halogen frequencies in the region of 324-180 cm.[-1] for chromium(II) and 306-210 cm.[-1] for vanadium(II) have been investigated.