Abstract
This thesis describes the preparation and investigation of a number of copper(II) and chromium(II) compounds. Copper(II) and chromium(II) compounds are expected to show structural and magnetic similarities and it was intended to extend previous work on copper(II) carboxylates and to investigate, for the first time, various aspects of chromium(II) chemistry. A scheme has been suggested for distinguishing mono-, bi- and poly-nuclear structures in copper(II) compounds and several assignments made. Following the procedure of Kambe magnetic results have been used to determine the exchange integrals of the binuclear copper(II) carboxylates studied and these have been related to the pKa values of the parent acids. The preparation of compounds of chromium(II) presents considerable experimental difficulty because of rapid aerial oxidation, and to overcome this special apparatus has been used. Several new compounds of chromium have been prepared (in all 23 compounds and some anhydrous compounds) and their magnetic properties studied over a wide range of temperature. A preliminary investigation of spectral properties has also been made. The magnetic properties of several simple salts show their magnetic moments to be close to the anticipated spin only value of 4.9 B.M. The possible effects of Jahn-Teller distortions on octahedral complexes has been considered but the results are inconclusive. Chromous monocarboxylates have been shown to be dimeric and presumably analogous to copper(II) and chromium(II) acetates. Owing, however, to the unavoidable presence of traces of chromium(III) it has not been possible to estimate their exchange integrals accurately. Chromium(II) formate has been prepared in two forms, a blue, monomeric form and a red, dimeric form. The work has so far been the subject of two publications : Earnshaw, Larkworthy and Patel, Proc. Chem. Soc. , 281 (1963). Earnshaw, Larkworthy and Patel, Z.anorg.Chem.(in press).