SOLVENT EFFECTS ON THE MODE OF CO-ORDINATION OF THE THIOCYANATE ION, A STUDY ON SOME BIS(DIMETHYLGLYOXIMATO)THIOCYANATOCOBALT(III) COMPLEXES

The preparation and structure of some 20 complexes of the type [Co(dh)2L(SCN)](dh = dimethylgloximato; L = various pyridines and anilines, H2O, NH3, Me2N·CHO, Ph3P), H[Co(dh)2X(SCN)](X = Cl–, Br–, or SCN–), or Et4N[Co(dh)2NO2(NCS)] are described. It is shown that, for the substituted pyridine and aniline complexes, the equilibrium [Co(dh)2L(SCN)]⇌[Co(dh)2L(NCS)] exists in solution, and that it lies to the right for solvents with higher dielectric constants, and to the left for solvents with lower dielectric constants. This behaviour is explained in a way which also reconciles the reverse behaviour of thiocyanato-complexes of class ‘b’ metals.