STRUCTURES OF (BETA-CYANOETHYL)(3-ETHYLPYRIDINE)BIS(DIMETHYLGLYOXIMATO)COBALT(III) AND (BETA-CYANOETHYL)(4-ETHYLPYRIDINE)BIS(DIMETHYLGLYOXIMATO)COBALT(III)

(1): [Co(C3H4N)(C7H9N)(C4H7N2O2)2] M(r) = 450.38, monoclinic, P2(1)/n, a = 19.570 (2), b = 9.288 (2), c = 11.644 (2) angstrom, beta = 92.37 (2)degrees, V = 2114.6 (6) angstrom 3, Z = 4, D(x) = 1.415 g cm-3, lambda(Mo K-alpha) = 0.71069 angstrom, mu = 7.91 cm-1, F(000) = 944, T = 298 K, R = 0.071 for 3079 independent reflections. (2): [Co(C3H4N)(C7H9N)(C4H7N2O2)2], M(r) = 450.38, triclinic, P1BAR, a = 11.247 (6), b = 11.230 (4), c = 9.416 (2) angstrom, alpha = 93.17 (7), beta = 114.20 (2), gamma = 99.45 (5)degrees, V = 1060.0 (8) angstrom 3, Z = 2, D(x) = 1.416 g cm-3, lambda(Mo K-alpha) = 0.71069 angstrom, mu = 7.91 cm-1, F(000) = 472, T = 298 K, R = 0.057 for 3241 independent reflections. In each crystal the beta-cyanoethyl group adopts a conformation which is parallel to the cobaloxime plane. The size of the cavity for the beta-cyanoethyl group in crystal (2) is significantly greater than that in crystal (1). This explains the greater isomerization rate of (2) than that of (1) on exposure to visible light.