STRUCTURE AND THERMAL-DEGRADATION OF BIS(1,3-DIKETONATO)COBALTBISIMIDAZOLES

The crystal structure of Co(bzac)2(HIm)2. 2MeOH (I) and Co(acac)2(HIm)2 (II) were determined by x-ray diffraction. II: triclinic, space group P1BAR, Z = 2, a = 746.3(1), b = 948.2(1), c = 1396.7(2) pm, alpha = 85.18(1)-degrees, beta = 88.96(1)-degrees, gamma = 80.72(1)-degrees, R = 3.0% for a total of 2194 observed reflections. I: monoclinic, P2(1)/c, Z = 2, a = 964.2(3), b = 864.5 (2), c = 1769.8(4) pm, beta = 98.87(2)-degrees, R = 4.7% for a total of 967 observed reflections. In both compounds centrosymmetric molecules with two bidentate diketonato groups and two imidazole ligands in trans-position are present. The molecules of II are linked by N-H . . . O-bridges within layers, while in the lattice of I by the interaction with methanol molecules N-H . . . O-H . . . O-bridges are formed. The nature of the H-bridges is the deciding factor for the first step of the thermal degradation of the complexes. The N-H . . . O-bridges of II relieves the change of the acidic protons of the imidazole to the acetylacetonato ligands. Therefore in the first step acetylacetone is eliminated. No such bridges are present in the complex I. Therefore, in the first step, imidazole and methanol are removed. On heating in O-donor solvents the reaction of I is quite analogous, and this is the reason for the application of this complex as a latent initiator of the epoxide polymerisation.