Structural aspects of a vitamin B12 model. Crystal and molecular structure of trans-cyanobis(dimethylglyoximato)(trimethyl phosphite)-cobalt(III)

Abstract

Crystals of the title complex [Co(Hdmg)₂(CN){P(OMe)₃}] are monoclinic, space group P2₁/c, with a= 18.431(9), b= 14.082(7), c= 17.651(9)Å, β= 121.66(8)°, and Z= 8. The intensities of 3 978 independent reflections [I, 3σ(I)] recorded on an automatic diffractometer have been used to solve and refine the structure to R 0.059. The axial (MeO)₃P–Co–CN fragments are almost equivalent in the two crystallographically independent pseudooctahedral molecules with mean Co–P, Co–C distances and P–Co–C angle of 2.225(3), 1.909(8)Å, and 177.8(3)° respectively. The Co–C bond length is the shortest so far reported in organocobaloximes. The trans influence of X for the seriesof complexes [Co(Hdmg)₂X{P(OMe)₃}](X = Cl, CN, or CH₃) increases in the order Cl < CN < CH₃. A comparison is made of the co-ordination environment of the cobalt atom in cobaloximes and cobalamins.