Crystalline-State Reaction of Cobaloxime Complexes. 18. Metastable Intermediate Structure Observed by a New X-Ray Diffractometer for Rapid Data Collection

Article abstract of DOI:10.1246/bcsj.68.2517

A crystal of <(R)-1,2-bis(methoxycarbonyl)ethyl>bis(dimethylglyoximato)(diphenylmethylphosphine)cobalt(III) changes its cell dimensions with retention of the single crystal form on exposure to visible light.The change is so fast that a new type of diffractometer (IPD-WAS) was developed for rapid data collection.The structures were analyzed at four different stages of the change using the diffractometer, which enabled us to collect the three-dimensional intensity data within 2 h.The cell dimensions of the monoclinic crystal varied from a = 13.678(2), b = 24.880(6), c = 9.391(2) Angstroem, β = 107.99(1) deg, and V = 3040(1) Angstroem³ to a = 13.56(1), b = 25.06(1), c = 9.381(6) Angstroem, β = 107.35(6) deg, and V = 3044(3) Angstroem³.The space group was changed from P2₁ to P2₁/n.The structures at four stages showed that there are two crystallographically independent molecules, A and B, in an asymmetric unit of the crystal before irradiation and that the chiral 1,2-bis(methoxycarbonyl)ethyl (bmce) group of the B molecule is completely inverted to the opposite configuration while the chiral bmce group of the A molecule remains unaltered after irradiation.This brings about an inversion center between the two molecules.The reaction cavity for the B bmce group is significantly greater than that for the A bmce group.At the intermediate stages, the B bmce group takes complicated disordered structures, which indicates that there exists a metastable intermediate structure in the inversion process.