Molecular structure and iodine oxidative-thermal decarbonylation of the seven-coordinate complex [MoI2(CO)3(NCMe)2] to give the crystallographically characterised complex mer-[MoI3(NCMe)3]

The X-ray crystal structure of the seven-coordinate complex [Mol(2)(CO)(3)(NCMe)(2)] (1) has been determined and shows discrete molecules. The geometry of the metal coordination sphere conforms to a distorted capped octahedron with a carbonyl group in the unique capping position. The capped face contains two carbonyl ligands and an iodo group, the uncapped face two MeCN ligands and an iodo group. The low temperature C-13 n.m.r. spectrum (-70 degrees C, CD2Cl2) shows a single band at delta = 222.8 ppm, which suggests that the complex is rearranging more rapidly than the n.m.r. timescale at this temperature. Refluxing a 2:1 mixture of [MoI2(CO)(3)(NCMe)(2)] and I-2 in MeCN for 2 h gives the crystallographically characterised molybdenum(III) complex mer-[MoI3(NCMe)(3)] (2) in quantitative yield.