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 geometr y of the metal coordination sphere conforms to a distorted capped octahedro n with a carbonyl group in the unique capping position. The capped face con tains two carbonyl ligands and an iodo group, the uncapped face two MeCN li gands and an iodo group. The low temperature C-13 n.m.r. spectrum (-70 degr ees C, CD2Cl2) shows a single band at delta = 222.8 ppm, which suggests tha t 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) c omplex mer-[MoI3(NCMe)(3)] (2) in quantitative yield.