Synthesis and reactivity of Mo-Sn compounds: X-ray crystal structure of a novel [Mo(SnCl3)(2)(CO)(2)(NCEt)(3)]

[Mo(CO)(4)(NCMe)(2)] reacts with SnCl4 in CH2Cl2 to produce a mixture of co mpounds which can be regarded as the results of oxidative addition with the elimination of CO and the formation of a Mo-Sn bond. The compound [MoCl(Sn Cl3)(CO)(3)(NCMe)(2)] 1 is the main product but others containing Mo-Sn bon d compounds can be formed also in variable amounts, as was shown by IR and NMR investigation of the reaction mixture. The structure of a novel [Mo(SnC l3)(2)(CO)(2)(NCEt)(3)] 4 was established by X-ray crystallography. This is the first structurally characterized molybdenum(II) carbonyl complex conta ining two anionic SnCl3 ligands and the very rare example of the 4:3 piano stool seven-coordinate geometry. In the reaction of I with alkynes, complex es were isolated in which CO and/or acetonitrile ligands were replaced by a lkyne ligands. The alkyne molybdenum(II) complexes formed were characterize d structurally by IR and NMR spectroscopy. However, the reaction of 1 with phenylacetylene leads to the catalytic coupling of alkyne molecules and the formation of cycloligomers and polymers. The possible mechanisms for the f ormation of molybdenum(II) complexes and their role in the catalytic proces s are discussed. (C) 1999 Elsevier Science S.A. All rights reserved.