The crystal structure of [Mo(NCS)(CO)2(η3-C3H5)(NCMe)2]·MeCN and the reactions of {Mo(CO)2(η3-C3H5)+} containing species with symmetric alkynes

In the solid-state [Mo(NCS)(CO)2(η3-C3H5)(NCMe)2] · MeCN (1) contains a pseudo-octahedral arrangement of ligands about molybdenum, with carbonyls and nitriles in the equatorial plane and an N-bonded thiocyanate group trans to the allyl ligand. In refluxing methanol or acetonitrile both 1, and the analogous chloro-complex [MoCl(CO)2(η3-C3H5)(NCMe)2] (2) catalytically convert PhCCPh to a mixture of hexaphenylbenzene and E,E-1,2,3,4-tetraphenylbutadiene. By contrast MeO2CCCCO2Me is not oligomerised. In methanol, complex 2 dimerises 1,4-diphenylbutadiyne to Z,E-1,4,5,8-tetraphenyl-1,7-octa-3,5-diene-1,7-diyne, whereas in the presence of base both the complex and the diyne, react preferentially with the solvent to generate the [Mo2(CO)4(η3-C3H5)2(OMe)3]− anion and Z-1,4-diphenyl-3-methoxy-but-3-ene-1-yne, respectively.