Molybdenum hydrocarbyl

Tertiary phosphines or phosphites L promote insertion of carbon monoxide into the molybdenum-hydrocarbyl bond of Moltj -CsHjlRfCOls ... 

The results in Table V show that active disproportionation catalysts are obtained when molybdenum and tungsten hydrocarbyls are supported on silica or alumina. These catalytic systems have not been optimized, and it is highly probable that more active catalysts based on these systems can be obtained. No obvious pattern emerges from the results both silica and alumina supports confer activity on the organometallic compounds which are themselves inactive in homogeneous solution under similar conditions. 

CH2=C=CPh)] (39b). The latter two complexes display very similar structural characteristics. Both complexes contain hydrocarbyl ligands in which i/(CH2-C) exceeds /(C-CR). For instance, in the molybdenum complex these distances are 1.380(2) A and 1.263(4) A, whereas those reported by Wojcicki are 1.39(2) and 1.23(1) A. Such data were interpreted in terms of a large contribution from the 17 -propargyl resonance structure [105(1) and 39(1)), respectively]. However, values of 7ch indi-... 

For the more general case, a coordinatively unsaturated intermediate of type A resulting from migration of the hydrocarbyl group may be stabilized in a number of ways . It has been pointed out that for CO insertion into the methyl-molybdenum bond of Me—Mo( -C5H5)(CO)3 [reaction (b)], which has been studied in tetrahydrofuran (THF) and in methyl-substituted THFs, the rate constant of the migratory step /ci significantly increases with the donicity of the solvent (the methyl-substituted THFs differ in donicity but have similar dielectric constants). 

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