Theoretical Study for the Reactions of (Silyl)(silylene)tungsten and -molybdenum Complexes with Ethylene Sulfide

The reaction mechanisms of the (silyl)­(silylene)­tungsten
and -molybdenum
complexes Cp*­(OC)2M­(SiMe3)­(SiMes2) (M = W (1), Mo (2); Cp* = η5-C5Me5; Mes = 2,4,6-Me3C6H2) with the sulfur donor reagent ethylene sulfide 3 have been explored by ab initio molecular orbital and DFT
(B3LYP) methods. As a result, the metal–ligand interactions
were found to be stronger in the tungsten complexes than in the molybdenum
complexes. Therefore, in the early stages which are common for both
tungsten and molybdenum complexes, the energy barriers of the reactions
of the tungsten tend to be higher than those of the molybdenum. The
insertion of a sulfur atom into the metal–ligand bond takes
place more easily in the molybdenum complex in comparison to that
in the tungsten complex. This is the plausible reason parts of the
reaction mechanisms and the final products are different between the
W and Mo complexes.