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.