Bonding analysis and the mechanisms on the ring-opening of alkoxy-bridged bis(silylene) transition-metal complexes toward MeOH

The mechanistic study on the ring-opening of alkoxy-bridged bis(silylene) transition-metal complexes toward MeOH is performed by using density functional theory. Four steps are predicted to be involved in the reaction, formation of hydrogen bonding between R and a MeOH, ring-opening of the Ru-Si1-O1-Si2 four-membered ring, formation of the six-membered ring, and the hydroxyl hydrogen migration to the metal center. It is found that the reaction is favorable thermodynamically and the hydroxyl hydrogen migration is the rate-determining step. Systematic variations of the structural parameters involved in the reaction mechanism are revealed, which revealed the relationship of the bond strength among Ru-Si, Si-O and O-H bonds. (C) 2007 Elsevier B. V. All rights reserved.