The Bridging Acetylene to Bridging Vinylidene Rearrangement in a Triruthenium Carbonyl Cluster: A DFT Mechanistic Study

Abstract

A DFT computational study on the reaction that transforms the triruthenium cluster [Ru3(μ3-κ2-HNNMe2)(μ3-κ2-HCCH2)(μ-κ2-HCCH)(CO)7] (1), which contains an edge-bridging acetylene ligand, into the derivative [Ru3(μ3-κ2-HNNMe2)(μ3-κ2-HCCH2)(μ-κ1-CCH2)(CO)7] (2), which contains an edge-bridging vinylidene ligand, is reported. The reaction pathway with the lowest energy barrier (pathway 1, 37.4 kcal mol−1) is a four-step process that releases 10.7 kcal mol−1. It involves the participation of a hydrido-alkynyl intermediate (arising from the oxidative addition of an acetylene C−H bond). It has been shown that the polymetallic (at least bimetallic) nature of the system and the hemilabile character of the face-capping vinyl ligand play important roles in the operating mechanism. Seven alternative reaction pathways, one of them also involving an acetylene C−H oxidative addition mechanism and the remaining six involving a 1,2-hydrogen-shift of an H atom of the edge-bridging acetylene, were also found to connect com...