Fate of CH2=CHE (E = H, OMe) in the presence of unsaturated Ru(X)(H)L2q+ (X = Cl, q=0; X = CO, q=1):: Highly sensitive to X and E

DFT (B3PW91) calculations have been carried out to discuss the role of the ancillary ligand X on the transformations of ethylene and vinyl ether by RuHX(PH3)(2)(q+) (X = Cl, q = 0; X = CO, q = 1). This study follows the experimental results presented in the preceding paper. The energy of isomerization of the vinyl ether adduct into an alkoxy-stabilized carbene complex is insensitive to the nature of X, whereas the energy of isomerization of the ethylene adduct into the ethylidene complex depends significantly on X. This is interpreted as competing donations from both the metal fragment and the alkoxy group into the empty p orbital of carbene. The insertion of an olefin into the Ru-H bond to make an unsaturated 14-electron alkyl complex is calculated to be strongly endothermic for Cl and much less so for CO. This is shown to be associated with the greater stability of the olefin adduct in the presence of Cl. Insertion of methyl vinyl ether follows the same rules as ethylene. This accounts for the direct (vinyl ether) or indirect (ethylene) experimental observation of alkyl complexes with CO. The regioselectivity of the insertion is discussed, and it is shown that the methoxy group prefers to go to the a carbon of the ethyl skeleton unless a direct Ru ... O-beta interaction forming a four-member ring is possible. An energy decomposition on a model system Ru(H)(X)(PH3)(2)(OMe2)(q) (X = Cl, q = 0; X = CO, q = 1) is used to evaluate the electrostatic contribution to the Ru ... O interaction.