title: Ligand-controlled reactivity, selectivity, and mechanism of cationic ruthenium-catalyzed hydrosilylations of alkynes, ketones, and nitriles: a theoretical study.
abstract: Density functional theory calculations with the M06 functional have been performed on the reactivity, selectivity, and mechanism of hydrosilylations of alkynes, ketones, and nitriles catalyzed by cationic ruthenium complexes [CpRu(L)(MeCN)2](+), with L = P(i)Pr3 or MeCN. The hydrosilylation of alkynes with L = P(i)Pr3 involves an initial silyl migration mechanism to generate the anti-Markovnikov product, in contrast to the Markovnikov product obtained with L = MeCN. The bulky phosphine ligand directs the silyl group to migrate to Cβ of the alkyne. This explains the anti-Markovnikov selectivity of the catalyst with L = P(i)Pr3. By contrast, the silane additions to either ketone or nitrile proceed through an ionic SN2-Si outer-sphere mechanism, in which the substrate attacks the Si center. The P(i)Pr3 ligand facilitates the activation of the Si-H bond to furnish a η(2)-silane complex, whereas a η(1)-silane complex is formed for the MeCN ligand. This property of the phosphine ligand enables the catalytic hydrosilylation of ketones and nitriles in addition to that of alkynes.
authors.affiliation: Lab of Computational Chemistry and Drug Design, Laboratory of Chemical Genomics, Peking University Shenzhen Graduate School , Shenzhen 518055, China.
authors.forename: Yun-Fang
authors.initials: YF
authors.lastname: Yang
authors.forename: Lung Wa
authors.initials: LW
authors.lastname: Chung
authors.forename: Xinhao
authors.initials: X
authors.lastname: Zhang
authors.forename: K N
authors.initials: KN
authors.lastname: Houk
authors.forename: Yun-Dong
authors.initials: YD
authors.lastname: Wu
mesh_terms: D000480:Alkynes / Q000737:chemistry*; D002384:Catalysis; D002412:Cations / Q000737:chemistry*; D007659:Ketones / Q000737:chemistry*; D008024:Ligands; D008962:Models, Theoretical; D015394:Molecular Structure; D009570:Nitriles / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*; D012821:Silanes / Q000737:chemistry*
chemical_list: D000480:Alkynes; D002412:Cations; D007659:Ketones; D008024:Ligands; D009570:Nitriles; D012821:Silanes; D012428:Ruthenium