title: Dihydrogen bonding in complex (PP3)RuH(η(1)-BH4) featuring two proton-accepting hydride sites: experimental and theoretical studies.
abstract: Combining variable-temperature infrared and NMR spectroscopic studies with quantum-chemical calculations (density functional theory (DFT) and natural bond orbital) allowed us to address the problem of competition between MH (M = transition metal) and BH hydrogens as proton-accepting sites in dihydrogen bond (DHB) and to unravel the mechanism of proton transfer to complex (PP3)RuH(η(1)-BH4) (1, PP3 = κ(4)-P(CH2CH2PPh2)3). Interaction of complex 1 with CH3OH, fluorinated alcohols of variable acid strength [CH2FCH2OH, CF3CH2OH, (CF3)2CHOH (HFIP), (CF3)3COH], and CF3COOH leads to the medium-strength DHB complexes involving BH bonds (3-5 kcal/mol), whereas DHB complexes with RuH were not observed experimentally. The two proton-transfer pathways were considered in DFT/M06 calculations. The first one goes via more favorable bifurcate complexes to BHterm and high activation barriers (38.2 and 28.4 kcal/mol in case of HFIP) and leads directly to the thermodynamic product [(PP3)RuHeq(H2)](+)[OR](-). The second pathway starts from the less-favorable complex with RuH ligand but shows a lower activation barrier (23.5 kcal/mol for HFIP) and eventually leads to the final product via the isomerization of intermediate [(PP3)RuHax(H2)](+)[OR](-). The B-Hbr bond breaking is the common key step of all pathways investigated.
authors.affiliation: A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences , 28 Vavilov Street, 119991 Moscow, Russia.
authors.forename: Natalia V
authors.initials: NV
authors.lastname: Belkova
authors.forename: Ekaterina V
authors.initials: EV
authors.lastname: Bakhmutova-Albert
authors.forename: Evgenii I
authors.initials: EI
authors.lastname: Gutsul
authors.forename: Vladimir I
authors.initials: VI
authors.lastname: Bakhmutov
authors.forename: Igor E
authors.initials: IE
authors.lastname: Golub
authors.forename: Oleg A
authors.initials: OA
authors.lastname: Filippov
authors.forename: Lina M
authors.initials: LM
authors.lastname: Epstein
authors.forename: Maurizio
authors.initials: M
authors.lastname: Peruzzini
authors.forename: Andrea
authors.initials: A
authors.lastname: Rossin
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Zanobini
authors.forename: Elena S
authors.initials: ES
authors.lastname: Shubina