title: Two pathways of proton transfer reaction to (triphos)Cu(η(1)-BH4) via a dihydrogen bond [triphos = 1,1,1-tris(diphenylphosphinomethyl)ethane].
abstract: The interaction of the η(1)-tetrahydroborate copper(i) complex (triphos)Cu(η(1)-BH4) () with proton donors [CF3CH2OH (TFE), (CF3)2CHOH (HFIP), (CF3)3COH (PFTB), PhOH, p-NO2C6H4OH (PNP), p-NO2C6H4N[double bond, length as m-dash]NC6H4OH (PNAP), CF3OH] was a subject of a combined IR spectroscopic and theoretical investigation. Spectral (Δν) and thermodynamic (ΔH) parameters of dihydrogen bond (DHB) formation were determined experimentally. The terminal hydride ligand (characterized by the basicity factor Ej(BH) = 0.87 ± 0.01) is found to be a site of proton transfer which begins with nucleophilic substitution of BH4(-) by the alcohol oxygen atom on the copper center (BH pathway). The activation barrier computed for (CF3)2CHOH in CH2Cl2 - ΔG = 20.6 kcal mol(-1) - is in good agreement with the experimental value (ΔG = 20.0 kcal mol(-1)). An abnormal dependence of the reaction rate on the proton donor strength found experimentally in dichloromethane is explained computationally on the basis of the variation of the structural and energetic details of this process with the proton donor strength. In the second reaction mechanism found (CuH pathway), DHB complexes with the initial ROH coordination to the bridging hydride lead to B-Hbr bond cleavage with BH3 elimination. "Copper assistance" via the CuO interaction is not involved. This mechanism can be evoked to explain the occurrence of proton transfer in coordinating solvents.
authors.affiliation: A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences (INEOS RAS), Vavilova 28, 119991 Moscow, Russia. shu@ineos.ac.ru.
authors.forename: I E
authors.initials: IE
authors.lastname: Golub
authors.affiliation: A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences (INEOS RAS), Vavilova 28, 119991 Moscow, Russia. shu@ineos.ac.ru.
authors.forename: O A
authors.initials: OA
authors.lastname: Filippov
authors.affiliation: A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences (INEOS RAS), Vavilova 28, 119991 Moscow, Russia. shu@ineos.ac.ru.
authors.forename: N V
authors.initials: NV
authors.lastname: Belkova
authors.affiliation: A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences (INEOS RAS), Vavilova 28, 119991 Moscow, Russia. shu@ineos.ac.ru.
authors.forename: L M
authors.initials: LM
authors.lastname: Epstein
authors.affiliation: Istituto di Chimica dei Composti Organometallici, Consiglio Nazionale delle Ricerche (ICCOM CNR), via Madonna del Piano 10, 50019 Sesto Fiorentino (Florence), Italy. maurizio.peruzzini@iccom.it.
authors.forename: A
authors.initials: A
authors.lastname: Rossin
authors.affiliation: Istituto di Chimica dei Composti Organometallici, Consiglio Nazionale delle Ricerche (ICCOM CNR), via Madonna del Piano 10, 50019 Sesto Fiorentino (Florence), Italy. maurizio.peruzzini@iccom.it.
authors.forename: M
authors.initials: M
authors.lastname: Peruzzini
authors.affiliation: A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences (INEOS RAS), Vavilova 28, 119991 Moscow, Russia. shu@ineos.ac.ru.
authors.forename: E S
authors.initials: ES
authors.lastname: Shubina