Bifunctional activation of amine-boranes by the W/Pd bimetallic analogs of “frustrated Lewis pairs” |
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| Authors: | Elena S Osipova Ekaterina S Gulyaeva Evgenii I Gutsul Vladislava A Kirkina Alexander A Pavlov Yulia V Nelyubina Andrea Rossin Maurizio Peruzzini Lina M Epstein Natalia V Belkova Oleg A Filippov Elena S Shubina |
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| Institution: | A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences (INEOS RAS), Vavilova Str. 28, 119991 Moscow Russia.; Istituto di Chimica dei Composti Organometallici – Consiglio Nazionale delle Ricerche (ICCOM – CNR), Via Madonna del Piano 10, 50019 Sesto Fiorentino Italy, |
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| Abstract: | The reaction between basic (PCP)Pd(H)] (PCP = 2,6-(CH2P(t-C4H9)2)2C6H4) and acidic LWH(CO)3] (L = Cp (1a), Tp (1b); Cp = η5-cyclopentadienyl, Tp = κ3-hydridotris(pyrazolyl)borate) leads to the formation of bimolecular complexes LW(CO)2(μ-CO)⋯Pd(PCP)] (4a, 4b), which catalyze amine-borane (Me2NHBH3, tBuNH2BH3) dehydrogenation. The combination of variable-temperature (1H, 31P{1H}, 11B NMR and IR) spectroscopies and computational (ωB97XD/def2-TZVP) studies reveal the formation of an η1-borane complex (PCP)Pd(Me2NHBH3)]+LW(CO3)]− (5) in the first step, where a BH bond strongly binds palladium and an amine group is hydrogen-bonded to tungsten. The subsequent intracomplex proton transfer is the rate-determining step, followed by an almost barrierless hydride transfer. Bimetallic species 4 are easily regenerated through hydrogen evolution in the reaction between two hydrides.Bimetallic complexes LW(CO)2(μ-CO)⋯Pd(PCP)] cooperatively activate amine-boranes for their dehydrogenation via N–H proton tunneling at RDS and H2 evolution from two neutral hydrides. |
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