Ruthenium p-cymene iminophosphonamide complexes: activation under basic conditions and transfer hydrogenation catalysis

Sinopalnikova, I.S.; Peganova, T.A.; Belkova, N.V.; Deydier, E.; Daran, J.C.; Shubina, E.S.; Kalsin, A.M.; Poli, R.

Авторы: Sinopalnikova I.S., Peganova T.A., Belkova N.V., Deydier E., Daran J.C., Shubina E.S., Kalsin A.M., Poli R.
Журнал: European Journal of Inorganic Chemistry
Год издания: 2018
Издательство: John Wiley & Sons Ltd.
Местоположение издательства: United Kingdom
Первая страница: 2285
Последняя страница: 2299
DOI: 10.1002/ejic.201701344
Аннотация: Complex [(η6-Cym)RuCl(NPN)] {Cym = p-cymene; NPN = (p-TolN)2PPh2} (1) yields a thermally sensitive hydride derivative [(η6-Cym)RuH(NPN)] (2) by reaction with iPrOH in the presence of a strong base, via an observable isopropoxide intermediate [(η6-Cym)Ru(OiPr)(NPN)] (3), or with NaBHEt3 in THF. Partial conversion also occurs in iPrOH in the absence of base. 2 is stabilized by dihydrogen bonding with isopropanol, but attempts to isolate it induce isomer¬ization by hydride migration to a ring CH position to yield a 16-electron cyclohexadienyl derivative [{η5-p-C6H5(Me)(iPr)}Ru(NPN)], which has been crystallographically characterized as a disordered mixture of two regioisomers (4/4’). Complex 2 is able to release H2 upon treatment with medium strength proton donors (fluorinated alcohols), but also slowly with iPrOH. 2 is an active catalyst for the transfer hydrogenation of acetophenone to phenylethanol in isopropanol. The catalytic transformation is first order in acetophenone and first order in catalyst, with k = 117±10 M-1 h-1 at 40°C. The temperature dependence of the rate constant (25-80°C) gave the activation parameters ΔH‡ = 9.6±1.3 kcal mol-1 and ΔS‡ = -31±4 cal mol-1 K-1. DFT calculations have validated the slow isomerization of 2 to 4/4’ (high energy TS), the preference of the cyclohexadienyl system for 4/4’ relative to the other isomers 4Me and 4iPr, where the hydride has migrated to the CMe or CiPr position, and suggest that the hydrogen transfer mechanism involves outer sphere hydride transfer to the ketone substrate with H-bonding assistance of isopropanol to yield a σ-complex intermediate [(η6-Cym)Ru+(NPN){H-C(Me)(Ph)O-}].
Добавил в систему: Кальсин Александр Михайлович

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Ruthenium p-cymene iminophosphonamide complexes: activation under basic conditions and transfer hydrogenation catalysisстатья

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