Abstract

BETANZOS-LARA, Soledad; HABTEMARIAM, Abraha  and  SADLER, Peter J.. Transfer Hydrogenation Reactions of Photoactivatable N,N'-Chelated Ruthenium(II) Arene Complexes. J. Mex. Chem. Soc [online]. 2013, vol.57, n.3, pp.160-168. ISSN 1870-249X.

We show that the reaction of Ru^II arene chlorido complexes of the type [(η⁶-arene)Ru(N,N')Cl]⁺ arene = p-cymene (p-cym), hexamethylbenzene (hmb), indane (ind), N,N' = bipyrimidine (bpm) and 1,10-phenanthroline (phen) with excess sodium formate generates a very stable formate adduct through spontaneous hydrolysis of the Ru-Cl bond at 310 K and pH* = 7.0. The formate adducts are also produced when Ru^II arene pyridine complexes of the type [(η⁶-arene)Ru(N,N')(Py)]²⁺ (where Py = pyridine), are irradiated with UVA (λ_irr = 300-400 nm) or visible light (λ_irr = 400-660 nm) under the same conditions. The Ru^II arene formato adducts do not catalyse the reduction of acetone through transfer hydrogenation. However, all the complexes (except complex 2 which contains phen as the chelating ligand) can catalyse the regioselective reduction of NAD⁺ in the presence of formate (25 mol equiv) in aqueous solution to form 1,4-NADH. The catalytic activity is dependent on the nature of the chelating ligand. Most interestingly, the regioselective reduction of NAD⁺ to 1,4-NADH can be also specifically triggered by photoactivating a Ru^II arene Py complex.

Keywords : Ruthenium; arene; pyridine; hydride; NAD⁺/NADH; photoactivation.

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