Hydride Reduction of NAD(P)⁺ Model Compounds with a Ru(II)–Hydrido Complex

Abstract

In order to better understand the regioselective hydride transfer of metal hydrido complexes to NAD(P)+ model compounds, reactions of [Ru(tpy)(bpy)H]+ (Ru-H: tpy = 2,2′:6″,2″-terpyridine, bpy = 2,2′-bipyridine) with various substituent NAD(P)+ model compounds were investigated in detail. All of the NAD(P)+ model compounds accepted hydride from Ru-H, yielding 1:1 adducts, where the dihydro form(s) of the model compounds coordinated with the carbamoyl group to the Ru(II) center of [Ru(tpy)(bpy)]2+, with very different reaction rates. Some reactions produced the adduct with only the 1,4-dihydro structure, whereas others produced a mixture of two adducts, with a 1,4- or 1,2-dihydro structure. In particular, temperature-dependent adduct formation kinetics studies provided important information on the transition state(s) of the hydride transfer reactions and factors for determining the regioselectivity. Most adducts were cleaved to the corresponding free dihydro product(s) with the same distribution of the regioisomers to the adduct(s).