Efficient Nicotinamide Adenine Dinucleotide Regeneration with aRhodium-Carbene Catalyst and Isolation of a Hydride Intermediate br

Abstract

Regeneration of nicotinamide adenine dinucleotide(NADH) has been the primary interest in thefield of enzymatictransformation, especially associating oxidoreductases given thestoichiometric consumption. The synthesized carbene-ligatedrhodium complex [(eta 5-Cp*)Rh(MDI)Cl]+[Cp*= pentamethyl-cyclopentadienyl; MDI = 1,1 '-methylenebis(3,3 '-dimethylimidazo-lium)] acts as an exceptional catalyst in the reduction of NAD+toNADH with a turnover frequency of 1730 h-1, which is over twicethat of the higher catalytic activity of the commercially availablecatalyst [Cp*Rh(bpy)Cl]+(bpy = 2,2'-bipyridine). Offsetting thecontentious atmosphere currently taking place over the specificintermediate of the NADH regeneration, this study presentspivotal evidence of a metal hydride intermediate with abis(carbene) ligand: a stable form of the rhodium hydride intermediate, [(eta 5-Cp*)Rh(MDI)H]+, was isolated and fullycharacterized. This enables thorough insight into the possible mechanism and exact intermediate structure in the NAD+reductionprocess