Stabilization of a Terminal Hydride through Regioselective Protonation in a Diiron Complex Inspired by [FeFe]-Hydrogenase.

Abstract

Protonation studies of the complex [Fe2(µ-pdt)(κ2-dmpe)2(CO)2] (1), inspired by the [FeFe]-hydrogenases active site cofactor, yield terminal and bridging hydrido isomers in a ratio that depends on the acid strength and steric hindrance. A terminal hydride ligand is mainly obtained in presence of weaker acids such as [HPtBu3][BF4] and [HNEt3][BF4] while a bridging isomer is predominantly formed with stronger acids such as [HPPh3][BF4] and [H(OEt2)][BF4]. The terminal isomer is comparatively stable and undergoes isomerization into the bridging hydride following first-order kinetics, with half-lives of 21 days and 3 days at room temperature and 40°C, respectively.