Synthesis, Structures, and Reactivity of [NiFe]-H2ase Mimics Containing One Square-Planar N2S2 Ligand Bridged between Their Ni/Fe Centers through One or Two S Atoms

Abstract

To develop the biomimetic chemistry of [NiFe]-H2ases, we have successfully prepared 2 types of 16 biomimetic models for [NiFe]-H2ases by various synthetic methods. These models are new cationic complexes that contain one square-planar N2S2 ligand coordinated to a Ni atom to form a metalloligand (dsdm)Ni (H2 dsdm = N,N′-dimethyl-N,N′-bis(2-sulfanylethyl)ethylenediamine) or (dmpn)Ni (H2 dmpn = N,N′-dimethyl-N,N′-bis(2-mercaptoethyl)-1,3-propanediamine), and in turn, one or two S atoms of their metalloligands are bridged to one Fe moiety with different ligands such as t-Cl, t-I, t-PhS, t-MeO, t-MeCN, μ-H, η2-1,2-C2H2(PPh2)2(dppv), and/or η2-1,2-C6H4(PPh2)2(dppb). While all the prepared 16 model complexes are fully characterized by elemental analysis and various spectroscopic techniques, the molecular structures for 6 of the prepared models are unambiguously confirmed by X-ray crystallography, and particularly, 2 of the prepared models have been found to activate H2 under mild conditions to give the dithiolato-bridged μ-H model complexes.