Ferracyclic carbamoyl complexes related to the active site of [Fe]-hydrogenase

Abstract

The active site of the [Fe]-hydrogenase features an iron(II) centre bearing cis carbonyl groups and a chelating pyridine-acyl ligand. Reproducing these unusual features in synthetic models is an intriguing challenge, which will allow both better understanding of the enzymatic system and more fundamental insight into the coordination modes of iron. By using the carbamoyl group as a surrogate for acyl, we have been able to synthesize a range of ferracyclic complexes. Initial reaction of Fe(CO)4Br2 with 2-aminopyridine yields a complex bearing a labile solvent molecule, which can be replaced by stronger donors bearing phosphorus atoms to produce a number of derivatives. Introduction of a hydroxy group using this method is unsuccessful both with a free OH group and when this is silyl-protected. In contrast, the analogous reactions starting from 2,6-diaminopyridine does allow synthesis of complexes bearing a pendant basic group.

Novel reactions of homodinuclear Ni2complexes [Ni(RNPyS4)]2with Fe3(CO)12to give heterotrinuclear NiFe2and mononuclear Fe complexes relevant to [NiFe]- and [Fe]-hydrogenases

“…51,66,67 The electrochemical properties of our model complexes 3a-3e were also investigated in MeCN with n-Bu 4 PF 6 as the electrolyte by CV techniques. Fig.…”

Hydrogenase Enzymes and Their Synthetic Models: The Role of Metal Hydrides

“…Synthetic investigations into 2-pyridylcarbamoyl 405,406 and pyridylacyl complexes have afforded models closely resembling the CO-inhibited [Fe]-H 2 ase active site. Indeed, this motif has been incorporated into complexes of the form [Fe(CO) 2 (2-pyridinethiolate)(2-pyridylacetyl)] ([ 54 – 56 ], Figure 53), which feature donors resembling the native ligands, with an additional N-donor.…”

Mimicking hydrogenases: From biomimetics to artificial enzymes

“…More relevant mimics of the active site of [Fe]-hydrogenase were reported more recently, in which the acyl functionality is part of either an acylmethylpyridine ligand [177], a 2-acylmethyl-6-methoxypyridine ligand [178][179][180] or 2-acylmethyl-6hydroxymethylpyridine ligand [181]. In this context, the approach taken by Pickett and coworkers, in which the construction of an [Fe]-mimic is achieved using a pyridinecarbamoyl ligand (63), is of particular interest as it results in a mono iron complex whose metrical data is remarkably close to that of the active site found in the enzyme (Figure 24) [182,183]. To date however the closest model of this active site, which reproduces the exact square-pyramidal iron coordination sphere of the natural system (64), was reported by the group of Hu [184], although their model lacked the naturally occurring acylmethylpyridone ligand.…”