Iron pyridine-2-thiolate complexes

The reaction of bis(2-pyridyl) disulfide with [HFe(CO)4]- affords [Fe(CO)4(SC5H4N)]-, in which the pyridine-2-thiolate ligand is bound in a monodentate (S-bonded) mode. Oxidative addition of bis(2-pyridyl) disulfide to [Fe(CO)4(SC5H4N)]- and concomitant displacement of [SC5H4N]- leads to the neutral monomeric compound cis-[Fe(CO)2(SC5H4N)2]. In the presence of [SC5H4N]- in CH3CN at 60°C, cis-[Fe(CO)2(SC5H4N)2] undergoes facile conversion to d6 Fe(II) high-spin [Fe(SC5H4N)3]-. Reduction of cis-[Fe(CO)2(SC5H4N)2] and [Fe(SC5H4N)3]- under CO at room temperature with [BH4]-/[Nα][benzophenone] affords the monodentate (S-bonded) complex [Fe(CO)4(SC5H4N)]-. The results are consistent with sulfur-donor atom stabilization of the lower oxidation states of iron, while the S,N-chelating pyridine-2-thiolate ligand enhances the stability of iron in the higher oxidation state.