Reversible carbonylation of [2Fe2S] model complexes with pendant quinoline or pyridine arms

Reaction of (μ-SLi)2Fe2(CO)6 with 2-(chloromethyl)quinoline yielded four [2Fe2S] complexes, namely [(μ-SCH2C9H6N)(μ-SCH2C9H6N-η1)Fe2(CO)5] (1), [(μ-SEt)(μ-SCH2C9H6N-η1)Fe2(CO)5] (2), [(μ-SCH2C9H6N)2Fe2(CO)6] (3) and [(μ-SEt) (μ-SCH2C9H6N)Fe2(CO)6] (4) as mimics for the active site of [FeFe]-hydrogenase. An analogous reaction with 2-(chloromethyl)pyridine afforded [(μ-SEt)(μ-SCH2C5H4N-η1)Fe2(CO)5] (5) which readily reacted with CO to give [(μ-SEt)(μ-SCH2C5H4N) Fe2(CO)6] (6). X-ray crystallographic studies reveal that in 1, 2 and 5, the pendant quinoline and pyridine ligands are ligated to the Fe atoms. Reversible carbonylation of 1, 2 and 5, involving cleavage of the pendant Fe–N bond was monitored by IR spectroscopy. Protonation of complexes 1–5 with HBF4·OEt2 was also investigated by IR spectroscopy.