[Fe₂(μ‑S₂)(CN)₂(CO)₄]^2–, [Fe₂(μ-SH)₂(CN)₂(CO)₄]^2–, and[Fe₂(μ-SH)(μ-SCH₂NH₂)(CN)₂(CO)₄]^2– Related to the Biosynthesisof the [2Fe]_H Site of the [FeFe]Hydrogenases

Abstract

This paper discusses diiron complexes implicated as intermediates in the biosynthesis of the [2Fe]_H site of the [FeFe]-hydrogenases. These complexes include [Fe₂(μ-SH)(μ-SR)(CN)₂(CO)₄]^2– (R = H, CH₂NH₂ [2^H,R]^2–), which are available from the new precursor [Fe₂(μ-S₂)(CN)₂(CO)₄]^2– ([1]^2–). Complex [1]^2– was prepared by treating Fe₂(μ-S₂)(CO)₆ with two equiv of KN(tms)₂. Access to [2^H,R]^2– involves the reaction of [1]^2– with LiBHEt₃ followed by quenching with the equivalent of R⁺. Similarly, access to [Fe₂(μ-SMe)(μ-SCH₂NHFmoc)(CN)₂(CO)₄]^2– ([2^Me,CH2NHFmoc]^2–) involves treating [1]^2– with MeLi, followed by quenching with FmocNHCH₂OAc. As established by ¹⁵N-labeling, deprotection of [2^H,CH2NHFmoc]^2– gave the azadithiolate [Fe₂[(μ-SCH₂)¹⁵NH](CN)₂(CO)₄]^2– ([4¹⁵N]^2–) and ¹⁵NH₃.