[Fe ₂ (μ-S ₂ )(CN) ₂ (CO) ₄ ] ^2– , [Fe ₂ (μ-SH) ₂ (CN) ₂ (CO) ₄ ] ^2– , and [Fe ₂ (μ-SH)(μ-SCH ₂ NH ₂ )(CN) ₂ (CO) ₄ ] ^2– Related to the Biosynthesis of 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.