title: Iron carbonyl sulfides, formaldehyde, and amines condense to give the proposed azadithiolate cofactor of the Fe-only hydrogenases.
abstract: The azadithiolate (SCH2NHCH2S) cofactor proposed to occur in the Fe-only hydrogenases forms efficiently by the condensation of Fe2(SH)2(CO)6 (1), formaldehyde, and ammonia (as (NH4)2CO3). The resulting Fe2[(SCH2)2NH](CO)6 reacts with Et4NCN to give (Et4N)2[Fe2[(SCH2)2NH](CO)4(CN)2], for which crystallographic characterization confirmed an axial N-H and an elongated C-S bond of 1.858(3) A. Primary amines RNH2 (R = Ph, t-Bu) also participate in the condensation reaction, and Fe3S2(CO)9 can be employed in place of 1. Mechanistically, the Fe2[(SCH2)2NH] moiety is shown to arise via two pathways: (i) via the intermediacy of Fe2[(SCH2OH)2](CO)6, which was detected and shown to react with amines, and (ii) via the reaction of 1 with cyclic imines (CH2)3(NR)3 (R = Ph, Me). The reaction of 1 with (CH2)6N4 (hexamethylenetetramine) gives Fe2[(SCH2)2NH](CO)6. Trace amounts of Fe2[(SCH2)2N-t-Bu](CO)6 arise via the reaction of aqueous FeSO4, formaldehyde, NaSH, and t-BuNH2 under an atmosphere of CO.
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign, 601 South Goodwin Avenue, Urbana, Illinois 61801, USA.
authors.forename: Hongxiang
authors.initials: H
authors.lastname: Li
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Rauchfuss
mesh_terms: D000588:Amines / Q000737:chemistry* / Q000378:metabolism; D001372:Aza Compounds / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism; D018360:Crystallography, X-Ray; D006864:Hydrogenase / Q000737:chemistry / Q000378:metabolism*; D054354:Iron Carbonyl Compounds; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000378:metabolism*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry* / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism; D013440:Sulfides / Q000737:chemistry* / Q000378:metabolism
chemical_list: D000588:Amines; D001372:Aza Compounds; D007506:Iron-Sulfur Proteins; D009942:Organometallic Compounds; D013438:Sulfhydryl Compounds; D013440:Sulfides; D054354:Iron Carbonyl Compounds; C118830:iron hydrogenase; D006864:Hydrogenase