Catalytic Reduction of cis-Dimethyldiazene by the [MoFe₃S₄]³⁺ Clusters. The Four-Electron Reduction of a NN Bond by a Nitrogenase-Relevant Cluster and Implications for the Function of Nitrogenase

Abstract

The catalytic reduction of cis-dimethyldiazene by the (Et4N)2[(Cl4-cat)(CH3CN)MoFe3S4Cl3] cluster (Cl4-cat = tetrachlorocatecholate) is reported. Unlike the reduction of cis-dimethyldiazene by the Fe/Mo/S center of nitrogenase, which yields methylamine, ammonia, and methane (the latter from the reduction of the C−N bond), the reduction of cis-dimethyldiazene by the synthetic cluster yields exclusively methylamine. In separate experiments, it was shown that the C−N bond of methylamine is not reduced by the [MoFe3S4]3+ core, perhaps accounting for the differences observed between the biological and abiological systems. 1,2-Dimethylhydrazine, a possible partially reduced intermediate in the reduction of cis-dimethyldiazene, was also shown to be reduced to methylamine. Interaction of methylamine with the Mo atom of the cubane was confirmed through the synthesis and structural characterization of (Et4N)2[(Cl4-cat)(CH3NH2)MoFe3S4Cl3]. Phosphine inhibition studies strongly suggest that the Mo atom of the [MoFe3S4]3+ core, which has a Mo coordination environment very similar to that in nitrogenase, is responsible for the binding and activation of cis-dimethyldiazene. The reduction of a NN bond exclusively at the heterometal site of a nitrogenase-relevant synthetic compound may have implications regarding the function of the nitrogenase Fe/Mo/S center, particularly in the latter stages of dinitrogen reduction.

Determination of ligand binding constants for the iron-molybdenum cofactor of nitrogenase: monomers, multimers, and cooperative behavior

“…The data as originally published and cast as a FeMoco(sr) dodecamer, i.e., as for [FeMoco(sr)] 12 , are shown in Fig. 7 along with the dodecamer model ®t to the data.…”

“…Ever since the iron-molybdenum cofactor (FeMoco) of Azotobacter vinelandii and Klebsiella pneumoniae nitrogenase was isolated [1], interest in the chemistry [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16], electronic structure [17,18,19,20,21,22,23,24,25], and rational synthesis [26,27,28,29,30,31,32,33,34] of this heterometal cluster has been intense. After publication of the solution to the crystal structure of the nitrogenase enzyme [35,36], this interest became structurally more explicit [13,37,38,39,40].…”

Diazene (HNNH) Is a Substrate for Nitrogenase: Insights into the Pathway of N2 Reduction

“…While a FeMo-cofactor bound diazene seems likely as an early intermediate in the pathway, assessment of the interactions of diazene with nitrogenase have proven challenging because of the short half-life of diazene in aqueous solutions. McKenna and coworkers (29,30) were able to demonstrate that dimethyldiazene (H 3 C-N=N-CH 3 ) and diazirine (cyclic methyldiazene) are substrates for nitrogenase. More recently it was shown that methyldiazene (HN=N-CH 3 ) could be used as a substrate for nitrogenase (27).…”

Contents

“…4-5-6, 2008 Crvstallographic and Structural Analysis Of Iron Helerometallic Compounds There are in total only three compounds [150,199,342] distortion being examples of distortion isomerism. [32] There are, however, several cases where there are crystallographically different moieties in a unit cell [9,11,15,30,31,39,50,53,56,71,72,106,124,151,173,190,198,210,235,245,248,261,267,274,288,299,300,317,340,342]. There are even three crystallographically independent units in {(CO) 9 Fe 2 Ru 2^4 -CHC(CH 2 )CHCCH 2 ]cp 2 } .…”

“…Brought to you by | New York University Bobst Library Technical Services Authenticated Download Date | 7/8/15 3:37 AM of (r| 6 -l,3,5-tris((r| 5 -cyclopentadienyl)-dicarbonyliron)benzene)-tricarbonylchromium) [45] There are in total 23 generally black compounds containing an Fe 3 Mo cluster [46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61] ( Table 2). Two of them [46] have adopted a distorted Roussin-like cuboidal structure with MoFe 3 S 3 cores.…”