Structural Characterization and Reactivity Properties of a New Class of Fe/Mo/S Double Cubanes with Mo-Bound S-.mu.2-.eta.1,O-.eta.1 Mercapto Carboxylate Ligands. New Catalysts for the Reduction of Hydrazine to Ammonia and Implications Regarding the Function of Nitrogenase

Demadis, Konstantinos D.; Coucouvanis, D.

doi:10.1021/ic00118a013

Cited by 38 publications

(10 citation statements)

References 4 publications

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“…The protocol used in sample collection and treatment prior to analysis is identical to the one described in ref. [35] c The average of n independent experiments is reported where n is the number in parentheses The results of the catalytic studies will be summarized with reference to the questions raised previously regarding the function of nitrogenase.…”

Section: Introductionmentioning

confidence: 99%

Functional analogs for the reduction of certain nitrogenase substrates. Are multiple sites within the Fe/Mo/S active center involved in the 6e– reduction of N2?

Coucouvanis

1996

J Biol Inorg Chem

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Reactivity studies of clusters that contain the MFe 3 S 4 cores (M p Mo, V) with catecholate, multicarboxylate (or DMF) ligands coordinated to the Mo (or V) atoms, and Cl ligands coordinated to the Fe atoms have been carried out. These studies show the M/Fe/S single cubane clusters to be effective catalysts in the reduction of nitrogenase substrates such as hydrazine, acetylene and protons to give ammonia, ethylene and dihydrogen respectively. The same molecules do not activate or catalyze the reduction of dinitrogen. The results indicate that the observed catalyses are occurring at the Mo (V) sites by a process that, in the case of hydrazine, involves substrate protonation prior to reduction. The facile catalytic reduction of hydrazine by clusters that contain coordinatively saturated polycarboxylate-bound Mo atoms is rationalized in terms of a possible protonation/proton delivery function of the coordinated polycarboxylate ligands. The reactivity characteristics of the M/Fe/S clusters (structurally quite similar to the nitrogenase cofactor) have led to the suggestion that the Mo (V) atoms may be involved in the reduction of hydrazine in the later stages of dinitrogen reduction.

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Section: Introductionmentioning

confidence: 99%

Functional analogs for the reduction of certain nitrogenase substrates. Are multiple sites within the Fe/Mo/S active center involved in the 6e– reduction of N2?

Coucouvanis

1996

J Biol Inorg Chem

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“…Whilst such a bonding mode has been found in some dinuclear coordination compounds of Mo,13a Re,13b Fe,13c Ru,13d–13f Rh,13g Pt,13h and other metals, this is unprecedented for double‐cubane structures. However, numerous examples of bridging S ligands are found in the [Fe 4 S 4 ] and FeMoS clusters, studied extensively by Holm et al and Coucouvanis et al, including sulfide or disulfide,14a–14c alkyl thiolates,14d,14e and 1,2‐ethane‐dithiolates 14f,14g…”

Section: Methodsmentioning

confidence: 99%

C−S Bond Cleavage and C−C Coupling in Cyclopentadienylchromium Complexes To Give the First Dithiooxamide-Bridged and Doubly Dithiocarbamate-Bridged Double Cubanes: [Cp6Cr8S8{(C(S)NEt2)2}] and [Cp6Cr8S8(S2CNEt2)2]

et al. 2001

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There have been extensive studies on the use of the dithiocarbamate ligand in a variety of bonding modes for stabilizing a wide range of oxidation states in coordination compounds of main-group and transition metals. [1] Although generally unreactive in the majority of its complexes, this ligand can undergo CÀS bond cleavage, a phenomenon first observed in a Mo complex in 1972 and becoming increasingly common in the last two decades. [2] In most cases, the cleaved S atom takes on a distinctly different coordination role in the complex, except where it is abstracted by an S acceptor such as PEt 3 . [2c] For example, the cleaved S atom can assume a bridging mode (M-S-M), [2a,b,f, 3] form an MS bond, [2d,g] or interact with a neighboring ligand (e.g., the MC bond of a coordinated alkyne). [2e] Cleavage of both CÀS bonds of the ligand was reported for reactions with [Ru 3 (CO) 12 ] [2h] and [Mo 2 (m-O 2 CMe) 4 ]. [3] Other reactions of the dithiocarbamate ligand include oxidative addition of a C À S bond to alkynes [4] and coupling reactions with coordinated alkyne, [2c, 5] alkylidene, [6] vinylidene/allenylidene, [7] and cyanide [8] ligands. Most of these studies involved Mo and W complexes, except for a few examples containing Cu, [4d] Nb and Ta, [2g] and Ru. [2h, 7] In the course of our investigations on the reactivity of [{CpCr(CO) 3 } 2 ] (Cp h 5 -C 5 H 5 ) towards the EÀE bonds of organic substrates such as diphenyl dichalcogenides Ph 2 E 2 (E S, Se, Te), [9] and bis(diphenylthiophosphinyl)disulfane [Ph 2 P(S)S] 2 , [10] we studied reactions with tetraalkylthiuram disulfides [R 2 NC(S)S] 2 , and here we report the first organochromium complexes containing dithiocarbamate and dithiooxamide ligands.The instantaneous reaction of [{CpCr(CO) 3 } 2 ] with one molar equivalent of tetraethylthiuram disulfide [Et 2 NC(S)S] 2 in toluene at ambient temperature gave a dark red solution, which upon concentration yielded air-stable deep red crystals of [CpCr(CO) 2 (S 2 CNEt 2 )] (1) in 87 % yield. A similar reaction at 90 8C for 2 h gave a dark brown mixture, from which were obtained, in order of elution from a silica gel column, the following compounds: [{CpCr(CO) 2 } 2 S] (7) as a dark green solid (ca. 1 % yield), (1) (22 % yield), [CpCr(CO) 2 (SCNEt 2 )] (2) as a dark red crystalline solid (11 % yield), [Cp 4 Cr 4 S 4 ] (3) as a dark solid (22 % yield), [Cp 6 Cr 8 S 8 {(C(S)NEt 2 ) 2 }] (4) as a brown solid (6.8 % yield), suggests stable trap site for the hole, the position of which is not far from the acceptor. The slow recombination of the geminate ion pair with the relatively short distance would be related to the trap-site structure or some sorts of reorganizations because of the charge shift in the PVCz film.

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“…One of the clusters employed, [(citrate)MoFe 3 S 4 Cl 3 ] 3− even possessed a citrate ligand bound to the Mo atom . These experiments implicated the heterometal in the catalysis, since clusters with coordinatively saturated V and Mo centers lacked catalytic activity . The hypothesis that N 2 binding or reduction in nitrogenase can occur at the heterometal has been shown to be viable from the pioneering work of Chatt and Schrock and cannot be ruled out.…”

Section: Metallocluster Functionalitymentioning

confidence: 99%

Synthetic Analogues of Nitrogenase Metallocofactors: Challenges and Developments

Sickerman

Tanifuji

et al. 2017

Chemistry A European J

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Nitrogenase is the only known biological system capable of reducing N to NH , which is a critical component of bioavailable nitrogen fixation. Since the discovery of discrete iron-sulfur metalloclusters within the nitrogenase MoFe protein, synthetic inorganic chemists have sought to reproduce the structural features of these clusters in order to understand how they facilitate the binding, activation and hydrogenation of N . Through the decades following the initial identification of these clusters, significant progress has been made to synthetically replicate certain compositional and functional aspects of the biogenic clusters. Although much work remains to generate synthetic iron-sulfur clusters that can reduce N to NH , the insights borne from past and recent developments are discussed in this concept article.

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Structural Characterization and Reactivity Properties of a New Class of Fe/Mo/S Double Cubanes with Mo-Bound S-.mu.2-.eta.1,O-.eta.1 Mercapto Carboxylate Ligands. New Catalysts for the Reduction of Hydrazine to Ammonia and Implications Regarding the Function of Nitrogenase

Cited by 38 publications

References 4 publications

Functional analogs for the reduction of certain nitrogenase substrates. Are multiple sites within the Fe/Mo/S active center involved in the 6e– reduction of N2?

Functional analogs for the reduction of certain nitrogenase substrates. Are multiple sites within the Fe/Mo/S active center involved in the 6e– reduction of N2?

C−S Bond Cleavage and C−C Coupling in Cyclopentadienylchromium Complexes To Give the First Dithiooxamide-Bridged and Doubly Dithiocarbamate-Bridged Double Cubanes: [Cp6Cr8S8{(C(S)NEt2)2}] and [Cp6Cr8S8(S2CNEt2)2]

Synthetic Analogues of Nitrogenase Metallocofactors: Challenges and Developments

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