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Electrochemical cleavage of N=N bonds at a Mo2(μ-SMe)3 site relevant to the biological reduction of dinitrogen at a bimetallic sulfur centre

Abstract : The reduction of diazene complexes [Mo2Cp2(μ-SMe)3(μ- η2-H-N=N-R)]+(R=Ph (3a); Me (3b)) and of the hydrazido(2 -) derivative [Mo2Cp2(μ-SMe)3_μ- η1-N=N(Me)H_]+ (1b) has been studied by cyclic voltammetry, controlled-potential electrolysis, and coulometry in THF. The electrochemical reduction of 3a in the presence of acid leads to cleavage of the N=N bond and produces aniline and either the amido complex [Mo2Cp2(μ-SMe)3-(μ-NH2)] 4 or the ammine complex [Mo2Cp2(μ-SMe)3(NH3)(X)] 5, depending on the initial concentration of acid (HX=HTsO or CF3CO2H). The N=N bond of the methyldiazene analogue 3b is not cleaved under the same conditions. The ability of 3a but not 3b to undergo reductive cleavage of the N=N bond is attributed to electronic control of the strength of the Mo-N(R) bond by the R group. The electrochemical reduction of the methylhydrazido(2 -) compound 1b in the presence of HX also results in cleavage of the N=N bond, with formation of methylamine, 4 (or 5) and the methyldiazenido complex [Mo2Cp2(μ-SMe)3(μ- η1-N=N-Me)]. Formation of the last of these complexes indicates that two mechanisms (N=N bond cleavage and possibly H2 production) are operative. A pathway for the reduction of N2 at a dinuclear site of FeMoco is proposed on the basis of these results.
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https://hal.univ-brest.fr/hal-01771333
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Submitted on : Thursday, April 19, 2018 - 2:47:53 PM
Last modification on : Thursday, October 3, 2019 - 8:50:02 AM

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N.L. Le Grand, K.W. Muir, François Pétillon, C.J. Pickett, Philippe Schollhammer, et al.. Electrochemical cleavage of N=N bonds at a Mo2(μ-SMe)3 site relevant to the biological reduction of dinitrogen at a bimetallic sulfur centre. Chemistry - A European Journal, Wiley-VCH Verlag, 2002, 8, pp.3115--3127. ⟨10.1002/1521-3765(20020715)8:14<3115::AID-CHEM3115>3.0.CO;2-Z⟩. ⟨hal-01771333⟩

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