Electrochemical Cleavage of NN Bonds at a Mo2(μ-SMe)3 Site Relevant to the Biological Reduction of Dinitrogen at a Bimetallic Sulfur Centre
✍ Scribed by Nathalie Le Grand; Kenneth W. Muir; François Y. Pétillon; Christopher J. Pickett; Philippe Schollhammer; Jean Talarmin
- Publisher
- John Wiley and Sons
- Year
- 2002
- Tongue
- English
- Weight
- 247 KB
- Volume
- 8
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
The reduction of diazene complexes Mo(2)Cp(2)(mu-SMe)(3)(mu-eta(2)-H-N=N-R) (R=Ph (3 a); Me (3 b)) and of the hydrazido(2-) derivative Mo(2)Cp(2)(mu-SMe)(3)[mu-eta(1)-N=N(Me)H] (1 b) has been studied by cyclic voltammetry, controlled-potential electrolysis, and coulometry in THF. The electrochemical reduction of 3 a in the presence of acid leads to cleavage of the N=N bond and produces aniline and either the amido complex [Mo(2)Cp(2)(mu-SMe)(3)(mu-NH(2))] 4 or the ammine complex [Mo(2)Cp(2)(mu-SMe)(3)(NH(3))(X)] 5, depending on the initial concentration of acid (HX=HTsO or CF(3)CO(2)H). The N=N bond of the methyldiazene analogue 3 b is not cleaved under the same conditions. The ability of 3 a but not 3 b 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 1 b 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 [Mo(2)Cp(2)(mu-SMe)(3)(mu-eta(1)-N=N-Me)]. Formation of the last of these complexes indicates that two mechanisms (N=N bond cleavage and possibly H(2) production) are operative. A pathway for the reduction of N(2) at a dinuclear site of FeMoco is proposed on the basis of these results.