Dinitrogen binding and electrochemistry in complexes of molybdenum and tungsten

Abstract

The preparation of a series of complexes [M(N₂)₂{(p-XC₆H₄)₂PCH₂CH₂P(C₆H₄X-p)₂}₂](M = Mo or W) is described. The variation of oxidation potential with phosphine substituents suggests that the electronic structures involve through-metal conjugation between the phosphine phosphorus and the dinitrogen, which contributes to the strength of the metal–dinitrogen bond. Electron-donating substituents on the phosphine make the compounds easier to oxidise. Studies of the rate of replacement of dinitrogen by benzonitrile show that electron-donating substituents also increase the metal–dinitrogen bond lability.