Ruthenium complexes dinitrogen activation

Increasing the number of electrons reduces the activation of N2, because the electrons occupy the orbitals which are bonding with respect to the NN bond, and actually stabilize it. In agreement with this prediction dinitrogen is sufficiently activated to be reduced by protonation by dinuclear complexes of titanium(II), zirco-nium(Il), niobium(III), tantalum(III), molybdenum(IV), and tungsten(IV), whereas it is not reduced by protonation by certain d -d complexes, such as those of molybdenum(O), ruthenium(II), or rhodium(I). Apparently dinuclear complexes M-N=N-M in which M has the d electronic configuration can be intermediates in dinitrogen reduction in protic media, particularly if they represent part of polynuclear complexes (vide infra). 

The reaction is insensitive to whether the atmosphere used is dinitrogen or carbon monoxide. The iron complex Fe3(PPh3)2 proved to be much less. active than its ruthenium analogue in this reaction. Analyses o-f the gas evolved during the catalytic reactions conducted under dinitrogen have shown the -formation o-f carbon dioxide, but its quantity was less than calculated on the basis o-f the PhNO converted. On the other hand, in protic media the reaction could proceed via the proton trans-fer -from the solvent to n i trosobenzene, with the intermediate formation o-f hydroxyl ami ne s... 

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