Dinitrogen complexes niobium

Reduction of the cyclometallated Nb(V) species [(Cy2N)2NbCl(T] -CyN= CeHio)] with NaBFIEts affords [ (Cy2N)2Nb 2(p-ri T -N2)] (60), which was the first niobium dinitrogen complex formed by direct N2 activation. The long N—N bond distance of 1.34(1) A is consistent with a formal (N2) unit. 

Fryzuk MD, Kozak CM, Bowdridge MR, Patrick BO, Rettig SJ. Nitride formation by thermolysis of a kinetically stable niobium dinitrogen complex. J Am Chem Soc. 2002 124 8389-8397. 

Bemo, P. and Gambarotta, S., Formation of a metalaaziridine ring and dinitrogen fixation promoted by a niobium amide complex. Organometallics, 14 (1995) 2159-2161. 

An impure dinitrogen complex of niobium has been reported by Leigh et Complex 4 (see Table 1) is formulated as a dinuclear complex with a bridging dinitrogen. Treatment with acid yields no ammonia, but ca. 20% of the nitrogen is converted to hydrazine, the remainder being evolved as N2. 

Akagi P, Suzuki S, Ishida Y, Hatanaka T, Matsuo T, Kawaguchi H. Reactions of a niobium nitride complex prepared from dinitrogen synthesis of imide and ureate complexes and ammonia formation. Eur J Inorg Chem. 2013 3930—3936. 

Scheme 5.11 Cleavage of dinitrogen in the synthesis of niobium nitride complex.

Niobium, tris(diethyldilhiocarbamato)oxy-stereochemistry, 1,82 structure, 1, 83 Niobium, tris(oxa ato)oxy-stereochcmistry, 1, 82 Niobium, tris(phcnylcncdirhio)-structure, 1, 63 Niobium alanate, 3, 685 Niobium complexes alkyl alkoxy reactions, 2, 358 amides, 2,164 properties, 2, 168 synthesis, 2, 165 applications, 6,1014 carbamicacid, 2, 450 clusters, 3, 672,673,675 hexamethylbenzene ligands, 3, 669 cyanides synthesis, 2, 9 p-dinitrogen, 3, 418 fluoro... 

Niobium and tantalum belong to the metals that are able to bind dinitrogen. The development of this area was first due to Schrock and coworkers, who in 1982 could obtain stable tantalum /X-N2 compounds in high yields by reducing Alkylidene complexes under dinitrogen at normal pressure.This route can be circumvented in a single pot synthesis by reacting the pentahalides with sUylated hydrazines (equation 12). 

Scheme 4 Mechanism of the production of bridging dinitrogen in niobium and tantalum dithiocarbamate complexes (R2dtc, etc. Omitted for clarity)...

A few derivatives of oxyanions have also been prepared protactinium (V) forms hexanitrato complexes, Pa(N03)e , by reaction of the hexachloro complex with dinitrogen pentoxide, in contrast to niobium and tantalum which, under similar conditions, yield only tetranitrato complexes, M0(N03)4 (35). Neptunium (V) nitrates, NPO2NO3 and Np0(N03)3 have also been reported 71). Protactinium (V) sulfato-and selenato complex acids, H3PaO( 804)3 and H3Pa0(Se04)3, have been obtained from aqueous solution (13), but no fully sulfated or sele-nated species have been recorded. 

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). 

Kinetics and mechanisms of hydrazine-forming reactions, involving coupled redox and substitution processes, from dinitrogen-bridged dinuclear diethyldithiocarbamate complexes of niobium and tantalum have been reported and discussed. ... 

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