Vanadium complexes ammonia

Top row the three components of the Yandulov-Schrock cycle for catalytic dinitrogen reduction. Left the catalyst with the substrate Nj coordinated to Mo (Ar refers to the aryl substituent drawn in detail for one of the nitrogens). Centre the reductant bis(pentamethylcyclopentadienyl)chromium, CpjCr. Right the proton source 2,6-lutidinium borate. Bottom row vanadium complexes with intermediates of nitrogen reduction activated dinitrogen or diazenido(2—) (46a), imide (46b) and ammonia (46c). 

Dinuclear vanadium complexes with bridging diazenido(2—). The ligands are 2,6-bis(l-iminoethyl)pyridine (53)h h mesityl(l—) (54),h l 2-dimethylaminophenyl(l—) and pyridine (55),h l tolane, trimethylphosphine and dimethylamino-Cp(l—) (56),and benzamidinate(l —) (57).P 1 The complexes 54 and 55, containing (r-aUcyls, produce ammonia and hydrazine on protonation. 

Guha AK, Phukan AK. Why vanadium complexes perform poorly in comparison to related molybdenum complexes in the catalytic reduction of dinitrogen to ammonia (Schrock cycle) a theoretical study. Inorg Chem. 2011 50 8826-8833. 

The chelating ion-exchange resins Chelex-100 and Permutit S 1005 completely retain vanadium [Sc, Ni, Cu, Zn, Y, Mo, Ag, Cd, In, rare earths, W, Re (90%), Pb, Bi, and Th] from sea water. Manganese is retained quantitatively only by the Chelex resin. Vanadium (Mo, W, Re) is removed from the resins with 4N ammonia, the other metals with 2 N mineral acids 56). Both resins consist of a cross-linked polystyrene matrix with iminodiacetic acid [—CH2—N(CH2COOH)2] functional groups. Alkali and alkaline earth metals do not form chelates with iminodiacetic acid except at very high pH, whereas many transition metal ions form 1 1 complexes. 

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