196710-40-4Relevant academic research and scientific papers
Stepwise reduction of dinitrogen occurring on a divanadium model compound: A synthetic, structural, magnetic, electrochemical, and theoretical investigation on the [V=N=N=N](n+) [n = 4-6] based complexes
Ferguson, Richard,Solari, Euro,Floriani, Carlo,Osella, Domenico,Ravera, Mauro,Re, Nazzareno,Chiesi-Villa, Angiola,Rizzoli, Corrado
, p. 10104 - 10115 (1997)
This report details an extensive investigation on vanadium-dinitrogen complexes containing the [V(μ-N2)V](n+) skeleton with a variable oxidation state of the metal and reduction degree of dinitrogen, n varying from 6 → 5 → 4. This skeleton can be associated to alkali cations in ion-separated or ion-pair tight forms. The reaction of [(Mes)3V(thf)], 1 [Mes = 2,4,6-Me3C6H2], with Lewis acids [AlPh3, B(C6F5)3] removed the THF molecule leading under nitrogen to the formation of the diamagnetic complex [(Mes)3 V (μ-N2) V (Mes)3], 4. The reaction of 1 with N2 also occurs under reducing conditions using Na or K metals. As supported by the electrochemical study, the preliminary stages is in both cases the formation of the vanadium(II) desolvated form [V(mes)3]-, 5. The reaction of 5 with N2 in the case of potassium and in the presence of 1 leads to the compound {[(mes)3V(μ-N2)V(Mes)3]-[K(digly)3]+}, 11, which, depending on the reaction conditions, undergoes a further reduction to [{K(digly)3(μ-Mes)2(Mes)V}2(μ-N2)], 12 [digly = diethylene glycol dimethyl ether]. Similarly, the reduction of 1 with sodium gave, depending on the workup model, {[(Mes)3V(μ-N2)V(Mes)3]2-[Na(digly)2]+2}, 13 or {[(Mes)3V(μ-N2)(μ-N2(μ-Na)V(Mes)3]-[Na(digly)2]+}, 14, both containing the dianion [(Mes)3V(μ-N2)V(Mes)3]2-, 8. Complex 4 release upon protonation exclusively N2, while complexes 11-14 release N2, N2H4, and NH3 in amounts depending on the degree of reduction of the dinitrogen and the structure of the complex. The electrochemical reduction of 1 shed light on the intermediate formation of 5 and its conversion to 8, which was oxidized to the monoanion [(Mes)3V(μ-N2)V(Mes)3]-, 7 (which is the precursor of 8 in the chemical reduction). The magnetic studies coupled with the theoretical interpretation are in agreement with the presence of d2-d2 couple in 4, a d1-d1 in 12-14, and a d1-d0 in 11. This, along with the structural studies on 11-14, suggest a cumulenic structure [V=N=N=V](+n) [n = 5, 4] for 11-14.
