Stepwise Reduction of Dinitrogen Occurring on a Divanadium Model Compound: A Synthetic, Structural, Magnetic, Electrochemical, and Theoretical Investigation on the [V=N=N=V]n+
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- 作者：Richard Ferguson ; Euro Solari ; Carlo Floriani ; Domenico Osella ; Mauro Ravera ; Nazzareno Re ; Angiola Chiesi-Villa ; and Corrado Rizzoli
- 刊名：Journal of the American Chemical Society
- 出版年：1997
- 出版时间：October 22, 1997
- 年：1997
- 卷：119
- 期：42
- 页码：10104 - 10115
- 全文大小：405K
- 年卷期：v.119,no.42(October 22, 1997)
- ISSN：1520-5126
文摘
This report details an extensive investigation onvanadium-dinitrogen complexes containing the [V(
-N2)V]n+ skeleton witha variable oxidation state of the metal and reduction degree ofdinitrogen, n varying from 6
5 4. This skeleton can be associated to alkali cations inion-separated or ion-pair tight forms. The reactionof [(Mes)3V(thf)], 1 [Mes =2,4,6-Me3C6H2], with Lewis acids[AlPh3, B(C6F5)3]removed the THF molecule leadingunder nitrogen to the formation of the diamagnetic complex[(Mes)3V(-N2)V(Mes)3],4. The reaction of 1 withN2also occurs under reducing conditions using Na or K metals. Assupported by the electrochemical study, the preliminarystage is in both cases the formation of the vanadium(II)desolvated form [V(Mes)3]-, 5.The reaction of 5 with N2in the case of potassium and in the presence of 1 leads tothe compound{[(Mes)3V(-N2)V(Mes)3]-[K(digly)3]+},11, which, depending on the reaction conditions, undergoes afurther reduction to[{K(digly)3(-Mes)2(Mes)V}2(-N2)], 12 [digly = diethylene glycol dimethylether]. Similarly, the reduction of 1 with sodiumgave, depending onthe workup mode,{[(Mes)3V(-N2)V(Mes)3]2-[Na(digly)2]+2},13, or{[(Mes)3V(-N2)(-Na)V(Mes)3]-[Na(digly)2]+},14, both containing the dianion[(Mes)3V(-N2)V(Mes)3]2-,8. Complex 4 releases upon protonationexclusivelyN2, while complexes 11-14 releaseN2, N2H4, and NH3 inamounts depending on the degree of reduction of thedinitrogen and the structure of the complex. The electrochemicalreduction of 1 shed light on the intermediateformation of 5 and its conversion to 8, which wasoxidized to the monoanion[(Mes)3V(-N2)V(Mes)3]-,7 (whichis the precursor of 8 in the chemical reduction). Themagnetic studies coupled with the theoretical interpretationarein agreement with the presence of a d2-d2couple in 4, a d1-d1 in12-14, and a d1-d0 in11. This, along with thestructural studies on 11-14, suggest acumulenic structure[V=N=N=V]+n [n= 5, 4] for 11-14.
-N2)V]n+ skeleton witha variable oxidation state of the metal and reduction degree ofdinitrogen, n varying from 6 5 4. This skeleton can be associated to alkali cations inion-separated or ion-pair tight forms. The reactionof [(Mes)3V(thf)], 1 [Mes =2,4,6-Me3C6H2], with Lewis acids[AlPh3, B(C6F5)3]removed the THF molecule leadingunder nitrogen to the formation of the diamagnetic complex[(Mes)3V(-N2)V(Mes)3],4. The reaction of 1 withN2also occurs under reducing conditions using Na or K metals. Assupported by the electrochemical study, the preliminarystage is in both cases the formation of the vanadium(II)desolvated form [V(Mes)3]-, 5.The reaction of 5 with N2in the case of potassium and in the presence of 1 leads tothe compound{[(Mes)3V(-N2)V(Mes)3]-[K(digly)3]+},11, which, depending on the reaction conditions, undergoes afurther reduction to[{K(digly)3(-Mes)2(Mes)V}2(-N2)], 12 [digly = diethylene glycol dimethylether]. Similarly, the reduction of 1 with sodiumgave, depending onthe workup mode,{[(Mes)3V(-N2)V(Mes)3]2-[Na(digly)2]+2},13, or{[(Mes)3V(-N2)(-Na)V(Mes)3]-[Na(digly)2]+},14, both containing the dianion[(Mes)3V(-N2)V(Mes)3]2-,8. Complex 4 releases upon protonationexclusivelyN2, while complexes 11-14 releaseN2, N2H4, and NH3 inamounts depending on the degree of reduction of thedinitrogen and the structure of the complex. The electrochemicalreduction of 1 shed light on the intermediateformation of 5 and its conversion to 8, which wasoxidized to the monoanion[(Mes)3V(-N2)V(Mes)3]-,7 (whichis the precursor of 8 in the chemical reduction). Themagnetic studies coupled with the theoretical interpretationarein agreement with the presence of a d2-d2couple in 4, a d1-d1 in12-14, and a d1-d0 in11. This, along with thestructural studies on 11-14, suggest acumulenic structure[V=N=N=V]+n [n= 5, 4] for 11-14.