Vanadium(‐I) Dinitrogen Complexes with N₂ Coordinated End‐on: Functional Models for the “Alternative Nitrogenase”

Abstract

A sensitive probe for the formation of the anionic N2‐complexes 1 and 2 upon reaction of [VCl3(thf)3] with N2, dmpe, and Na is their centeral metal. Thus, the 51V‐NMR signal of the trans‐complex 1 is a quintet at δ = − 1123. If the reduction is carried out under 15N2, the individual multiplet components additionally split to triplets, a direct indication of the incorporation of nitrogen in the complex. dmpe = dimethylphosphinoethane.

Nitride Formation by Thermolysis of a Kinetically Stable Niobium Dinitrogen Complex

“…Our continued interest in the synthesis of dinitrogen compounds and the availability of the Nb(III) starting complex [P 2 N 2 ]NbCl ( 1 ) 16 prompted us to examine its ability to bind N 2 under reducing conditions. Within group 5, there are a number of dinitrogen complexes of vanadium and tantalum that have been reported; ,− however, those of niobium continue to be rare. ,− Reduction of [P 2 N 2 ]NbCl ( 1 ) by KC 8 in toluene under 1 atm of N 2 for 48 h allows isolation of a dark brown paramagnetic solid in 85% yield that has been characterized as ([P 2 N 2 ]Nb) 2 (μ-N 2 ) ( 2 ). Varying the reaction conditions by changing the solvent to THF, increasing the pressure of N 2 to 4 atm, or performing the reaction at temperatures from −78 to +65 °C did not appear to affect the yield.…”

Exploring the role of pendant amines in transition metal complexes for the reduction of N2 to hydrazine and ammonia

“…In addition to the group 6 complexes described above, recent efforts investigated the coordination chemistry of organometallic vanadium complexes containing P R N R′ P R , and P R 2N R′ 2 ligands. Vanadium complexes bearing traditional phosphine ligands have been shown to coordinate N2 [94] and in some cases produce ammonia and hydrazine upon treatment with acid [95][96][97]. These results motivated our studies to explore vanadium complexes containing pendant amines.…”

Synthesis of Vanadium(III), -(IV), and -(V) Complexes That Contain the Pentafluorophenyl-Substituted Triamidoamine Ligand [(C6F5NCH2CH2)3N]3-

“…A variety of vanadium complexes that contain triamidoamine ligands of the type [(RNCH 2 CH 2 ) 3 N] 3- (where R is a trialkylsilyl group) have been reported. − Initially we were surprised that the “trigonal monopyramidal” versions 3 do not bind dinitrogen for several reasons. First, a variety of vanadium dinitrogen complexes are known, some of which contain largely or exclusively amido ligands. − Second, the coordination site in [(RNCH 2 CH 2 ) 3 N]V complexes contains two orthogonal π orbitals and a σ orbital pointing along the z axis, a circumstance that would seem to be optimal for binding dinitrogen in an “end-on” fashion. Third, we recently reported several triamidoamine complexes of molybdenum, including two that contain dinitrogen .…”