Formation of Bridging Nitride Versus Terminal Oxovanadium Promoted by a Vanadium(II) Macrocyclic Complex

The reaction of [VCl2(tmeda)2] with the tetralithium salt of octaethylporphyrinogen (oepg)[Li(thf)]4 initially yielded a monomeric VII complex [(oepg)‐VLi4Cl2(thf)4] (1). Treatment of this species with tetramethylethylenediamine afforded a mixture from which [(oepg)‐V(thf)2][Li(tmeda)2].0.5 toluene (2 a) (or 2 b when ethyl is replaced by nPr) and the unprecedented nitrido‐bridged dimeric species [{oepg)V}2(μ‐N)(μ‐Li) 4]‐[Li(tmeda)2] (3) were isolated and characterized. The bridging nitrogen atom probably originated from the cleavage of dinitrogen, since the same reaction carried out under exclusion of N2 gave [(oepg)VO]‐[Li(tmeda)]2 (4), where the oxo atom probably originated from deoxygenation of THF. The connectivity of 1, 2 b, 3, and 4 was demonstrated by X‐ray analysis. Is dinitrogen the source of the nitride in the complex obtained during the reaction of a VII porphyrinogen derivative with TMEDA? This reaction, shown below on the right, formed a previously unknown dinuclear complex in which the nitride atom is encapsulated in a V2Li4 octahedron. The same reactants under an argon atmosphere (below left) yielded the corresponding mononuclear oxovanadium species.