Reassessment of N2 activation by low-valent Ti-amide complexes: a remarkable side-on bridged bis-N2 adduct is actually an arene adduct

Abstract

The complex {(TMEDA)₂Li}{[Ti(N(TMS)₂)₂]₂(μ-η²:η²-N₂)₂} (5-Li) is the only transition metal N₂ complex ever reported with two side-on N₂ adducts. In this report, the similarity of 5-Li to a new inverse sandwich toluene adduct {(PhMe)K}{[Ti(N(TMS)₂)₂]₂(μ-PhMe)} (6-K) necessitated a re-examination of the structure of 5-Li. Through a reassessment of the original disordered crystal data of 5-Li and new independent syntheses brought about through revisitation of the original reaction conditions, 5-Li has been re-assigned as an inverse sandwich toluene adduct, {(TMEDA)₂Li}{[Ti(N(TMS)₂)₂]₂(μ-PhMe)} (6-Li). The original crystal data could be fitted almost equally well to structural solutions as either 5-Li or 6-Li, and this study highlights the importance of a holistic examination of modeled data and the need for secondary/complementary analytical methods in paramagnetic inorganic syntheses, especially when presenting unique and unexpected results. In addition, further examination of reduction reactions of Ti[N(TMS)₂]₃ and [(TMS)₂N]₂TiCl(THF) in the presence of KC₈ revealed rich solvent- and counterion-dependent chemistry, including several degrees of N₂ activation (bridging nitride complexes, terminal bridging N₂ complexes) as well as ligand C–H activation.