Reactions of a Niobium Nitride Complex Prepared from Dinitrogen: Synthesis of Imide and Ureate Complexes and Ammonia Formation

A nitride complex [K(thf)(2)](2)[{(O-3)Nb}(2)(-N)(2)] (2), prepared from [K(DME)](2)[{(O-3)Nb}(2)(-H)(4)] (1) and N-2, was protonated with 2,6-lutidinium chloride to yield ammonia and [(O-3)NbCl3](-) (3), where H-3[O-3] = tris(3,5-di-tert-butyl-2-hydroxy phenyl)methane. The reaction of 3 with KBHEt3 regenerated [K(DME)](2)[{(O-3)Nb}(2)(-H)(4)] (1), thereby completing a synthetic cycle for the conversion of N-2 to NH3. Alkylation of 2 with methyl iodide led to formation of [K(thf)][{(O-3)Nb}(2)(-N)(-NMe)] (4) and [{(O-3)Nb}(2)(-NMe)(2)] (5). Treatment of 5 with pyridine afforded a terminal imide complex [(O-3)Nb=NMe(py)(2)] (6). The imide monomer 6 reacted with CO2 to give [(O-3)Nb{(MeN)(2)CO}(py)] (7) and [{(O-3)Nb}(2)(-O)(2)] (8) in a 2:1 ratio, while the reaction of 6 with p-TolNCO gave an asymmetric ureate complex [(O-3)Nb{p-TolNC(O)NMe}(py)] (9).