Interaction of nitric oxide with paramagnetic and diamagnetic alkyls of titanium, zirconium, vanadium, niobium, and tantalum

Abstract

An earlier observation that there is a profound difference in the way paramagnetic and diamagnetic alkyl compounds of transition metals react with nitric oxide is extended. The reaction of NO with bis(η⁵-cyclopentadienyl)-dimethylniobium(IV), d¹, can be followed by nuclear magnetic resonance spectra and intermediates detected. The final product of the reaction is bis(η⁵-cyclopentadienyl)methyloxoniobium(V), which with excess of NO, gives the N-methyl-N-nitrosohydroxylaminato-complex Nb(η-C₅H₅)₂(O)[ON(Me)NO]. An intermediate niobioaziridine collapses with methylnitrene transfer to give azomethane, and in the presence of styrene, an aziridine. Tetrakis(trimethylsilylmethyl)vanadium(IV) gives with NO the previously known VO(CH₂SiMe₃)₃ while the titanium(III), d¹, compounds Ti(η-C₅H₅)₂R(R = Ph or CH₂Ph) lose both cyclopentadienyl and aryl or benzyl groups to give a trimeric species Ti₃(η-C₅H₅)₃O₄(NO) that has oxo-bridges and a bent Ti–NO group. The diamagnetic alkyls of titanium and zirconium, TiR₄, TiR₃Cl, TiR₂Cl₂, ZrR₄, and ZrR₂Cl₂(R = CH₂SiMe₃ or CH₂CMe₃) and NO give N-alkyl-N-nitrosohydroxylaminato-complexes. The titanium compounds are six-co-ordinate with unidentate and bidentate ON(R)NO groups, while the zirconium compounds are eight-co-ordinate with chelate groups only. The pentamethyls MMe₅(M = Nb or Ta) and NO give NbMe₂[ON(Me)NO]₃ and {TaMe₃[ON(Me)NO]₂}₂ respectively.