Reductive N–N bond cleavage and coupling of organic azides mediated by chromium(I) and vanadium(I) β-diketiminate

Reactions of organic azides RN3 with two univalent inverted-sandwich complexes (μ-η6:η6-C6H5CH3)[M(Nacnac)]2 (M = Cr (1) and V (2); Nacnac = HC(C(Me)NC6H3iPr2)2) have been investigated. Where R = p-tolyl, reaction with 1 results in reductive N2 elimination and the formation of a diimido product Cr(NR)2(Nacnac) and a cycloaddition tetrazene product Cr[N(R)NNN(R)](Nacnac), which can be converted to Cr(NR)2(Nacnac) upon thermolysis. However, reaction of 1 with Me3SiN3 does not produce a diimido complex, but a monomeric three-coordinate amido product Cr[N(SiMe3)2](Nacnac) and an azide-bridged dinuclear compound [Cr(μ-N3)(Nacnac)]2. On the other hand, where R = p-tolyl, 1-adamantyl, or SiMe3, reaction with the more reducing 2 gives solely a diimido product V(NR)2(Nacnac). The symmetric diimido complex V(NSiMe3)2(Nacnac) (10) can be converted to an asymmetric diimido complex V(NSiMe3)(N-2,6-C6H3iPr2)[Me3SiNC(Me)C(H)C(Me)N(2,6-C6H3iPr2)] (11) upon heating.