Elusive Terminal Copper Arylnitrene Intermediates.

We report herein three new modes of reactivity between arylazides N3 Ar with a bulky copper(I) β-diketiminate. Addition of N3 ArX3 (ArX3 =2,4,6-X3 C6 H2 ; X=Cl or Me) to [i Pr2 NN]Cu(NCMe) results in triazenido complexes from azide attack on the β-diketiminato backbone. Reaction of [i Pr2 NN]Cu(NCMe) with bulkier azides N3 Ar leads to terminal nitrenes [i Pr2 NN]Cu]=NAr that dimerize via formation of a C-C bond at the arylnitrene p-position to give the dicopper(II) diketimide 4 (Ar=2,6-i Pr2 C6 H3 ) or undergo nitrile insertion to give diazametallocyclobutene 8 (Ar=4-Ph-2,6-iPr2 C6 H2 ). Importantly, reactivity studies reveal both 4 and 8 to be "masked" forms of the terminal nitrenes [i Pr2 NN]Cu=NAr that undergo nitrene group transfer to PMe3 , t BuNC, and even into a benzylic sp3 C-H bond of ethylbenzene.