Elusive Terminal Copper Arylnitrene Intermediates.

We report herein three new modes of reactivity between arylazides N Ar with a bulky copper(I) β-diketiminate. Addition of N Ar (Ar =2,4,6-X C H ; X=Cl or Me) to [ Pr NN]Cu(NCMe) results in triazenido complexes from azide attack on the β-diketiminato backbone. Reaction of [ Pr NN]Cu(NCMe) with bulkier azides N Ar leads to terminal nitrenes [ Pr 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- Pr C H ) or undergo nitrile insertion to give diazametallocyclobutene 8 (Ar=4-Ph-2,6-iPr C H ). Importantly, reactivity studies reveal both 4 and 8 to be "masked" forms of the terminal nitrenes [ Pr NN]Cu=NAr that undergo nitrene group transfer to PMe , BuNC, and even into a benzylic sp C-H bond of ethylbenzene.