Elusive Terminal Copper Arylnitrene Intermediates

We report herein three new modes of reactivity between arylazides N3Ar with a bulky copper(I) β-diketiminate. Addition of N3ArX3 (ArX3=2,4,6-X3C6H2; X=Cl or Me) to [iPr2NN]Cu(NCMe) results in triazenido complexes from azide attack on the β-diketiminato backbone. Reaction of [iPr2NN]Cu(NCMe) with bulkier azides N3Ar leads to terminal nitrenes [iPr2NN]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-iPr2C6H3) or undergo nitrile insertion to give diazametallocyclobutene 8 (Ar=4-Ph-2,6-iPr2C6H2). Importantly, reactivity studies reveal both 4 and 8 to be “masked” forms of the terminal nitrenes [iPr2NN]Cu=NAr that undergo nitrene group transfer to PMe3, tBuNC, and even into a benzylic sp3 C−H bond of ethylbenzene.