Mononuclear Bis(imino)arylcopper(I) N-Heterocyclic Carbene Complex: Synthesis, Structure, and Reaction with Organic Azide

Mononuclear bis(imino)arylcopper(I) N-heterocyclic carbene compound [(IPM)CuL] {1, L = 2,6-(RN=CH)(2)-4-tBuC(6)H(2), R = 2,6-iPr(2)C(6)H(3), IPM = C[N(iPr)CMe](2)} has been synthesized, structurally characterized, and its reaction with 1-adamantyl azide investigated. The reaction of a less bulky arylcopper(I) compound [(IPM)CuPh] with the azide was also studied. The formation of the corresponding products [(IPM)CuN(1-ad)-NN(L)] (2) and [(IPM)CuN(Ph)NN(1-ad)] (3) (1-ad = 1-adamantyl) reveals an aryl group transfer (L in 2 and Ph in 3) reactivity pattern mediated at Cu-1 with the support of the N-heterocyclic carbene. However, a Cu-N1-ad sigma-bond and a Cu ... N-L weak bond were observed in the structure of 2, significantly different to the bonding in 3 in which a Cu-N-Ph sigma-bond and a Cu ... N1-ad weak bond were indicated. This may suggest an initial N-T (N-T, terminal N atom of the azide) coordination of the azide at the Cu center followed by aryl group transfer to N-T. Complex 2 may undergo further bond rearrangement of the Cu ... N bonds within a pseudo-CuN3 four-membered ring as a result of the large bulk of the ligand L.