One-step formation of cyclometallated Au(III) N,S-heterocyclic carbene: crystallographic analysis.

Gold(I) N,S-heterocyclic carbene AuBr(NSHC) (NSHC = N-allylbenzothiazolin-2-ylidene) (1) with an allyl pendant is oxidised by iodine to give [AuI2(NSHC)2]+[I3]- (2) and a cyclometallated byproduct AuBr2(-C6H4SCNCH2CHCH2Br-C,C) (3). The latter can be prepared directly from bromination of 1. Similar reaction with the crotyl (but-2-en-1-yl) derivative AuBr(NSHC) (NSHC = N-crotylbenzothiazolin-2-ylidene) (4) gives an oxidative addition product AuBr3(C6H4SCNCH2CHCHCH3) (5). X-Ray single-crystal crystallographic analysis of 3 reveals a 5-membered cyclometallated ring in a sq planar metal that gives two types of AuIII-C bonds. Similar structural analysis has also been carried out in 1, 2 and 5.