Organogold(III) metallacyclic chemistry.: Part 3.: Self-assembly of the nonametallic gold(III)-silver(I)-sulfido aggregates [{LAu(μ-S)2AuL}3Ag3X2]+ (L = cycloaurated N,N-dimethylbenzylamine ligand; X = Cl, Br), by thiourea desulfurisation

Reaction of the gold(III) dihalide complexes [{C6H3(CH2NMe2)-2-R-5}AuX2] (R = OMe, H; X = Cl, Br) with N,N'-dimethylthiourea and silver(I) oxide in refluxing dichloromethane gave the novel gold(III) aggregate cations [{[{C6H3(CH2NMe2)-2-R-5}Au(mu-S)](2)}(3)Ag3X2](+), formed from the desulfurisation of the thiourea. The cations consist of three gold sulfide dimers doubly-bridged by three silver(I) cations, which in turn are triply-bridged by two halides. The aggregates have been fully characterised by H-1- and C-13-NMR spectroscopy and electrospray mass spectrometry (ESMS), which showed very strong parent ions that proved remarkably resilient to cone voltage induced fragmentation. Single crystal X-ray structures have been determined for two examples, although the nature of the counter-anion could not be unambiguously determined. The two X-ray studies show that both cis and trans isomers (with respect to the orientation of the N,N-dimethylbenzylamine ligands on either side of the Au2S2 group) form, although only one isomer was isolated in each case. To compare this chemistry with that of platinum(II), cis-[PtCl2(PPh3)(2)] and N,N'-dimethylthiourea were reacted in the presence of silver(I) oxide. Only the expected thiourea dianion complex [Pt{SC(=NMe)NMe}(PPh3)(2)] formed, as observed in previously reported studies. The formation of the gold(III)-sulfido aggregates clearly demonstrates that gold(III) can have remarkably different chemistry to that of platinum(II). Reaction of [{C6H3(CH2NMe2)-2-OMe-5}AuCl2] with N,N'-diphenylselenourea in the presence of silver(I) oxide failed to give analogous selenium aggregates. (C) 1998 Elsevier Science S.A. All rights reserved.