Syntheses , structures and theoretical investigations of [ Au 10 S 2 ( PPh 2 ) 2 ( dppma 2 ) 4 - ( dppma 3 ) ] · [ Au 6 S 2

The chemistry of polynuclear gold(I) complexes has attracted increasing attention in the past few decades. With a closedshell electronic configuration of d, gold(I) ions adopt a linear two-coordinate coordination geometry and tend to form weak metal⋯metal interactions, which were termed “aurophilic interactions” by Schmidbaur. They are found in a huge number of polynuclear aggregates that possess a wide diversity of configurations and were successfully traced in several early theoretical investigations by extended Hückel quantum chemical calculations. Due to the high stability and the relatively good accessibility of synthetic routes, chalcogenide-based polynuclear gold(I) complexes, especially sulfideand selenidebridged gold(I) complexes, are among the most popular systems in the gold family. Many polynuclear gold(I) clusters of bridging phosphane ligands, with pyramidal [Au3(μ3-S)] + units, are linked via metal⋯metal interactions. Examples include clusters with the formulae [Au5(PPh2)3(dppma2)], 4 [Au10Se4(dppm)4] 2+ (dppm = bis(diphenyl-phosphino)methane), [Au18Se8(dppthph)6] 2+ (dppthph = 2,5-bis(di-phenylphosphino)-thiophene) and a series of decanuclear compounds recently published by Yam and co-workers, [Au10S4{(Ph2P)2NCnH2n+1}4] 2+ and [Au10E4{(Ph2P)2NC6H4X}4] 2+ (n = 8, 12, 14, 18; E = S, Se; X = H, Me, OMe, F, Cl, Br). In this work, we report on further extension of the investigations considering ligands that are based on maleic anhydride. In particular, we used a chlorogold(I) precursor containing the 2,3-bis(diphenylphosphino)maleic anhydride (dppma) ligand, [(AuCl)2(dppma)], to form polynuclear gold(I) μ3-sulfido clusters. The dppma ligand is known to assist the stabilization of mononuclear 19-electron complexes by electron delocalization into the low-lying π* orbital of the phosphane ligand, which led to the formation of a number of stable 19-electron complexes of Mn and Co, for example [(dppma)Co (CO)3] and [(dppma)Mn(CO)4], in which the odd electron appears to be ligand-centered. This redox-active phosphane ligand seems to be an interesting point also for gold sulfide chemistry, as has been shown in some preliminary studies. Both the ligand and the respective gold(I) precursor [(AuCl)2(dppma)] were prepared according to literature methods and treated under inert conditions. Reaction of the latter with S(SiMe3)2 in CH2Cl2 (with traces of water) yielded a mixture of different complexes, [Au5(PPh2)3(dppma2)2] 4 and [Au24(PPh2)4S6(dppma2)8], 4,12 reported recently, and the yet unknown compound [Au10S2(PPh2)2(dppma2)4(dppma3)]· [Au6S2(dppma2)2(dppma3)] (1, Fig. 1), in single crystalline form according to the following reaction scheme: