Aurophilic interactions in polynuclear Au(I) complexes with phosphine ligands containing imidazole rings

Aurophilic interactions in polynuclear Au(I) complexes with phosphine ligands containing imidazole rings Fiorella Bachechiaa*, Alfredo Burinib, Rossana Galassib aIstituto di Strutturistica Chimica, C.N.R., Area della Ricerca di Roma, C.P. 10, 00016 Monterotondo St. (Roma), Italy., bDipartimento di Scienze Chimiche, Università di Camerino, 62032 Camerino, Italy. E-mail: fiorella.bachechi@ic.cnr.it Keywords: gold complexes, aurophilicity, crystal structures The tertiary phosphines of the type (Bzim)3-nPhnP, where Bzim is 1-benzyl-2-imidazolylphosphine and n varies from 0 to 2, were synthesised as part of a program aimed to the study of the coordination chemistry of phosphines containing imidazole rings. The softer character of imidazole, with respect to other heterocycles, turned out to be useful in the stabilization of complexes with soft metals as those of Group 11 in low oxidation states. These ligands can behave as monodentate or as P, N bidentate forming dinuclear cationic complexes. With Au(I) they were found to be able to favour the formation of intraand intermolecular aurophilic interactions. TheAu(I) complexes assume considerable interest when aurophilic bonds occur between gold atoms, since their chemical and physical properties change to particular characteristics with potential applications in electronic, optical or sensor devices. In particular short Au•••Au interactions are considered related to optoelectronic properties as observed in a number of polynuclear gold compounds. Here the structures of two Au(I) complexes are reported. The binuclear complex [μ-(Bzim)Ph2PAu2(C6F5)2] adopts a folded conformation with parallel, eclipsed C6F5 rings and a corresponding short AucccAu contact of 3.033(2)Å. The tetranuclear cluster complex {[μ-N,N’-(Bzim)3PAuCl]2 Au2}2+c AuCl2 - c AuCl4 - consists in a 12-membered macrocycle with two gold atoms coordinated to two (Bzim)3P molecules, in bridging mode, through the nitrogen atoms of the imidazole rings and two gold atoms coordinated to the phosphorus atoms of the (Bzim)3P ligands. Two chloride atoms complete the Au bicoordination. Three strong aurophilic interactions, Au(1)cccAu(4) [2.989(2)Å], Au(2)cccAu(3) [3.014(2)Å] andAu(1)cccAu(2) [3.257(3)Å], occur.Aweak gold-gold contact, Au(3)cccAu(4) [3.766(2)Å], is also present. Understanding molecular interactions 23rd