Novel intercluster compound between a heptakis{triphenylphosphinegold(I)}dioxonium cation and an α-Keggin polyoxometalate anion

A novel intercluster compound, [{{Au(PPh3)}4(μ4-O)}{{Au(PPh3)}3(μ3-O)}][α-PW12O40]·EtOH (1) constructed between a heptakis{triphenylphosphinegold(I)}dioxonium cation and an α-Keggin polyoxometalate (POM) is synthesized and unequivocally characterized by elemental analysis, TG/DTA, FTIR, X-ray crystallography, solid-state CPMAS 31P NMR and solution (1H, 31P{1H}) NMR. The heptagold(I) cluster was formed during the course of carboxylate elimination of a monomeric phosphinegold(I) carboxylate precursor, i.e., [Au((RS)-pyrrld)(PPh3)] ((RS)-Hpyrrld = (RS)-2-pyrrolidone-5-carboxylic acid), in the presence of the sodium salt of an α-Keggin POM, Na3[α-PW12O40]·9H2O. Compound 1 was formed by ionic interaction between the heptagold(I) cluster cation and the α-Keggin POM anion. The heptagold(I) cluster unit was formed by four inter-cationic aurophilic interactions between the tetragold(I) cluster unit and trigold(I) cluster unit. The tetragold(I) cluster unit and trigold(I) cluster unit contained μ4-O and μ3-O atoms, respectively.