Cooperative effects of electron donors and acceptors for the stabilization of elusive metal cluster frameworks: synthesis and solid-state structures of [Pt19(CO)24(μ4-AuPPh3)3]- and [Pt19(CO)24{μ4-Au2(PPh3)2}2].

The anionic cluster [Pt(19)(CO)(22)](4-) (1), of pentagonal symmetry, reacts with CO and AuPPh(3)(+) fragments. Upon increasing the Au:Pt(19) molar ratio, different species are sequentially formed, but only the last two members of the series could be characterized by X-ray diffraction, namely, [Pt(19)(CO)(24)(μ(4)-AuPPh(3))(3)](-) (2) and [Pt(19)(CO)(24){μ(4)-Au(2)(PPh(3))(2)}(2)] (3). The metallic framework of the starting cluster is completely modified after the addition of CO and AuL(+), and both products display the same platinum core of trigonal symmetry, with closely packed metal atoms. The three AuL(+) units cap three different square faces in 2, whereas four AuL(+) fragments are grouped in two independent bimetallic units in the neutral cluster 3. Electrochemical and spectroelectrochemical studies on 2 showed that its redox ability is comparable with that of the homometallic 1.