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)24μ4-Au2(PPh3)22]

The anionic cluster [Pt19(CO)22]4-(1), of pentagonal symmetry, reacts with CO and AuPPh3+fragments. Upon increasing the Au:Pt19molar ratio, different species are sequentially formed, but only the last two members of the series could be characterized by X-ray diffraction, namely, [Pt19(CO)24(μ4-AuPPh3)3]-(2) and [Pt19(CO)24μ4-Au2(PPh3)22] (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. © 2013 American Chemical Society.