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 [Pt19(CO)22]4- (1), of pentagonal symmetry, reacts with CO and AuPPh3+ fragments. Upon increasing the Au:Pt19 molar 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)24{μ4-Au2(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.