Cooperative effects of electron donors and acceptors for the stabilization of elusive metal cluster frameworks: Synthesis and solid-state structures of [Pt_(19)(CO)_(24)(μ_4-AuPPh_3) _3]- and [Pt_(19)(CO) _(24){μ_4-Au_2(PPh_3)_2} _2]

摘要

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-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.