Phosphanido-bridged triangular platinum clusters as versatile platforms: A personal account

• The flexibility of phosphanido bridges allows reversible cluster core isomerism.
• Pt cluster as platform for proton- or oxidation-induced P–C reductive elimination.
• Electrophilic metal reagents add to Pt3 clusters to give heterometallic clusters.
• Clusters with Pt–Cu, Pt–Ag, Pt–Au and Pt–Pd metal cores have been characterized.

In this Account, we discuss diverse aspects of the structural and chemical properties associated with phosphanido-bridged triangular platinum clusters, in particular the 44 valence electron cluster [Pt3(μ-PPh2)3Ph(PPh3)2] (1). Various structural isomers of this cluster have been obtained as a function of the crystallization solvents and X-ray diffraction analyses established that their Pt–Pt separations span a large range of distances, one of them witnessing a record change of 0.56 Å, from 3.074(1) to 3.630(1) Å, when going from one structural isomer to another. These “closed” and “open” triangular forms of 1 can be readily and reversibly interconverted, simply by changing the crystallization solvents. Their reactions with electrophilic reagents, such as protons and isolobal d10 metal fragments, which led to heterometallic, tetranuclear clusters, as well as with oxidants and silanes are discussed. It was found that the reductive coupling between the phenyl ligand and a phosphanido bridge in 1, which restores a PPh3 ligand in the coordination sphere of the cluster and thus represents the reverse of the transformation of a PPh3 ligand in PPh2 and Ph that occurs upon thermal activation of a Pt(0) precursor containing PPh3 ligands, is promoted by iodine oxidation or by protonation. We also present the structure of the new 44 valence electron mixed-metal palladium–platinum triangular cluster [PdPt2I2(μ2-I)(μ-PPh2)(PPh3)3] (3), which was obtained by oxidative-addition of a PdII–I bond of [PdI2(PPh3)2] at the Pt0 center of [Pt(C2H4)(PPh3)2].

Diverse aspects of the properties of phosphanido-bridged triangular platinum clusters, in particular the 44 valence electron cluster [Pt3(μ-PPh2)3Ph(PPh3)2] are discussed. They include the flexibility and reactivity of phosphanido bridges, cluster core isomerism, proton- and oxidation-induced P–C reductive elimination and the formation of heterometallic Pt–Cu, Pt–Ag, Pt–Au and Pt–Pd clusters.Figure optionsDownload as PowerPoint slide