Cluster growth and fragmentation in the highly fluxional platinum derivatives of Sn94- : Synthesis, characterization, and solution dynamics of Pt2@Sn174- and Pt@Sn9H3-

Sn 9 4- reacts with Pt(PPh 3 ) 4 in ethylenediamine/toluene solvent mixtures in the presence of 2,2,2-cryptand to give four different complexes: "Rudolph's complex" of proposed formula [Sn 9 Pt(PPh 3 ) x ] 4- (2), the previously reported [Pt@Sn 9 Pt(PPh 3 )] 2- ion (3), and the title complexes Pt 2 @Sn 17 4- (4) and Pt@Sn 9 H 3- (5). The use of Pt(norbornene) 3 instead of Pt(PPh 3 ) 4 gives complex 4 exclusively. The structure of 4 contains two Pt atoms centered in a capsule-shaped Sn 17 cage. The complex is highly dynamic in solution showing single, mutually coupled 119 Sn and 195 Pt NMR resonances indicative of an intramolecular liquidlike dynamic exchange process. Complex 5 has been characterized by selectively decoupled 1 H, 119 Sn, and 195 Pt NMR experiments and shows similar liquidlike fluxionality. In addition, the H atom scrambles across the cage showing small couplings to both Sn and Pt atoms. Neither 3 nor 4 obeys Wades rules; they adopt structures more akin to the subunits in alloys such as PtSn 4 . The structural and chemical relevance to supported PtSn 4 heterogeneous catalysts is discussed.