The [Sn₉Pt₂(PPh₃)]^2- and [Sn₉Ni₂(CO)]^3- Complexes: Two Markedly Different Sn₉M₂L Transition Metal Zintl Ion Clusters and Their Dynamic Behavior

[Sn9Pt2(PPh3)]2- (2) was prepared from Pt(PPh3)4, K4Sn9, and 2,2,2-cryptand in en/toluene solvent mixtures. The [K(2,2,2-cryptand)]+ salt is very air and moisture sensitive and has been characterized by ESI-MS, variable-temperature 119Sn, 31P, and 195Pt NMR and single-crystal X-ray diffraction studies. The structure of 2 comprises an elongated tricapped Sn9 trigonal prism with a capping PtPPh3, an interstitial Pt atom, a hypercloso electron count (10 vertex, 20 electron) and C3v point symmetry. Hydrogenation trapping experiments and deuterium labeling studies showed that the formation of 2 involves a double C−H activation of solvent molecules (en or DMSO) with the elimination of H2 gas. The ESI-MS analysis of 2 showed the K[Sn9Pt2(PPh3)]1- parent ion, an oxidized [Sn9Pt2(PPh3)]1- ion, and the protonated binary cluster anion [HSn9Pt2]1-. 2 is highly fluxional in solution giving rise to a single time-averaged 119Sn NMR signal for all nine Sn atoms but the Pt atoms remain distinct. The exchange is intramolecular and is consistent with a rigid, linear Pt−Pt−PPh3 rod embedded in a liquidlike Sn9 matrix. [Sn9Ni2(CO)]3- (3) was prepared from Ni(CO)2(PPh3)2, K4Sn9, and 2,2,2-cryptand in en/toluene solvent mixtures. The [K(2,2,2-cryptand)]+ salt is very air and moisture sensitive, is paramagnetic, and has been characterized by ESI-MS, EPR, and single-crystal X-ray diffraction. Complex 3 is a 10-vertex 21-electron polyhedron, a slightly distorted closo-Sn9Ni cluster with an additional interstitial Ni atom and overall C4v point symmetry. The EPR spectrum showed a five-line pattern due to 4.8-G hyperfine interactions involving all nine tin atoms. The ESI-MS analysis showed weak signals for the potassium complex [K2Sn9Ni2(CO)]1- and the ligand-free binary ions [K2Sn9Ni2]1-, [KSn9Ni2]1-, and [HSn9Ni2]1-.