Endohedral Plumbaspherenes of the Group 9 Metals: Synthesis, Structure and Properties of the [M@Pb<sub>12</sub>]<sup>3−</sup> (M=Co, Rh, Ir) Ions
Ai‐Min Li, Yi Wang, Domonique O. Downing, Fu Chen, Peter Y. Zavalij, Alvaro Muñoz‐Castro, Bryan W. Eichhorn
Abstract
Abstract The icosahedral [M@Pb 12 ] 3− (M=Co( 1 ), Rh( 2 ), Ir( 3 )) cluster ions were prepared from K 4 Pb 9 and Co(dppe)Cl 2 (dppe=1,2‐bis(diphenylphosphino)ethane)/[Rh(PPh 3 ) 3 Cl]/[Ir(cod)Cl] 2 (cod=1,5‐cyclooctadiene), respectively, in the presence of 18‐crown‐6/ 2,2,2‐cryptand in ethylenediamine/toluene solvent mixtures. The [K(2,2,2‐cryptand)] + salt of 1 and the [K(18‐crown‐6)] + salt of 3 were characterized via X‐ray crystallography; the ions 1 and 3 are isostructural and isoelectronic to the [Rh@Pb 12 ] 3− ( 2 ) ion as well as to the group 10 clusters [M′@Pb 12 ] 2− (M′=Ni, Pd, Pt). The ions are all 26‐electron clusters with near perfect icosahedral I h point symmetry. Clusters 1 – 3 show record downfield 207 Pb NMR chemical shifts due to σ‐aromaticity of the cluster framework. Calculated and observed 207 Pb NMR chemical shifts and 207 Pb– x M J ‐couplings ( x M= 59 Co, 103 Rh, 193 Ir) are in excellent agreement and DFT analysis shows that the variations of 207 Pb NMR chemical shifts for the [M@Pb 12 ] 2, 3− ions (M=Co, Rh, Ir, Ni, Pd, Pt) are mainly governed by the perpendicularly oriented σ 11 component of the chemical shift anisotropy tensor. The laser desorption ionization time‐of‐flight (LDI‐TOF) mass spectra contain the molecular ions as well as several new gas phase clusters derived from the parents. The DFT‐minimized structures of these ions are described.