Synthesis and Characterization of Bimetallic Zintl Clusters and their Use in the Fabrication of Intermetallic Nanoparticles

Thumbnail Image


Publication or External Link






In this thesis, the synthesis, characterization and applications of bimetallic Zintl clusters are explored. Zintl ions are polyanions of main group elements, primarily of the heavier elements of groups 14 and 15. The closo-Sn9Ir(cod)3-, Sn9Rh(cod)3-, and Pb9Ir(cod)3- ions were prepared from precursors E94- (E = Sn, Pb), [M(cod)Cl]2 (M = Rh, Ir) and 2,2,2-crypt in ethylenediamine/toluene solvent mixtures. The clusters were isolated and characterized via NMR spectroscopy and single-crystal X-ray diffraction studies. The closo-E9Ir(cod)3- ions are the first known Ir(I) Zintl clusters and are examples of isostructural Sn/Pb homologues. All three complexes have 22-electron, bicapped square-antiprismatic structures and pseudo-C4v point symmetry with the Ir(cod) and Rh(cod) vertices attached in an η4 fashion. The Sn9Rh(cod)3- ion possesses 119Sn NMR chemical shifts that are consistent with other known Sn94- transition metal derivatives. The structural studies and 1H and 13C NMR studies showed significant charge transfer to the cod ligands.

Novel Rh@Sn123- and Rh@Pb123- ions have been prepared and isolated in the solid state and the latter has been studied via 207Pb NMR. The ions are 26-electron clusters with near perfect icohsahedral Ih point symmetry. Additionally, Ir@Pb123- and the previously isolated Ir@Sn123- ion [Fässler et al. 2010, Chem. Eur. J.] were detected for the first time via 207Pb and 117Sn NMR, respectively. The 207Pb NMR of Rh@Pb123- and Ir@Pb123- have the most downfield 207Pb signals known to date, due to their σ-aromaticity.

The Sn94- and As73- Zintl ions were shown to be effective reducing agents in the synthesis of three novel transition metal complexes. The synthesis and crystallographic characterization of the novel [Rh2H(PPh2)2(PPh3)3]-, Co3(CO)73-, and [(C3H7N2O)3Ir4(CO)9]3- ions are reported for the first time and cannot be prepared using traditional reducing agents.

Controlled I2 oxidations of preformed Zintl clusters Pt@Sn9Pt(PPh3)2- and Sn9Ir(cod)3-, give well ordered tin-rich intermetallic nanoparticles of PtSn4 and Ir3Sn7, respectively. The intermetallics were characterized by HR-TEM and XRD analysis. Both clusters have strong structural similarities with the final intermetallic, which appears to be an important factor in determining the phase of the resulting intermetallic nanoparticles. Despite the 1:9 (Ir:Sn) atomic ratio of the Sn9Ir(cod)3- cluster, ordered Ir3Sn7 nanoparticles were formed instead of the compositionally-similar IrSn4 phase. PtSn4 is difficult to prepare by traditional methods and isolate due to the formation of other known Pt-Sn phases, such as PtSn, PtSn2 and Pt3Sn.