Degree Type

Dissertation

Date of Award

1987

Degree Name

Doctor of Philosophy

Department

Chemistry

Abstract

Over thirty new zirconium chloride cluster compounds based on discrete Zr[subscript]6Cl[subscript]12 clusters centered by Be, B, C, N and H have been prepared in high yield and structurally characterized. The compounds fall into the family M[subscript] x(Zr[subscript]6Cl[subscript]12Z) Cl[subscript] n, where n ranges from zero to six, and span eleven structure types and two new stoichiometries for M[subscript]6X[subscript]12-type clusters, namely M[subscript]6X[subscript]13 and M[subscript]6X[subscript]16. Six new structure types, KZr[subscript]6Cl[subscript]13Be, K[subscript]2Zr[subscript]6Cl[subscript]15B, K[subscript]3Zr[subscript]6Cl[subscript]15Be, Cs[subscript]3Zr[subscript]6Cl[subscript]16C, Na[subscript]4Zr[subscript]6Cl[subscript]16Be and Rb[subscript]5Zr[subscript]6Cl[subscript]18B, and several variations on known structure types are involved.;The previously known zirconium chloride clusters, Zr[subscript]6Cl[subscript]12, M[superscript] I[subscript]2Zr[subscript]7Cl[subscript]18 and Zr[subscript]6Cl[subscript]15 have been shown to be stabilized by hydrogen, hydrogen and nitrogen atoms in the cluster center, respectively. NMR studies of Zr[subscript]6Cl[subscript]12H show the hydrogen atom is undergoing rapid isotropic movement within the cluster and is also coupled to an unpaired electron in the cluster to give a temperature-dependent chemical shift. KZr[subscript]6Cl[subscript]13Be contains beryllium-centered Zr[subscript]6 clusters and exhibits an unusual connectivity with shared edge-bridging chlorine atoms (Cl[superscript] i-i) and triply shared terminal chlorine atoms. Nine new examples of compounds in the Nb[subscript]6Cl[subscript]14 structure are included. M[subscript] xZr[subscript]6Cl[subscript]15Z compounds in four structure types, Ta[subscript]6Cl[subscript]15, CsNb[subscript]6Cl[subscript]15, K[subscript]2Zr[subscript]6Cl[subscript]15B, and K[subscript]3Zr[subscript]6Cl[subscript]15Be and several variations thereon are described. The differences between these structure types (which include the local geometry of the intercluster bridging chlorine atoms, the three-dimensional connectivity, the member of cations and the space group) and the relationship of the structures to one another are explored to show that the Nb[subscript]6F[subscript]15, Ta[subscript]6Cl[subscript]15, CsNb[subscript]6Cl[subscript]15, K[subscript]2Zr[subscript]6Cl[subscript]15B structures have distinct structural frameworks. Compounds in three new structure types with unshared terminal chlorine atoms, Na[subscript]4 Zr[subscript] 6 Cl[subscript]16Be, Cs[subscript]3 Zr[subscript]6Cl[subscript]16C and Rb[subscript]5 Zr[subscript]6 Cl[subscript]18B are also given.;Extended-Huckel calculations on empty and centered M[subscript]6X[subscript]18 clusters demonstrate the s and p valence orbitals of the interstitial atom interact strongly with symmetry equivalent Zr-Zr bonding cluster orbitals to form four lower lying metal-interstitial bonding orbitals. The 'matrix effect' and the strength of the zirconium to interstitial bonding are implicated in the differences in electron count observed between centered zirconium chloride clusters and the related centered zirconium iodide and empty niobium and tantalum halide clusters. ftn * This research was supported by the National Science Foundation - Solid State Chemistry - Grant DMR 8318616.

DOI

https://doi.org/10.31274/rtd-180813-12556

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Robin P. Ziebarth

Language

en

Proquest ID

AAI8721944

File Format

application/pdf

File Size

323 pages

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