Title

Progress in molecular heterobimetallic alkaline earth metal chemistry: New synthetic strategies, structural features and properties

Date of Award

2007

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Keywords

Alkaline earth metals, Organomettalic complexes, Aryloxides, Secondary interactions, Heterobimetallic, Group 2

Subject Categories

Chemistry | Inorganic Chemistry | Physical Sciences and Mathematics

Abstract

Heterobimetallic compounds continue to be vital in synthetic and materials chemistry. In comparison their homometallic components, heterobimetallic compounds display unique chemical properties. Investigations on mixed metal compounds involving the alkaline earth metals are extensive for magnesium but the coordination chemistry and potential applications of corresponding heavy Group 2 (Ca, Sr, and Ba) metals have yet to be explored. Previous attempts to prepare such compounds only led to the isolation of homometallic species. The preparation of these species remains a challenge due to limited available synthetic strategies, and suitable ligand and solvent systems.

This work describes the synthesis and characterization of a family of molecular heterobimetallic alkaline earth metal complexes. The combinations of alkaline earth metals with alkali metals, rare earth metals and combination of metals within Group 2 are explored. A series of novel mixed metal lithium/magnesium complexes bearing different aryloxo ligands, in addition to a selection of donors have been prepared and analyzed to demonstrate their intricate role in the structural chemistry of the target compounds.

In addition, a new class of heterobimetallic compounds involving heavy Group 2 and Group 1 metals using 2,6-diphenylphenol (HOdpp) as the ligand is presented. These compounds, of the type [M n {Ae(Odpp) 2+n }] (M = Li, Na, K or Cs; Ae = Ca, Sr or Ba), are the first representatives of alkali/heavy alkaline earth metal species of low nuclearity. All compounds display extensive metal-p-interactions, believed to be a key factor in stabilizing these highly reactive species. Prepared as donor-free as well as heteroleptic complexes, these compounds provide critical insights into solvation versus intramolecular interactions.

Investigations on heterobimetallic compounds were also extended to mixed metal Ae/Ae' (Ae = Ba, Ae' = Sr or Mg) and Ae/Ln (Ae = Ba, Ln = Eu, Sm, Yb). The structural features displayed by these complexes further illuminate the similarities and differences in the chemistry of alkaline earth and rare earth metals.

The target compounds were prepared using a powerful synthetic methodology, solid state direct metalation. We present this approach as a highly promising entry into heavy alkaline earth metal derivatives.

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