Title

Evaluating the Structure Determining Factors of Alkali and Alkaline Earth Metal Amides

Date of Award

2010

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Advisor(s)

Karin Ruhlandt-Senge

Keywords

Alkaline earth metals, Amides, Co-ligand coordination

Subject Categories

Chemistry

Abstract

The chemistry of the alkali and alkaline earth metal amides has progressed exponentially in the last 50 years due to advances in synthetic methodologies and understanding of structure/function relationships. Despite these advances, the exploration of the heavy s-block metals has been marred by numerous challenges related to their high oxo- and hydrophillicity, tendency towards aggregation, and electrostatic metal-ligand interactions. The work presented herein addresses the effects that ligand size, neutral co-ligand coordination, and presence of secondary non-covalent interactions have on the chemistry of alkali and alkaline earth metal amides.

Use of sterically encumbering ligands in conjunction with neutral co-ligand coordination and their effects on the coordination chemistry of these metals is presented through a series of novel heavy alkali metal bis(bis(diphenylmethyl)silyl amides. These compounds exhibit a large number of non-covalent interactions in the form of metal-π contacts, allowing for the isolation of 1-D coordination polymers and a rare alkali metal separated amido species.

In addition, a novel family of heavy alkaline earth primary amides is presented. These compounds, of the type Ca/Sr/Ba[N(H)(Dipp)] 2 (hmpa) 3 (Dipp = 2,6-di-isopropylaniline; HMPA = hexamethylphosphoramide) are the first examples of homoleptic and monomeric primary amido species reported. They showcase the importance of non-covalent agostic interactions in coordinative metal saturation in both solution and solid-state.

The presence of stabilizing factors along with their importance and overall effect on ion-association, coordination numbers, and resulting structure/function relationships will be further discussed for both families of metals. Studying the factors influencing ion-association becomes requisite to understanding the chemistry of organometallic alkali and alkaline earth compounds, and recent findings in these topics will be discussed. These considerations highlight the delicate balance in the organometallic chemistry of early main group chemistry.

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