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Date of Award

3-1976

Degree Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Supervisor

M.J. McGlinchey

Abstract

A series of substituted bis(fluorobenzene)chromium complexes, (C₆H₄FX)₂Cr, where X is ortho, meta and para H, F, Cl, CH₃ and CF₃, have been synthesized by cocondensing chromium atoms and fluoroarenes. The ¹⁹F n.m.r. chemical shifts of these compounds correlate well with those of the corresponding C₆F₅X system suggesting that the overall electron-withdrawing effect of a π-bonded chromium atom is similar to the effect of four ring fluorine substituents.

This correlation suggested that nucleophilic substitution reactions might be possible for fluorosubstituted bis(arene)chromium complexes; indeed bis(anisole) chromium was obtained in low yield from the reaction of bis{η-fluorobenzene)- chromium and sodium methoxide. Furthermore, a series of alkyl-and aryl-lithium reagents reacted readily with (C₆H₆)Cr(C₆F₆) at low temperature to yield polysubstituted products. Proton abstraction from the π-complexed C₆H₆ ring was a competing process and led to telomeric sandwich complexes of which several were identified spectroscopically.

The behaviour of these complexes was consistent with the view that the π-{C₆H₆)Cr moiety donated electron density to the C₆F₆ ring and, to investigate this further, a series of complexes (C₆H₆)Cr(C₆F₅X) was prepared via the lithium reagent (C₆H₆)Cr(C₆F₅Li). These data supported the view of the π-complexed C₆F₅X system being more electron rich than the free C₆F₅X rings.

These new sandwich complexes pose severe nomenclatural problems, and the CHROMARENE nomenclature has been proposed in an attempt to overcome these difficulties.

Preliminary studies with other metals, viz., iron and germanium have provided direct routes to ferrocenophanes and organogermenes respectively.

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