Chemistry and Chemical Biology ETDs

Publication Date

12-6-1974

Abstract

Binuclear complexes of the vanadyl(IV) tartrates have already been shown to exist both in the solid state and in solution. These complexes consist of two vanadyl(IV) ions bridged by two tartrato(4-) ligands, either of the same-~DD (or LL)-- or opposite--DL—enantiomeric configuration. (The meso isomer of tartaric acid will not form binuclear complexes with vanadyl(IV).) The DL complex is more stable than the DD complex due to a greater degree of staggering between the vicinal hydrogen atoms on each tartrate chain.

Investigations of vanadyl(IV) complexes with substituted tartaric acid ligands--specifically, (±)-dimethyltartaric acid and (±)-threomethyltartaric acid--have been undertaken to determine whether this same predicted stability ordering would still prevail and if in fact the substituted binuclear complexes were stable enough to form, given the greater steric strain involved in replacing the vicinal hydrogen atoms with methyl groups. A discussion of the number of isomers and symmetries of these complexes is presented, as well as a complete description of the syntheses of the ligands and the sodium salts of the coordination complexes.

The complexes have been characterized by pH titrations and optical and electron spin resonance spectra. Energy level orderings for both the DD and DL complexes have been proposed.

The results of these studies indicate that there is a considerable stereoselective effect- -a mar ked difference in the stability and optical properties of the DD complexes as opposed to the DL complexes. The predicted stability ordering DL>DD has been verified. The presence of binuclear structures has been confirmed by ESP studies for all complexes generated in solution and all but one of the complexes isolated as solids and redissolved (this exception was found to contain primarily species having no exchange coupling).

In addition, the absolute configurations of (±) -dimethyltartaric acid and (±)-threo-methyltartar-ic acid have been determined by a “KeyLock” complexation method using the vanadyl (IV) DD tartrate complex as a “Lock” to preferentially coordinate with the L configuration of a substituted tartaric acid to 1form a "DL" type complex. This method permits the rapid assignment of the absolute configuration of any alkyl- or aryl-substituted threo-tartaric acid having a water soluble salt; this technique also allows for 1the rapid determination of erythro/threo assignments.

Language

English

Document Type

Dissertation

Degree Name

Chemistry

Level of Degree

Doctoral

Department Name

Department of Chemistry and Chemical Biology

First Committee Member (Chair)

Robert Edwin Tapscott

Second Committee Member

William Fletcher Coleman

Third Committee Member

Guido Herman Daub

Fourth Committee Member

Edward A. Walters

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