All ETDs from UAB

Advisory Committee Chair

Gary M Gray

Advisory Committee Members

Aaron Lucius L Lucius

Charles L Watkins

Tracy P Hamilton

Houston Byrd

Chris Lawson

Document Type

Dissertation

Date of Award

2011

Degree Name by School

Doctor of Philosophy (PhD) College of Arts and Sciences

Abstract

The research described in this manuscript includes a study of the effects of alkali metal salts on the activities and regioselectivities of rhodium metallacrown ether catalysts for the hydroformylation of styrene. It also includes a complementary study of the binding of alkali metal cations to the model metallacrown ethers for the rhodium catalysts that provides insight into the factors affecting the activity and regioselectivity of styrene hydroformylation. Chapter 1 of this dissertation evaluates cis-Mo(CO)4(2,2'-C12H8O2)PO(CH2CH2O)4(2,2'-C12H8O2) metallacrown ether binding of alkali metal salts by application of binding density analysis to determine accurate binding constants by 31P{1H} NMR titrations in an optimized mixture of dichloromethane-d2 and tetrahydrofuran. The observed binding affinity is then related to the concentration of tetrahydrofuran (log Kobs = - 3.58 log [THF] + log Ka) using a newly developed solvent back-titration. FT-IR titrations show that alkali metal binding reduces π-back bonding between the Mo metal and the CO ligands, increasing the stretching force constants (kcis and ktrans) for all CO ligands by approximately 10 %. Chapter 2 of this dissertation uses the model independent, binding density titration analysis, solvent back-titration developed in Chapter 1, and continuous variation Job experiments of Li+ and Na+ alkali borate salts to study cation binding to cis-Mo(CO)4(2,2'-C12H8O2)PO(CH2CH2O)n(2,2'-C12H8O2) (n = 3, 4, 5). X-ray crystal structures and the solution cis-trans and monomer-oligomer equilibria of cis-Mo(CO)4(2,2'-C12H8O2)PO(CH2CH2O)n(2,2'-C12H8O2) and cis-PdCl2(2,2'-C12H8O2)PO(CH2CH2O)n(2,2'-C12H8O2) (n = 3, 5) have been analyzed and demonstrate that all of the metallacrown ethers exist as cis, monomers in solution and solid state only. Chapter 3 contains an extensive study of the hydroformylation of styrene catalyzed by a metallacrown ether complex formed by the in-situ reaction of Rh(acac)(CO)2 and (2,2'-C12H8O2)PO(CH2CH2O)4(2,2'-C12H8O2). The effects of addition of alkali metal salts, LiBPh4*3dme and NaBPh4, reaction solvent, and syngas pressure have been determined. These studies indicate that the regioselectivity of the catalysts is sensitive to the syngas pressure, the solvent and the presence of alkali metal salts.

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