Degree Type

Dissertation

Date of Award

1991

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Robert J. Angelici

Abstract

Basic organometallic complexes are important in many catalytic and stoichiometric reactions. Thus, to determine the factors controlling metal basicity, the heats of protonation ([delta]H[subscript] HM) of organometallic complexes have been studied by titration calorimetry. The protonation reactions are done with triflic acid (CF[subscript]3SO[subscript]3H) in 1,2-dichloroethane (DCE) solution at 25.0°C (eq 1). ML[subscript]x+CF[subscript]3SO[subscript]3H DCE[over] 25.0° C [HML[subscript]x] [superscript]+CF[subscript]3SO[subscript]3[superscript]-; [delta] H[subscript]HM\eqno(1);Increasing the number of methyl groups (N[subscript] Me) in the cyclopentadienyl ring of Cp[superscript]'Ir(1,5-COD) (Cp[superscript]' = C[subscript]5Me[subscript]x H[subscript]5-x, x = 0, 1, 3-5) complexes results in an increase in Ir basicity by -5.7 kcal mol[superscript]-1 on going from ( C[subscript]5 H[subscript]5)Ir(1,5-COD) (-22.8 kcal mol[superscript]-1) to ( C[subscript]5 Me[subscript]5)Ir(1,5-COD) (-28.5 kcal mol[superscript]-1). When [delta]H[subscript] HM of Cp[superscript]'Ir(1,5-COD) is plotted against N[subscript] Me, a linear correlation is obtained with each Me group worth 1.1 kcal mol[superscript]-1 towards an increase in the basicity of Cp[superscript]'Ir(1,5-COD). An analysis of the effect of C[subscript]5 H[subscript]5 vs C[subscript]5 Me[subscript]5 on the basicity of Ir in terms of [delta]H[subscript] HM, [delta]G°, and [delta]S° is also discussed;Changing the phosphine ligand in CpIr(CO)(PR[subscript]3) complexes results in a linear increase in the basicity ([delta]H[subscript] HM) of Ir from -29.2 kcal mol[superscript]-1 (PR[subscript]3 = P(p-ClC[subscript]6H[subscript]4)[subscript]3) to -33.2 kcal mol[superscript]-1 (PR[subscript]3 = PMe[subscript]3). There is a linear correlation between [delta]H[subscript] HM and free phosphine basicity ([delta]H[subscript] HP) with a slope of 0.298. Furthermore, the basicities of Fe(CO)[subscript]3(PR[subscript]3)[subscript]2 complexes also correlate linearly with [delta]H[subscript] HP but a larger slope (0.916) is obtained. The basicities of the Ir and Fe also show linear correlations with their respective [upsilon](CO) values;The [delta]H[subscript] HM values of Fe(CO)[subscript]3[Ph[subscript]2 P(CH[subscript]2)[subscript]nPPh[subscript]2] (n = 1-4) complexes become less exothermic from -24.0 kcal mol[superscript]-1 (n = 1) to -20.1 kcal mol[superscript]-1 (n = 4) by increasing the size of the chelate. In contrast, the free bidentate phosphine ligands become more basic, as measured by [delta]H[subscript] HP, with increasing chelate size. The Fe chelate complexes are also substantially more basic than the respective non-chelate derivatives. The trend in Fe basicities with chelate size and the comparison to the basicities of the non-chelated compounds are ascribed to distortions of the Fe(CO)[subscript]3(L[superscript]\capL) complexes by the chelate ligand.

DOI

https://doi.org/10.31274/rtd-180813-12841

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

John R. Sowa, Jr.

Language

en

Proquest ID

AAI9126251

File Format

application/pdf

File Size

209 pages

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