Degree Type

Thesis

Date of Award

2020

Degree Name

Doctor of Philosophy

Department

Chemistry

Major

Organic Chemistry

First Advisor

Aaron D Sadow

Abstract

Organolanthanides are potential catalysts for variety of catalytic transformations such as heterofunctionalization of carbon-carbon multiple bonds and polymerization of alkenes. Ln3+ complexes are generally characterized as redox inactive, highly electropositive, and possess oxophilic character. Our group has developed rare earth alkyls and amides that are catalytically active in hydroamination, polymerization and dehydrocoupling reactions. This thesis describes the application of organolanthanum alkyl and kinetic measurements to understand the mechanistic pathway in the catalytic process. Also, we have studied the synthesis, catalysis, and kinetic measurements of C2 symmetric bisoxazoline zinc alkyl in dehydrocoupling reactions of slianes and alcohols.

The catalytic activity of homoleptic lanthanum trisalkyl La{C(SiHMe2)3}3 (LaR3) is studied in hydroboration of ketones, aldehydes, esters, and epoxides. These reactions are mostly conducted at room temperature and achieve products in high yield. Reactivity order of the substrates are as follows: aldehyde>ketone>ester>epoxide. Kinetic investigations on hydroboration of ester and epoxide indicate that the reaction is ternary, first order on both ester/epoxide and HBpin.

Converting homogeneous catalyst to heterogeneous catalyst may affect the catalytic performance in terms of its activity as bonding of the oxygen of silanol group with the metal makes metal more Lewis acidic. Also, ease of separation, recovery, and reusability of the catalyst are potential advantages of surface organometallic chemistry (SOMC). We grafted LaR3 onto SBA-15-type mesoporous silica nanoparticles (MSN) by reaction of excess amount of LaR3 and MSN at room temperature for 12 h. MSN was dehydroxylated at 550 °C (MSN550) and 700 °C (MSN700) prior to its reaction with LaR3. To better understand the grafting process and catalytic mechanisms, various analytical techniques were applied to characterize these materials, including elemental analysis, diffuse reflectance infrared spectroscopy (DRIFT), solution-state and solid-state nuclear magnetic resonance (SSNMR) spectroscopy. The catalytic activity of LnRn@MSN (Ln = Y, La) was investigated in two individual projects hydroboration and hydroamination. Both catalytic reactions were under ambient temperature. We also investigated the recycling and leaching tests on hydroboration and hydroamination reactions.

A series of zinc alkyl complexes PhBOXR1R2ZnR' (R' = Me, Et) supported by monoanionic bisoxazoline ligand Ph,HBOXMe2 (1,1-bis-(4-dimethyl-2-oxazolinyl)phenylmethane), Ph,HBOXPh,H (1,1-bis-(4-phenyl-2-oxazolinyl)phenylmethane) and Ph,HBOXiPr,H (1,1-bis-(4-isopropyl-2-oxazolinyl)phenylmethane) were synthesized. Chiral and achiral BOX were synthesized using dimethyl phenyl malonate and respective amino alcohols as a starting material. The synthetic steps consist of condensation, protection followed by cyclisation reactions result in the formation of bisoxazoline (BOXH). Monanionic bisoxazoline zinc alkyl complexes were synthesized by reaction of BOXH and ZnR'2 (R' = Et, Me) at room temperature. Zincalkyl complexes react with alcohols in less than 10 minutes to produce corresponding zincalkoxides. PhBOXMe2ZnMe is active in catalytic dehydrocoupling of silanes and alcohols reaction. Kinetic studies provide detailed information of the elementary reaction steps that shows the overall rate law varies from primary to secondary to ternary based on the concentration of silane and alcohol.

DOI

https://doi.org/10.31274/etd-20200624-7

Copyright Owner

Smita Patnaik

Language

en

File Format

application/pdf

File Size

174 pages

Available for download on Wednesday, June 16, 2021

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