The chemistry and catalytic activity of dehydrogenative silylation and hydroboration of complexes bearing semirigid ligands with group 14 elements

Author

Niroshani S. Abeynayake, Mississippi State UniversityFollow

ORCID

https://orcid.org/0000-0002-0081-5133

Issuing Body

Mississippi State University

Advisor

Montiel-Palma, Virginia

Committee Member

Hollis, Keith T.

Committee Member

Cui, Xin

Committee Member

Mlsna, Todd E.

Committee Member

Wipf, David O.

Date of Degree

12-9-2022

Document Type

Dissertation - Open Access

Major

Chemistry

Degree Name

Doctor of Philosophy (Ph.D)

College

College of Arts and Sciences

Department

Department of Chemistry

Abstract

Incorporation of silicon in the ligand backbone would yield electron-rich metal complexes upon coordination to transition metal complexes. The coordination chemistry of semirigid benzyl phosphines bearing a single or multiple phosphorus atoms and varying number of Si−H moieties has gained interest in recent years. This dissertation focuses on synthesizing silyl and germyl transition metal complexes of groups 9 and 10. Chapter II presents the synthesis of a family of four coordinated 14-electron rhodium complexes. The newly synthesized complexes were characterized in solution by multinuclear NMR spectroscopy and in the solid-state by single-crystal X-ray diffraction. These d⁶ complexes possess sawhorse geometry around the rhodium metal center. The catalytic activity of the synthesized Rh complexes and the analogous Ir complex towards hydrosilylation/ dehydrogenative silylation of alkenes is presented in this study. Importantly, it was observed that the selectivity of the catalytic reaction can modify the choice of the metal center, rendering hydrosilylation products upon the use of Rh or dehydrogenative silylated product upon the use of Ir. In chapter III, the results of our investigations on the catalytic activity in dehydrogenative silylation of alkenes by Rh₂(OAc)₄/ PPh₃ system are presented. Sacrificial hydrogen acceptor, norbornene, and PPh₃ play a key role in specificity favoring the dehydrogenative silylated product. The substrate scope and the possible mechanistic pathways are reviewed. Chapters IV and V present the synthesis of EP₃-type (E = Si, Ge) tetradentate ligands. We describe the synthesis via E−H bond activation and characterization of their nickel and cobalt complexes by spectroscopic means. Additionally, the solid-state structures of the complexes were confirmed by X-ray crystallography. The catalytic activity of the synthesized nickel hydrides was investigated in the hydroboration of aldehydes by pinacolborane (HBpin). The catalytic activity of the synthesized cobalt(I) complex was studied in the presence of (EtO)₃SiH with aldehydes and ketones bearing various functional groups under mild conditions. In Chapter VI, the syntheses of octahedral rhodium and iridium [(Ph₂P-o-CH₂-C₆H₄)₃E]MClH (M = Rh, Ir: E = Si, Ge) complexes bearing EP₃-type tetradentate ligands via EH bond activation are presented. We also describe the synthesis and characterization of platinum complexes supported by EP₃-type tetradentate ligands.

Recommended Citation

Abeynayake, Niroshani S., "The chemistry and catalytic activity of dehydrogenative silylation and hydroboration of complexes bearing semirigid ligands with group 14 elements" (2022). Theses and Dissertations. 5658.
https://scholarsjunction.msstate.edu/td/5658