Synthesis and Characterization of Transition Metal Pincer Complexes on a Silica Polyamine Composites for Catalytic Applications

Author

Abdul Goni

Year of Award

2016

Document Type

Dissertation

Degree Type

Doctor of Philosophy (PhD)

Degree Name

Chemistry (Inorganic Option)

Department or School/College

Department of Chemistry

Committee Chair

Edward Rosenberg

Commitee Members

J. B. Alexander Ross, Garon Smith, Orion Berryman, Nicholas Natale

Publisher

University of Montana

Abstract

There are two main parts of this dissertation: (i) Investigation of the most efficient method for loading and synthesizing catalytically active pincer metal complexes on a silica polyamine composite, BP-1, and (ii) study of the catalytic activity of the immobilized pincer complexes on the BP-1 surface.

Three methods were investigated to immobilize pincer complexes on BP-1 using PONOP pincer complexes of Ru, Rh, Ni and Pd. Method 1, appeared to be the most suitable and effective process to load the pincer complexes: the immobilization proceeded by a two-step Mannich reaction with the addition of preassembled pincer metal complexes to BP-1. The complexes on BP-1 were characterized by solid state NMR, FT-IR, elemental analysis, and metal digestion studies. The model solution experiments between pincer complexes and n-butylamine revealed electrophilic substitution in both the meta- and para-position of pyridine ring of the pincer complexes by Mannich intermediate.

The catalytic reactivity of immobilized (PNN)RuH(Cl)(CO) and (PONOP)RuH(Cl)(CO) on BP-1 was studied in the dehydrogenative coupling of alcohols to esters and H2 reactions. Moderate to good ester yields were realized with both immobilized systems without using any base and in the presence of KOH. The homogeneous reactions required a base for catalysis. The amine functionality on BP-1 functioned as a base to generate active pincer catalyst on the BP-1 surface. Both immobilized catalysts were recycled for multiple alcohol reaction cycles. BP-1-Ru-PNN showed alcohol conversions up to five cycles, whereas BP-1-Ru-PONOP was found to be survived up to the fourth catalytic cycle. Four control experiments were carried out using alcohol and both of the immobilized systems. The results revealed the heterogeneity of alcohol catalysis by both BP-1-Ru-PNN and BP-1-Ru-PONOP systems. The composite catalysts were also tested in amide formation reactions from amines and alcohols. Instead of generating amides, the imines formations were realized by the coupling of amines in both cases.

This study opened a new catalytic method for important metal pincer complexes in their known catalytic reactions where the requirement of using a base is eliminated for the catalysis by the utilization of a solid support with basic functionality. It also suggested different immobilization approaches which will save the relatively expensive pincer catalysts for multiple uses in catalysis.

Recommended Citation

Goni, Abdul, "Synthesis and Characterization of Transition Metal Pincer Complexes on a Silica Polyamine Composites for Catalytic Applications" (2016). Graduate Student Theses, Dissertations, & Professional Papers. 10861.
https://scholarworks.umt.edu/etd/10861