Our Research

Overview

Our current research is focused on the applications of primary amido-functionalized N-heterocyclic carbene (NHC) and imidazole ligands. The incorporation of a basic primary amido group may allow the ligand to act as a proton shuttle during catalytic reactions (see scheme below), leading to reaction mechanisms that involve metal-ligand cooperation.

One possible application of these types of ligands is in base-free transfer hydrogenation. Transfer hydrogenation is an important methodology for reducing unsaturated substrates using a dihydrogen surrogate in place of hydrogen gas or traditional main group hydride salts. This reaction is commonly used in synthetic organic chemistry labs with industrial applications in pharmaceuticals and fine chemicals. Since a base is already incorporated in the ligand, reactions may not require added base. This makes reactions easier to perform and could allow for the reduction of base-sensitive substrates. Additionally, we are interested in developing catalysts that can operate in air. 

Ruthenium and Nickel Complexes of Primary Amido-Functionalized NHC Ligands

We discovered a series of nickel catalysts that can operate without base and in air. While catalytic activities are modest (50-60% yield in 20 h), this discovery presents a promising direction for future catalyst development.

We have extended this ligand design to ruthenium systems. We are also working on using this catalyst design for other chemical transformations, such as hydrogen-deuterium exchange. 

Ruthenium Complexes of Imidazole-2-Carboxamides

A second ligand design being explored in our lab is based on imidazole-2-carboxamide. These ligands still feature the primary amide functionality but involve imidazole coordination rather than the use of an NHC ligand. We are investigating the coordination chemistry of these ligands with ruthenium. The resulting ruthenium complexes are competent catalysts for the base-free hydrogenation of ketones and aldehydes under aerobic conditions. The x-ray crystal structure of one of these complexes is shown below.  

The emphasis of our current work is exploring the impact of modifying the imidazole carboxamido ligand on catalytic activity in both base-free transfer hydrogenation and acceptorless dehydrogenation reactions. 

Funding

Our research is currently funded by the National Science Foundation (CHE-2246470).