Our Research

Overview

Our current research is focused on the applications of carboxamido-functionalized imidazole ligands. The incorporation of a basic carboxamido 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 Complexes of Imidazole-2-Carboxamides

One of the main ligand designs being explored in our lab is based on imidazole-2-carboxamide. These ligands feature carboxamido functionality and involve  coordination through an imidazole ring. 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.  More information about this work can be found here.

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.  We have shown that increasing the steric profile of the carboxamido substituent (labeled "A" below), increases the catalytic activity of the complexes. The increased steric profile also leads to more rapid degradation of the complexes. More details on this work can be read here.

In addition to the ligand modifications described above, we are investigating ligands that contain additional functionality that we hope will either serve as proton shuttles or lead to more structurally diverse complexes to test for catalysis.

Nickel Complexes of Primary Amido-Functionalized NHC Ligands

In our early work, 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, and can be read about here.

Funding

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