Research

Our group’s current research sits at the cutting edge of organometallic synthesis, aiming to take compounds that were previously considered as ‘laboratory curiosities’ towards working as effective non-innocent ligands in catalytic transformations. For this, we have developed a range of low-valent group 13 and group 14 species which can act as Single-Centre Ambiphiles (Figure 1).

These species, when combined with a transition-metal element, act simultaneously as σ-donors and electron acceptors, due to their having a lone-pair of electrons and at least one vacant p-orbital. These ligands, then, can play an active role in substrate binding and activation. Importantly, due to the high Lewis acidity of the ligand, ‘Umpoled’ (or reversed) bond activation becomes possible, allowing for previously unobserved bond activation mechanisms which we will take forward into novel catalytic processes. The pro-ligands which will form the backbone of the Single-Centre Ambiphile ligands are the cornerstone of this work. These incorporate a chelating phosphine arm to increase the stability of the formed transition-metal catalysts, are are derived from classical (aryl)(silyl)amines. These can thus be readily modified in terms of both sterics and electronics, giving us an enormous capacity for the fine-tuning of these systems, leading to a greater understanding of this fascinating chemistry. An example of such a pro-ligand, and the resulting cationic GeII Single Centre Ambiphile ligand is shown below:

A central goal of ours is the ‘Umpoled’ activation of ammonia, to generate reactive transition-metal hydride species (Figure 1). In understanding the capacity for the described Single-Center Ambiphile systems to achieve this reaction, we aim to achieve the catalytic hydroamination of alkynes and alkenes with ammonia, in the synthesis of amines (Scheme 1). This process is considered a Holy Grail in modern chemical catalysis, in that current industrial amine synthesis is typically stoichiometric (i.e. uncatalyzed), generating up to ~300% waste (relative to product amines), whilst using highly toxic and corrosive feedstocks such hydrogen cyanide (vis. The Ritter process).