We discovered a highly active catalyst that is capable of polymerizing alkynes to give cyclic polyenes. Cyclic polymers exhibit remarkably different physical properties compared to their linear counterparts. Despite their interesting properties, laborious synthesis required for cyclic polymers have hindered development of this research field. Methods for the synthesis of cyclic polymers usually involve intramolecular coupling between the chain ends of linear precursors; however, the inherent limitation of this method is the requirement of dilute conditions and long reaction times. Recent discoveries in catalytic production of cyclic polymers offer exciting new avenues for their efficient production. Along with our polymer investigations we continue to develop more efficient , selective, and potentially living catalysts for cyclic polymer synthesis.

Manipulating the electronic and geometric structure of transition metal complexes through judicious ligand design is central to the evolution of modern organometallic chemistry. Presented with a vast choice of ligand architectures, it is now simply a challenge of matching the correct ligand with a particular metal ion in the appropriate oxidation state to achieve the desired outcome. In particular, it is now possible to manipulate the nucleophilicity of metal-carbon multiple bonds by employing the inorganic enamine effect. Resonance structures reveal the relationship between enamines and an inorganic version. Applying this concept, alkylidyne complexes rapidly deoxygenate carbonyl complexes, including carbon dioxide.

Enyne metathesis involves the reaction between an alkylidene and an alkyne. Numerous ruthenium carbenes and early metal alkylidenes react with alkynes. However, alkylidynes do not react with alkenes in “ynene” metathesis. Trianionic pincer ligands can induce unusually nucleophilic metal-carbon triple bonds. Thus, we hypothesized that if a trianionic pincer alkylidyne could be coaxed to undergo cycloaddition with a cyclic olefin it would inherently lead to a tethered alkylidene, and therefore poised to initiate ring expansion metathesis polymerization (REMP) to give cyclic polymers. The OCO trianionic W-complex depicted initiates the stereoselective REMP of norbornene to give cis and >99.5 syndiotactic cyclic polynorbornene.

This project takes advantage of a recent discovery in the Veige research group involving the 1,3-dipolar cycloaddition of metal-azides and metal-acetylides to give dinuclear-1,2,3-triazolates. The first inorganic click (iClick) reaction was successfully accomplished in the Veige laboratories in 2010. iClick covalently links metal ions through a triazolate bridge in the 1,5 positions to give homo-/heterobimetallic units that can form oligomers/polymers. Additionally, iClick has been extended to include several transition metals: Au, Pt, Ir, and Rh. Conjugated polymers incorporating metal ions in the main chain are important for their ability to delocalize excitons to create charge separation in the polymer. Conjugated polymers see use in OLEDs, chemical/physical sensing, and photovoltaics. In this project we have synthesized gold oligomers using iClick and aurophilic cluster formation. The formation of the cluster is reversible so we have the ability to tune the metallopolymer to give different properties such as absorption/emission and sensing.