Iridium alkane dehydrogenation catalysis from within a polymer scaffold

Our group is especially interested in structured polymers as scaffolds for catalysis as the environment created by the polymer scaffold has the potential to alter catalyst reactivity and selectivity. We have optimized an “arm-first” star polymer synthesis method with reversible addition-fragmentation chain transfer (RAFT) polymerization of styrenic monomers that allows us to selectively install our ligand precursors into the star polymer core. Metallation of these embedded ligands can result in polymer bound catalysts within these structures. RAFT polymerizations were chosen for their combination of functional group tolerance, control over dispersity, and ease of re-initiation. Copolymerization of a modified bisphosphinite pincer ligand precursor (vinyl-POCOPH) with styrene produces a linear polymer that can be metalated with iridium. Similarly, a linear homopolymer of styrene can be re-initiated in the presence of vinyl-POCOPH, styrene, and divinylbenzene to produce styrenic star polymers with the ligand precursor localized to the star core. Catalytic alkane dehydrogenation studies comparing the unmodified small molecule iridium complex with the linear and star polymer-bound complexes are ongoing.