On the Role of Disproportionation Energy in Kumada Catalyst-Transfer Polycondensation

Jenna A Bilbrey; S Kyle Sontag; N Eric Huddleston; Wesley D Allen; Jason Locklin

doi:10.1021/mz3002929

On the Role of Disproportionation Energy in Kumada Catalyst-Transfer Polycondensation

ACS Macro Lett. 2012 Aug 21;1(8):995-1000. doi: 10.1021/mz3002929. Epub 2012 Jul 20.

Authors

Jenna A Bilbrey¹, S Kyle Sontag², N Eric Huddleston³, Wesley D Allen³, Jason Locklin³

Affiliations

¹ Department of Chemistry , ‡College of Engineering, Center for Nanoscale Science and Engineering, and §Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602, United States.
² Department of Chemistry , College of Engineering, Center for Nanoscale Science and Engineering, and §Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602, United States.
³ Department of Chemistry , College of Engineering, Center for Nanoscale Science and Engineering, and Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602, United States.

PMID: 35607024
DOI: 10.1021/mz3002929

Abstract

Kumada catalyst-transfer polycondensation (KCTP) is an effective method for the controlled polymerization of conjugated polymers. Nevertheless, side reactions leading to early termination and unwanted chain coupling cause deviations from the target molecular weight, along with increasing polydispersity and end group variation. The departure from the KCTP cycle stems from a disproportionation reaction that leads to experimentally observed side products. The disproportionation energies for a series of nickel-based initiators containing bidentate phosphino attendant ligands were computed using density functional theory at the B3LYP/DZP level. The initiator was found to be less favorable toward disproportionation by 0.5 kcal mol^-1 when ligated by 1,3-bis(diphenylphosphino)propane (dppp) rather than 1,2-bis(diphenylphosphino)ethane (dppe). Trends in disproportionation energy (E_disp) with a variety of bidentate phosphine ligands match experimental observations of decreased polymerization control. Theoretical E_disp values can thus be used to predict the likelihood of disproportionation in cross-coupling reactions and, therefore, aid in catalyst design.