Transition Metal Catalyzed Depolymerization of Polyethylene Terephthalate and Synthesis of a Novel Redox-Active Ligand

Post-consumer plastic and polymer waste accumulation in recent years continues to become more of a problem. One of the common polymers that has become ubiquitous to modern life is polyethylene terephthalate, a polymer that makes up 6.2% of all polymers produced and only 39% of which is recycled in the US annually.1,5 In this study a new catalyst was for the methanolysis of PET and compared to a common organic base, 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), that has been used in academia and industry for the depolymerization of PET. In this study it was concluded that yttrium (III) acetylacetonate hydrate was a more active catalyst for the methanolysis of PET at 120 °C in comparison to TBD. It was also determined that there is no co-catalytic effect between yttrium (III) acetylacetonate hydrate and TBD when used in combination. The use of manganese (II) acetate tetrahydrate was also explored as a potential catalyst and was found to shown significant reactivity. However, it was concluded that the optimal conditions for PET methanolysis had not been reached and that further research into reaction times as well as co-solvents needs to be conducted. The synthesis of a novel o-phenylenediamine ligand functionalized with a labile phosphine substituent was also explored with the end goal of metalation and implementation in the methanolysis of PET. It has been assumed through nuclear magnetic resonance spectroscopy (NMR) characterization that the N,N’-(1,2-phenylenediamine)bis[3-(diphenylphosphanyl)-propanamide]-borane precursor was successfully synthesized and isolated. The subsequent deprotection of the N,N’-(1,2-phenylenediamine)bis[3-(diphenylphosphanyl)-propanamide]-borane complex was performed but has not been fully characterized. The 31P NMR does indicate a fully deprotected tertiary organophosphine. Through this work a detailed procedure for the ligand precursor has been laid out and developed so that the synthesis may now be scaled up, further characterized, metalated, and used to support catalysis.