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Modeling metal-catalyzed polyethylene depolymerization: [(Phen)Pd(X)]+(X = H and CH3) catalyze the decomposition of hexane into a mixture of alkenes via a complex reaction network

journal contribution
posted on 2023-05-20, 22:55 authored by Parker, K, Weragoda, GK, Allan CantyAllan Canty, Ryzhov, V, O'Hair, RAJ
The ternary Pd complexes [(phen)Pd(H)]+ (1-Pd) and [(phen)Pd(CH3)]+ (5-Pd) (where phen = 1,10-phenanthroline) both react with hexane in a linear ion trap mass spectrometer, forming the C–H activation product [(phen)Pd(C6H11)]+ (3-Pd) and releasing H2 and CH4, respectively. Density functional theory (DFT) calculations agree well with the experiments in predicting low barriers for these reactions proceeding via a metathesis mechanism. Species 3-Pd undergoes extensive fragmentation, or “cracking”, of the hydrocarbon chain when sufficient energy is supplied via collision-induced dissociation (CID), resulting in the extrusion of a mixture of alkenes, methane, and hydrogen. DFT calculations show that Pd “chain-walking” from α (terminal carbon) to β and from β to γ positions can proceed with barriers sufficiently below those required for chain “cracking”. The fragmentation reactions can be made catalytic if 1-Pd and 5-Pd produced by CID of 3-Pd are allowed to react with hexane again. Ni complexes largely mirrored the chemistry observed for Pd. Both 1-Ni and 5-Ni reacted with hexane, forming 3-Ni, which fragmented under CID conditions in a fashion similar to 3-Pd. In contrast, only 5-Pt reacted with hexane to form 3-Pt, which fragmented predominantly via sequential losses of H2.


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School of Natural Sciences


Amer Chemical Soc

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