Computational Assessment and Understanding of C6 Product Selectivity for Chromium Phosphinoamidine Catalyzed Ethylene Trimerization

13 December 2021, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


One approach to selectively generate 1-hexene is through ethylene trimerization using highly active Cr N-phosphinoamidine catalysts ((P,N)Cr). Depending on the ligand, (P,N)Cr catalysts can either generate nearly pure 1-hexene or form 1-hexene with significant mixtures of other C6 mass products, for example methylenecyclopentane. Here we report DFT transition state modeling examining 1-hexene catalysis pathways as well as pathways that lead to alternative C6 mass products. This provided qualitative and semi-quantitative modeling of the experimental 1-hexene purity values for several (P,N)Cr catalysts. Consistent with previous computational studies, the key 1-hexene purity-determining transition states were determined to be β-hydrogen transfer structures from the metallacycloheptane intermediate. The origin of selectivity for these (P,N)Cr catalysts can be attributed to steric effects in the transition-state structure with coordinated ethylene that leads to C6 impurities.


Density functional theory
Transition state

Supplementary materials

Supporting Information
Computational details, additional mechanisms, pressure and temperature corrections, and entropy-scaled energies.


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