Effect of an additional donor on decene formation in ethylene oligomerization catalyzed by a Cr/PCCP system: a combined experimental and DFT study†
A two-carbon bridged diphosphine (PCCP) ligand bearing an ortho-methoxy substituent in the phosphine phenyl group has been synthesised and applied in Cr-catalysed ethylene oligomerization. Compared to previous catalysts, the Cr catalytic system exhibited a higher selectivity toward the C10 fraction of up to 28.4 wt%, achieving a high reactivity of up to 1530 kg/(g Cr/h). The major product produced by the Cr/PCCP catalyst is 1-hexene with a selectivity of 64.1%. A detailed theoretical investigation by DFT calculations on the co-trimerization of ethylene and 1-hexene shows that the coordination of the oxygen atom of a methoxy moiety to the chromium center might be a key factor for the highly selective formation of 1-hexene. Moreover, the calculation results are consistent with the experimental observations on the distribution of decene isomers.