Catalytic Synthesis of Butene-1 and Hexene-1 in the Homogeneous Oligomerization of Ethylene in the Presence of Nickel Complexes Based on N-Heteroaryl-Substituted α-Diphenylphosphinoglycines

Abstract

It has been shown in tests that N-heteroaryl-substituted α-diphenylphosphinoglycines, namely, N-(pyrazin-2-yl) α-diphenylphosphinoglycine, N-(pyridin-2-yl) α-diphenylphosphinoglycine, and N‑(pyrimidin-2-yl) α-diphenylphosphinoglycine, which are synthesized by the three-component condensation of diphenylphosphine, the respective primary amine, and glyoxylic acid monohydrate, being combined with Ni(COD)₂, where COD is cyclooctadiene-1,5, are capable of generating active forms of catalysts for the selective homogeneous dimerization and trimerization of ethylene to form butene-1 and hexene-1 as the main products. The studied organonichel catalyst systems provide a yield of short-chain (C₄–C₆) olefins at a level of 90% with a linear α-olefin selectivity of 97%. Studies of the effect of temperature on the homogeneous oligomerization of ethylene using the synthesized compounds have revealed that the process run at an optimum temperature of 80–105°C and an optimum ethylene pressure of 20–35 atm provides the highest butene-1 and hexene-1 selectivity. Under these conditions, the butene selectivity is recorded at a level of 71.4–72.6% (butene-1 selectivity of 69.3–71.1%), while the hexene selectivity is 20.6–21.2% (hexene-1 selectivity of 19.2–19.5%). The optimum duration of the oligomerization process at a temperature of 105°C is 1.5 h. The butene-1 and hexene-1 formation rate is 168.1 and 47.3 g_olig \({\text{g}}_{{{\text{Ni}}}}^{{ - 1}}\) h^–1, respectively.