Synthesis of Linear α‑Olefin Distributions with Flexible Mean Molecular Weight by a Ti-Al-Ni Catalyst System

The catalytic synthesis of linear α-olefins from ethylene is a key reaction in the chemical industry and one of the most important applications of homogeneous catalysis. Thus, novel protocols or concepts for the synthesis of linear α-olefins are highly desirable. Herein, we describe a trimetallic catalyst system (Ti-Al-Ni) consisting completely of earth-abundant metals. The titanium catalyst mediates coordinative chain transfer polymerization to the chain transfer agent triethylaluminum with multiple ethylene insertions prior to chain transfer. This Ti catalyst is combined with a simultaneously operating nickel catalyst. The nickel catalyst also undergoes chain transfer, displaces the grown alkyl chains via β-hydride elimination/transfer forming linear α-olefins, and recycles the chain transfer agent. The catalyst combination permits the highly efficient synthesis of various linear α-olefin distributions with flexible mean molecular weight with one catalyst system. Activities of more than 10000 kgeth mol–1 bar–1 h–1 have been observed for most of the runs, and a catalyst half-life of more than 2 h has been monitored. For example, we synthesized distributions with a mean molecular weight (M n) ranging from 260 to 7000 g mol–1. Such linear α-olefin distributions are difficult to synthesize, especially employing a single catalyst system. The reaction can be substoichiometric or formally catalytic regarding Al.