Understanding tantalum-catalyzed ethylene trimerization: When things go wrong

Ethylene oligomerization to linear low-molecular-mass α-olefins is an open industrial challenge. Ta-based catalysts are promising systems, but the unclear understanding of their behavior prevents systematic advances in the field. We demonstrate here that a well-defined (î -SiO)₃Ta ^III species is able to promote ethylene oligo-/polymerization without any cocatalyst, confirming that the active species in Ta systems corresponds to a Ta^III species. DFT calculations on a series of Ta systems ranging from ethylene trimerization to ethylene polymerization catalysts highlight the key factors controlling their experimental behavior. Comparison of these Ta systems allows one to set general rules for the rational development of new ethylene Ta oligomerization catalysts.