Distinguishing Chain Growth Mechanisms in Metal-catalyzed Olefin Oligomerization and Polymerization Systems: C2H4/C2D4 Co-oligomerization/Polymerization Experiments Using Chromium, Iron, and Cobalt Catalysts

Abstract

A series of co-oligomerization and copolymerization reactions of C2H4/C2D4 (1:1) mixtures have been carried out using various transition metal catalysts based on Cr, Co, and Fe in combination with MAO. The oligomeric α-olefin products have been analyzed by GC and GC/MS, and the experimental results have been compared with the theoretical mass spectra derived from mathematical models. Solid polymer samples have been analyzed by 13C{1H} and 13C DEPT-135 NMR spectroscopy. C2H4/C2D4 co-oligomerization can be used as a method to differentiate between a metallacyclic or a Cossee-type chain growth mechanism in oligomerization systems. In the case of a metallacyclic mechanism, no H/D scrambling is observed, whereas for a Cossee-type mechanism, similar rates of chain propagation and chain termination (β-H elimination) result in rapid H/D scrambling of the C2H4/C2D4 feed. This method is therefore limited to oligomerization systems and cannot be applied in polymerization systems, where the rate of chain propagation ...