Investigation of the polymerization of ethylene on CO-reduced Phillips catalyst (1 wt% chromium) by infrared spectroscopy reveals the presence of new OH bands. In particular, an OH-band appears at 3,605 cm−1, consistent with the interaction of the SiOH group with an adjacent Lewis acidic chromium center, Si–(μ-OH)–Cr. Polymerization with d4-ethylene leads to the formation of the isotopically shifted band at 2,580 cm−1, consistent with heterolytic C–H activation of ethylene over a Cr–O bond to generate the first Cr–C bond in ethylene polymerization with Phillips catalyst, as recently observed on well-defined Cr(III) silicates.
Graphical Abstract