Continuous wave and pulse EPR as a tool for the characterization of monocyclopentadienyl Ti(III) catalysts

Monocyclopentadienyl Ti(III) catalysts in which the cyclopentadienyl ring has a heteroatom-functionalized side chain are used in the polymerization of olefins and the co-polymerization of ethylene with propylene, 1-hexene, 1-octene and styrene. In this work, we show that a combined continuous wave and pulse EPR study of such complexes can reveal structural information where other analytical methods fail. Hyperfine sublevel correlation (HYSCORE) spectroscopy is found to be a powerful method to identify the type of nuclei surrounding the Ti3+ ion. For the first time, the hyperfine and nuclear quadrupole data of Ti(III)-bound 14N nuclei are reported. The observed values are compared to known data of different transition metal complexes. Furthermore, the observed proton and lithium interactions are discussed.