Oxidation state(s) of the active titanium species during polymerization of styrene to syndiotactic polystyrene catalyzed by Cp*TiMe3/B(C6F5)3, Cp*TiMe3/[Ph3C][B(C6F5)4], and Cp*TiCl2,3/MAO

A combined NMR/EPR investigation of the catalyst systems Cp * TiMe 3 /B(C 6 F 5 ) 3 , Cp * TiMe 3 / [Ph 3 C][B(C 6 F 5 ) 4 ], and Cp * TiCl 2,3 /MAO for the polymerization of styrene to syndiotactic polystyrene suggests that evidence for the involvement of EPR-active titanium(III) species as catalysts is ambiguous.