Kinetic Investigation of the Polymerization of 1-Hexene by the {[t-BuNON]ZrMe}[B(C 6 F 5 ) 4 ] Initiator

We have investigated the rates of polymerization of 1-hexene by cationic monoalkyl zirconium catalysts that contain the [t-BuNON] 2 - ligand ([t-BuNON] 2 - = {[(CH 3 )(CD 3 ) 2 CN-o-C 6 H 4 ] 2 O} 2 - ). Catalysts obtained by activation of [t-BuNON]ZrMe 2 with [Ph 3 C][B(C 6 F 5 ) 4 ] at 0 °C in mixtures of C 6 D 6 and bromobenzene polymerize 1-hexene at a rate that is first order in Zr and first order in 1-hexene with k p = 9.2 ± 0.7 M - 1 min - 1 and activation parameters Δ H ⧧ = 7.9 ± 0.4 kcal mol - 1 and Δ S ⧧ = −33.1 ± 1.1 cal mol - 1 K - 1 . The rate of polymerization decreases upon addition of dimethylaniline to the initiator and increases upon addition of [t-BuNON]ZrMe 2 to the initiator. In both circumstances, especially the latter, catalyst decomposition via β hydride elimination compromised the strictly living character of the polymerization.