Cationic Zirconium Complexes that Contain Mesityl-Substituted Diamido/Donor Ligands. Decomposition via CH Activation and Its Influence on 1-Hexene Polymerization

Abstract

The dialkyl complexes [MesNMe]ZrMeNp (2b) and [MesNMe]ZrNp2 ([MesNMe]2- = [(MesNCH2CH2)2NMe]2-; Np = CH2CMe3) were prepared and shown to have distorted trigonal bipyramidal structures in which the two amido groups occupy equatorial positions. The neopentyl group in 2b was found in the axial position. Compound 2b was found to convert to another species (2a) in a first-order manner with k = 1.68 × 10-3 min-1 at 20 °C and to reach an equilibrium with Keq = [2a]/[2b] = 0.43 in C6D6. Activation of [MesNMe]ZrMeNp with [Ph3C][B(C6F5)4] led to formation of unobservable {[MesNMe]ZrNp}[B(C6F5)4], which decomposed by CH activation of an ortho mesityl methyl group to give an inactive dimer of {[activ-MesNMe]Zr}[B(C6F5)4], or in the presence of dimethylaniline by β methyl elimination to give {[MesNMe]ZrMe(PhNMe2)}[B(C6F5)4]. {[MesNMe]ZrMe}[B(C6F5)4] also decomposes to give the dimer of {[activ-MesNMe]Zr}[B(C6F5)4] with kd = 6.0 × 10-5 s-1 at 20 °C. A dimethyl complex was prepared that contained a second “internal amin...