CH Bond Activation in Cations of the Type {[(2,4,6-Me₃C₆H₂NCH₂CH₂)₂NMe]ZrR}⁺ and a Simple Solution that Yields a Catalyst for the Living Polymerization of 1-Hexene

Abstract

{[(MesNCH 2 CH 2 ) 2 NMe]ZrMe}[B(C 6 F 5 ) 4 ] and intermediates in the polymerization reaction of 1-hexene that are formed from it decompose as a consequence of CH activation in an ortho methyl group in the mesityl substituent. The intermediates in the polymerization reaction decompose significantly more readily than does {[(MesNCH 2 CH 2 ) 2 NMe]ZrMe}[B(C 6 F 5 ) 4 ]. On the other hand, analogous cationic complexes that contain the [(2,6-Cl 2 C 6 H 3 NCH 2 CH 2 ) 2 NMe] 2ligand are relatively stable and will consume 1-hexene in a strictly first-order and apparently living manner at 0 °C in chlorobenzene.

Catalysts for the Living Insertion Polymerization of Alkenes: Access to New Polyolefin Architectures Using Ziegler–Natta Chemistry

“…A similar decomposition pathway of a cationic zirconium complex through CH bond activation of an adjacent methyl group had previously been uncovered by Horton and co‐workers in a structurally related triamido system 108. A simple change in aryl substitution from 2,4,6‐trimethylphenyl to 2,6‐dichlorophenyl prevented CH activation of the ligand, and a living 1‐hexene polymerization catalyst precursor 29 b was obtained 103. The polymer generated with catalyst 29 b /[Ph 3 C][B(C 6 F 5 ) 4 ] at 0 °C was of higher molecular weight than that produced with the NON catalysts 28 ( M n up to 79 000 g mol −1 ), while the molecular weight distribution of the polymer remained extremely narrow ( M w / M n , 1.01–1.04).…”

“…Activation of 29 a with [Ph 3 C][B(C 6 F 5 ) 4 ] and subsequent reaction with 1‐hexene led to the formation of poly(1‐hexene) which displayed limited average molecular weight and broader molecular weight distribution than the polymer obtained with the NON system 28 . Subsequent studies revealed that this non‐living behavior was caused by catalyst decomposition by CH activation of one of the mesityl o ‐methyl substituents, producing a dimeric decomposition product that was characterized by X‐ray crystallography (Scheme ) 103. A similar decomposition pathway of a cationic zirconium complex through CH bond activation of an adjacent methyl group had previously been uncovered by Horton and co‐workers in a structurally related triamido system 108.…”

Katalysatoren für die lebende Insertionspolymerisation von Alkenen: mit Ziegler-Natta-Chemie zu neuartigen Polyolefin-Architekturen

“…[ 3 verhinderte Ket-ten¸bertragungen und f¸hrte zu einer lebenden Polymerisation von 1-Hexen und hˆheren a-Olefinen (Schema 16). [103] Eine ‰hnliche Zersetzung 4 ] 31 (R Et, nBu, iBu, nPr, iPr). In CH 2 Cl 2 als Lˆsungsmittel war die katalytische Aktivit‰t drastisch hˆher, und es wurden hochmolekulare ataktische Polymere (M n > 120 000 g mol À1 ) mit engen Molekulargewichtsverteilungen (M w /M n 1.07) erhalten.…”

Tridentate ligands and beyond in group IV metal α-olefin homo-/co-polymerization catalysis

“…Indeed, cationic complexes containing the ligand set (2,6-Cl 2 C 6 H 3 NCH 2 CH 2 ) 2 NMe] 2À were found to be fairly stable (e.g., hours at 0 1C), and polymerized 1-hexene in a living manner (0 1C, chlorobenzene). [72][73][74] Asymmetric variations of this type of diamide N-donor ligand set have been synthesized (see XXVIII, Fig. 48, left), which contained ethylene/o-phenylene arms.…”