Syndiospecific Polymerization of o-Methoxystyrene and Its Silyloxy or Fluorine-Substituted Derivatives by HNC-Ligated Scandium Catalysts: Synthesis of Ultrahigh-Molecular-Weight Functionalized Polymers

Abstract

A scandium dication active species [(IPr)­Sc­(μ-CH2SiMe3)­(μ-CH2CHMe2)­Al i Bu2]2+[B­(C6F5)4]2 – (IPr = (2,6-C6H3 i Pr2NCH)2C) in situ generated from the reaction of an N-heterocyclic carbene-ligated scandium trialkyl complex (IPr)­Sc­(CH2SiMe3)3 (2) with 1–3 equiv of cocatalyst [Ph3C]­[B­(C6F5)4] and an excess of Al i Bu3 exhibits unprecedentedly high activity (up to 2.2 × 106 g·molSc –1·h–1) and syndiotactic selectivity (rrrr > 99%) in the polymerization of o-methoxystyrene (oMOS) and its silyloxy- or fluorine-substituted derivatives, affording syndiotactic poly­(oMOS)­s and their silyloxy or fluorine-substituted derivatives with ultrahigh molecular weight (M n up to 4.6 × 106) and moderate molecular weight distributions (M w/M n = 1.37–2.21) unavailable by the traditional catalysts. Based on in situ NMR spectroscopy, matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) spectroscopy, and density functional theory (DFT) calculations, a plausible coordination polymerization mechanism has been proposed for the syndiotactic polymerization of oMOS by such a Sc dication active species.

Polar Molecules Regulating the Regio‐ and Stereoselectivity of Polymerization of Conjugated Dienes Catalyzed by CGC‐Type Rare‐Earth Metal Catalysts

“…of Ph 3 CCH 2 SiMe 3 and Ph 3 CH (Figure S10d, Supporting Information). [14] Then 10 equiv. of PhOMe was added to the above reaction.…”

Three Different Types of Asymmetric Polymerization of Aryl Isocyanides by Using Simple Rare-Earth Metal Trialkyl Precursors

“…The different reaction performances of the complexes 1 – 3 and 4 – 6 had been identified by the in situ 1 H NMR spectra (Figures S7–S10). This phenomenon was consistent with our previous work and was also reported by some studies, though the reason is unclear so far. , …”

“…This phenomenon was consistent with our previous work and was also reported by some studies, though the reason is unclear so far. 41,43 To realize the multiple helical sense control of PIs, different asymmetric polymerizations of aryl isocyanides were implemented by using different cationic active species in situ generated from the complexes 1−6/cocatalyst binary systems under mild conditions. The representative results are summarized in Tables 1−4.…”

Stereoselective Polymerization of Aromatic Vinyl Polar Monomers

“…of cocatalyst [Ph 3 C][B(C 6 F 5 ) 4 ] and Al i Bu 3 exhibits high activity (up to 16020 h −1 ) and syndiotactic selectivity ( rrrr >99 %) in the polymerization of M3 (Table 8, Runs 14 and 15). The polymerization of silyloxy(and fluorine)‐substituted derivatives (M13–M18) (Scheme 1) by complex 96 /[Ph 3 C][B(C 6 F 5 ) 4 ]/Al i Bu 3 system also produced syndiotactic polymer with rrrr of 54 % ∼99 % [33] . In 2016, Cui and Wan et al.…”

“…The polymerization of silyloxy(and fluorine)-substituted derivatives (M13-M18) (Scheme 1) by complex 96/[Ph 3 C][B(C 6 F 5 ) 4 ]/ Al i Bu 3 system also produced syndiotactic polymer with rrrr of 54 % ~99 %. [33] In 2016, Cui and Wan et al achieved controlled isoselective polymerization of the monomer M9 using complex 97 with co-activation of [Ph 3 C][B(C 6 F 5 ) 4 ] and Al( i Bu) 3 to obtain syndiotactic polymers with rrrr greater than 99 %. The polymers were all crystalline polymers with T m > 300 °C.…”