Reversal of Polymerization Stereoregulation in Anionic Polymerization of MMA by Chiral Metallocene and Non-metallocene Initiators:  A New Reaction Pathway for Metallocene-Initiated MMA Polymerization

Synthesis and MMA polymerization of chiral ansa-zirconocene ester enolate complexes with C2- and Cs-ligation

“…In attempts to produce syndiotactic poly (methyl methacrylate), P(MMA), at least five research groups [5] have investigated the MMA polymerization using the C s -symmetric zirconocene dimethyl complex [Me 2 C(Cp)(Flu)]ZrMe 2 [6], in combination with borane or borate-based activators; however, they all found no polymerization activity. We reasoned that the inactivity of the derived methyl cation, [Me 2 C(Cp)(Flu)ZrMe] + , could simply be due to a problem with the initiation step that involves presumably an ineffective Zr-Me transfer to the coordinated monomer; hence, the active cationic ester enolate propagating species cannot be generated (Eq.…”

Synthesis and Reactivity of Oxametallacyclic Niobium Compounds by Using α,β‐Unsaturated Carbonyl Ligands

“…for 3a). The reactions were monitored by NMR spectroscopy which indicated formation of compounds MMA·E(C 6 F 5 ) 3 [15] as the only characterizable compounds. 19 Single-Crystal X-ray Structure Determination of Compounds 1a, 2a, 2c, and 10: Suitable yellow single crystals of 1a, 2a, 2c, and 10 for the X-ray diffraction study were selected ( Table 2).…”

“…[4,8,31] We have investigated the reactivity of complexes 2a-b and 3a-b with the Lewis acids E(C 6 F 5 ) 3 (E = B, Al) with the aim of abstracting the alkyl ligand to generate a cationic enolate compound, considering that early transition-metal derivatives of this type have been used as precursors for the catalytic polymerization of acrylates. [12][13][14][15][16] Although the nucleophilicity of the oxygen atom bonded to the niobium atom could compete with that of the carbon atom, we have previously observed that alkoxido complexes of the type [Cp*TaMe 3 (OR)] reacted with these Lewis acids E(C 6 F 5 ) 3 at the Ta-C bond. [32] Furthermore, Mashima and co-workers also reported that reaction of the MMA complex [TaCp*(DAD)(MMA)] [DAD = N(R) CH=CHN(R)] with AlMe 3 produced the activation of the Ta-C bond of the coordinated MMA ligand.…”

“…The study of enolate derivatives has attracted attention because they have been proposed as the active species for polymerization of polar monomers. [11][12][13][14][15][16] Another feature of these compounds is that coordination of the asymmetric α,β-unsaturated carbonyl ligands will create two new reactive points in the molecule at the M-C and M-O bonds.…”

Stereospecific Olefin Polymerization Catalyzed by Metallocene Complexes

“…The active species 49 is chiral at the Zr metal, and the triad distribution of the polymer was consistent with a catalyticsite control mechanism. Chen et al showed that stereoregularity greatly depends on co-catalysts: 44 and 46 with borane give isotactic poly(MMA) by catalytic-site control, while these catalysts with the alane Al(C 6 F 5 ) 3 give syndio-rich poly(MMA) by chainend control [144]. They achieved iso-b-syndio stereoblock poly(MMA) using the borane and the alane in one pot [145].…”