Rare‐earth‐metal‐initiated polymerizations of (meth)acrylates and block copolymerizations of olefins with polar monomers

Abstract

The organo-rareearth-metal-initiated living polymerization of methyl methacrylate (MMA) was first discovered in 1992 with (C 5 Me 5 ) 2 LnR (where R is H or Me and Ln is Sm, Yb, Y, or La) as an initiator. These polymerizations provided highly syndiotactic (Ͼ96%) poly(methyl methacrylate) (PMMA) with a high number-average molecular weight (M n Ͼ 1000 ϫ 10 3 ) and a very narrow molecular weight distribution [weight-average molecular weight/number-average molecular weight (M w /M n ) Ͻ 1.04] quantitatively in a short period. Bridged rare-earth-metallocene derivatives were used to perform the block copolymerization of ethylene or 1-hexene with MMA, methyl acrylate, cyclic carbonate, or ⑀-caprolactone in a voluntary ratio. Highly isotactic (97%), monodisperse, high molecular weight (M n Ͼ 500 ϫ 10 3

Genuine Heteroleptic Complexes of Early Rare‐Earth Metals: Synthesis, X‐ray Structure, and Their Use for Stereospecific Isoprene Polymerization Catalysis

“…Unfortunately, in both cases, a sticky paste was obtained as the product of the reaction, and the elemental analyses were not satisfactory. 3 Sm] were also present. [42] Diamagnetic diketimine signals were also detected.…”

“…We realized that this was not a good strategy because the formation of homoleptic [{(ptol)NN} 3 [32] We had previously obtained monocyclopentadienyl derivatives of Nd and Sm by a simple metathetic reaction of the inorganic precursors [LnX 3 (thf) 3 ] (X = Cl or BH 4 ) with the bulky Cp*' À ion. [33] These derivatives could be convenient starting materials to afford the expected heteroleptic cyclopentadienyldiketiminato complexes in a second step (Scheme 1).…”

“…Polymerization experiments: It was shown very recently that the trivalent pseudo-halide complex [Nd(BH 4 ) 3 (thf) 3 ] is an efficient initiator for the ring-opening polymerization of e-caprolactone. The monomer first inserts into the NdÀ H(BH 3 ) bond, then propagation occurs via the resulting alkoxy moiety.…”

“…We conducted preliminary syntheses from the soluble borohydrides on the NMR scale with deuterated benzene (THF is necessary, at least in the first step, if chlorides are chosen as the starting material 3 ] by successive substitutions of the chloride ligands with (C 5 Me 4 iPr)Na, then with NaBH 4 . [36] ½Cp * 0 LnðBH 4 Þ 2 ðthfÞ n þ Kfðp-tolÞNNg…”

Synthesis, structure characterization and catalytic activity of lanthanide complexes containing an ansa carbonous‐bridged cyclopentadienyl—thienyl ligand

“…According to the reports, [21,22] the reaction of RCp 2 LnCl reaction with NaH gave RCp 2 LnH, and the organolanthanide hydride showed high catalytic activity for the polymerization of polar monomers or non-polar monmers. [23] In the system [cyclo-C 4 H 3 SC(Me) 2 2 was formed as an active center, which has been proved by 1 H NMR and X-ray diffraction study in a similar system. [24] In addition, the different trend in influence of the center ionic radius on the catalytic activity supported the hyposthesis that the different active species formed in the catalytic system [cyclo-C 4 H 3 SC(Me) 2 3 , the combination of a sterically bulky ligand with a small metal center is of benefit to form a more unsymmetric η 5 coordination of the five-membered ring as well as to stabilize active centers.…”