A series of chiral mononuclear dialkyl
complexes [(S,S)-BOPA]Ln(CH2SiMe3)2 (1, 2) (BOPA = (S,S)-bis(oxazolinylphenyl)amido;
Ln = Sc (1); Ln = Lu (2)) and binuclear
alkyl complexes [ο-(S)-OPA–C6H4–(CH2SiMe3)CN–CH(
i
Pr)CH2–O]Ln(CH2SiMe3)}2 (3,
4) (OPA = (oxazolinylphenyl)amine; Ln = Y (3);
Ln = Tm (4)) have been synthesized in moderate yields
via one-pot acid–base reactions by use of the tris(trimethylsilylmethyl)
rare earth metal complexes with the chiral tridentate (S,S)-bis(oxazolinylphenyl)amine ligand. In the presence
of activator with or without a small amount of Al
i
Bu3, the dialkyl complexes 1 and 2 exhibit very high activities (up to 6.8 × 105 g molLn
–1 h–1) and trans-1,4-selectivity (up to 100%) in the quasi-living polymerization
of isoprene, yielding the trans-1,4-PIPs with moderate
molecular weights (M
n = (0.2–1.0)
× 105 g/mol) and narrow molecular weight distributions
(M
w/M
n = 1.02–2.66).
The air/water-tolerant chiral Pd alkyl complexes/borate systems promote the norbornene polymerization both in air and water using unpretreated technical grade solvent and monomer with extremely high activity up to 1.7 × 109 g PNB per molPd per h.
A series of chiral palladium(II) and nickel(II) complexes bearing a C 2 -symmetric monoanionic tridentate bis(oxazoline) ligand, (R 2 -(S,S)-BOZ)M(X) (1−6: R = CH- 6)), have been synthesized and structurally characterized. The experimental results demonstrate that such chiral palladium-(II) and nickel(II) complexes bearing C 2 -symmetric tridentate ligands in which the monoanionic group is located inside are effective for norbornene polymerization. In the presence of various cocatalysts such as MAO, MMAO, and activator/AlR 3 , these chiral palladium(II) complexes exhibit much higher activities of up to 4.8 × 10 8 g of PNB (mol of Pd) −1 h −1 for the vinylic polymerization of norbornene, affording insoluble polynorbornenes with high packing density. In contrast, the chiral nickel(II) complexes show relatively low activities of ca. 4.5 × 10 7 g of PNB (mol of Ni) −1 h −1 and produce both insoluble polynorbornenes and soluble high-molecular-weight polynorbornenes with moderate molecular weight distributions.
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