Six-coordinated dibenzyl Zr complex bearing an [OSSO]-type tetradentate ligand was synthesized, and the structure was fully characterized by NMR spectroscopy and X-ray crystallography. The zirconium complex has C(2) symmetry in solution. Owing to an effect of the cyclooctane ring structure, the combination of the zirconium complex and B(C(6)F(5))(3) or (Ph(3)C)[B(C(6)F(5))(4)] as the activator exhibited high activity toward polymerization of 1-hexene to yield highly isotactic poly(1-hexene).
Group
5 metal complexes bearing an [OSSO]-type bis(phenolate) ligand
have been successfully prepared by the reaction of a bis(phenol) compound 3 or its dilithio salt 6 with VO(OPr)3, NbCl5, or TaCl5. X-ray crystallographic analyses
revealed the monomeric nature of the resulting complexes, [OSSO]VO(OPr)
(5), [OSSO]NbCl3 (7), and [OSSO]TaCl3 (8), where the metal centers adopted cis-α
configurations of the [OSSO] tetradentate ligand. The tantalum(V)
complex 8 with
i
Bu3Al/(Ph3C)[B(C6F5)4] as
an activator catalyzed the polymerization of 1-hexene to provide completely
isotactic poly(1-hexene), with a narrow molecular weight distribution
([mmmm] > 95%, M
w =
9100
g mol–1, PDI = 1.6); this is the first group 5 metal
catalyst for α-olefin polymerization to afford a highly isospecific
polymer.
trans-Cyclooctanediyl-bridged [OSSO]-type ligand 4 reacts with TiCl(4)(thf)(2) in toluene to produce the corresponding titanium(IV) dichloro complexes as an inseparable mixture of cis-α isomer 6a and cis-β isomer 6b in a ratio of 2:1, whereas treatment of dilithio salt of 4 with TiCl(3)(thf)(3) in Et(2)O afforded chloride-bridged dimeric titanium(III) complex 8, which indicated the antiferromagnetic character in a nonpolar solvent solution. Di(isopropoxy) titanium(IV) complex 10 having a C(2)-symmetric cis-α configuration was synthesized by the reaction of 4 with Ti(O(i)Pr)(4) in toluene as yellow crystals. Moreover, the reaction of 4 with Ti(NEt(2))(4) in toluene resulted in the unexpected formation of [OSSO]-type bis(phenolato)-bridged dinuclear diamido titanium(IV) complex 11, which adopted a distorted tetrahedral geometry on the titanium center. These titanium complexes were characterized on the basis of their NMR spectroscopic data, and the molecular structures of complexes 8, 10, and 11 were established by single crystal X-ray diffraction. The titanium(IV) and (III) complexes 6 and 8 upon activation with a cocatalyst in toluene polymerized 1-hexene isospecifically to produce poly(1-hexene) having high molecular weight (M(w) = 22,000-52,000 g mol(-1)) and relatively narrow polydispersity (M(w)/M(n) = 1.7-1.8), albeit with low activity [0.27-1.0 g mmol(cat)(-1) h(-1)].
Lithium-ion batteries LIB have been used as power sources of portable electronic devices such as a laptop computer, a celler phone, and so on 1 , 2 . Moreover, LIBs have been expected as power sources of hybrid electric vehicle, plug-in hybrid electric vehicle, and electric vehicle due to their high energy densities.High rate performance, safety, and longer life of LIBs are required for practical use in these EVs. Among the above requirements, we have focused on the rate capabilities of carbonaceous negative electrodes.The rate capabilities of LIBs can be enhanced by the decrease of internal resistances caused by lithium-ion diffusion in active materials and electrolyte, lithium-ion transfer at interface between electrode and electrolyte, electron transfer at interface between current collector and electrode. These processes can be a rate-determining step. At
Molecular aggregation structure and mechanical as well as thermal properties of novel well-defined multiblock copolymers consisting of crystalline syndiotactic polystyrene (sPS) and rubbery hydrogenated polyisoprene (hPIp) were investigated. The morphology and crystalline ordered structure of the multiblock copolymer films prepared by solvent casting from 1,2-dichlorobenzene solution depended on the volume fraction of sPS (VF sPS ) and number of blocks. The multiblock copolymer films exhibited ordered morphology with low crystallinity. The crystallinity of the sPS reduced with decreasing the VF sPS . The pentablock copolymer produced more ordered morphology and less crystallinity than the triblock copolymers. The anisotropic orientation and mechanical stability of the δ form sPS crystals in the spherical sPS domains during uniaxial stretching were demonstrated. Tensile testing and dynamic mechanical analysis indicated that these multiblock copolymer films with appropriate sPS fraction are strong, tough, and elastic and thus could be potential candidates for a new type of thermoplastic elastomer with discrete crystalline hard domains.
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