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).

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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)].

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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

Treatment of trans-cyclooctanediyl-bridged [OSSO]-type ligand 1 with Hf­(CH2Ph)4 in toluene afforded the corresponding hafnium­(IV) dibenzyl complex 5 as pale yellow crystals. X-ray crystallographic analysis of 5 revealed that the six-coordinated hafnium center incorporated in the [OSSO]-type ligand 1 adopted cis-α configuration, and two benzyl ligands were coordinated to hafnium center by η1-fashion. In the polymerization of 1-hexene, the combination of hafnium complex 5 and B­(C6F5)3, (Ph3C)­[B­(C6F5)4], or dMAO (dried methylaluminoxane) as an activator provided poly­(1-hexene)­s with perfect isotacticity ([mmmm] > 95%) and high molecular weights (M w = 74 800–421 000 g mol–1). The combination of 5/dMAO catalyst system, in particular, exhibited fairly high activity of 2100 g mmol (5)−1 h–1, which is quite higher than those of previously reported [OSSO]-type hafnium complexes. In addition, the polymerization of 4-methyl-1-pentene (4-MP) catalyzed by the 5/(Ph3C)­[B­(C6F5)4] system at room temperature produced completely isotactic poly­(4-MP)­s with good activity (54–101 g mmol (5)−1 h–1) and relatively narrow PDI (M w/M n = 1.3). Furthermore, the propylene polymerization catalyzed by the 5/dMAO system at different temperatures (0–70 °C) for 1 h afforded highly isotactic polypropylenes, where the catalyst activity and isotacticity depend on the polymerization temperature. Thus, the activity greatly increased from 500 to 17 000 g mmol (5)−1 h–1 when the polymerization temperature was increased. In contrast, isotacticity and melting transition temperature (T m) were elevated by decreasing polymerization temperature (at 0 °C: [mmmm] = 93.7%, T m = 156.2 °C; at 70 °C: [mmmm] = 86.8%, T m = 140.9 °C).