Tomoyuki Toda
Saitama University
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Featured researches published by Tomoyuki Toda.
Journal of the American Chemical Society | 2009
Tomoyuki Toda; Norio Nakata; Tsukasa Matsuo
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).
Polymer Chemistry | 2011
Norio Nakata; Tomoyuki Toda
Several recent efforts concerning post-metallocene Group 4 metal complexes incorporating mixed donor [OSSO]-type tetradentate bis(phenolato) ligands are reviewed. These [OSSO]-type ligands can be mainly classified as 5–5–5, 5–6–5 and 6–5–6 arrays of chelate rings toward central metals. As the main topics are described the design and unique coordination chemistry of the [OSSO]-type ligands and catalytic activities of the resultant titanium, zirconium, and hafnium complexes as single-site catalysts for polymerizations and copolymerizations of olefins.
Inorganic Chemistry | 2012
Norio Nakata; Tomoyuki Toda; Tsukasa Matsuo
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)].
RSC Advances | 2015
Tomoyuki Toda; Norio Nakata; Tsukasa Matsuo
The ability of a zirconium(IV) dichloro complex (6b) incorporating an [OSSO]-type ligand 5 with dMAO as an activator for the polymerization of 1-hexene and 4-methyl-1-pentene (4-MP) is described. In the polymerization of 1-hexene, the combination of the 6b/dMAO catalyst system efficiently provided poly(1-hexene)s with completely isotactic [mmmm] pentad more than 95% and relatively large molecular weight (Mw = 40 000–150 000 g mol−1). The corresponding activity was recorded with quite high values up to 18 100 g mmol(6b)−1 h−1, which increased significantly compared with those of the related non-Cp complexes. The polymerization of 4-MP using the 6b/dMAO system at different temperatures also gave perfect isotactic poly(4-MP)s ([mmmm] > 95%) with moderate molecular weights (Mw = 7000–21 300 g mol−1), relatively narrow polydispersities (Mw/Mn = 1.5–1.7), and activities of 1220–1690 g mmol(6b)−1 h−1. This catalyst system was also found to promote ethylene copolymerization with different amounts of 1-hexene at 25 °C under atmospheric pressure producing random ethylene/1-hexene copolymers (Mw = 10 100–17 300 g mol−1, Mw/Mn = 1.8–1.9, 1-hexene contents = 37.3–66.7 mol%) with fairly high activity up to 2700 g mmol(6b)−1 h−1.
Phosphorus Sulfur and Silicon and The Related Elements | 2011
Tomoyuki Toda; Norio Nakata; Tsukasa Matsuo
Abstract An [OSSO]-type tetradentate ligand was prepared starting from trans-cyclooctane-1,2-dithiol. Hexacoordinated dibenzyl Zr complex was synthesized by the reaction of the ligand with Zr(CH2Ph)4 and its structure was fully characterized by nuclear magnetic resonance (NMR) spectroscopy and X-ray crystallography. The zirconium complex has the C2 symmetry in solution. The zirconium complex activated with B(C6F5)3 or (Ph3C)[B(C6F5)4] provided a highly active catalytic system for coordinate polymerization of 1-hexene to yield poly(1-hexene)s with high isospecificity.
Polymers | 2016
Norio Nakata; Tomoyuki Toda; Yusuke Saito; Takanori Watanabe
[OSSO]-type dibenzyl zirconium(IV) complexes 9 and 10 possessing aryl substituents ortho to the phenoxide moieties (ortho substituents, phenyl and 2,6-dimethylphenyl (Dmp)) were synthesized and characterized. Upon activation with dMAO (dried methylaluminoxane), complex 9 was found to promote highly isospecific styrene polymerizations ([mm] = 97.5%–99%) with high molecular weights Mw up to 181,000 g·mmol−1. When the Dmp-substituted pre-catalyst 10/dMAO system was used, the highest activity, over 7700 g·mmol(10)−1·h−1, was recorded involving the formation of precisely isospecific polystyrenes of [mm] more than 99%.
Macromolecular Rapid Communications | 2016
Norio Nakata; Takanori Watanabe; Tomoyuki Toda
Enantio- and stereoselective cyclopolymerization of hexa-1,5-diene was achieved by enantiomerically pure dichloro zirconium(IV) pre-catalysts 2 possessing chiral [OSSO]-type bis(phenolate) ligands (-)-1 and (+)-1 in combination with dried methylaluminoxane (dMAO) as an activator. The corresponding activities were recorded with quite high values up to 1,960 g mmol(2)-1 h-1 , which are extremely larger than those of the related complexes. The microstructure analysis for the PMCPs furnished by pre-catalysts (Λ,S,S)-2 and (Δ,R,R)-2 showed good isotacticity factors (α = 75-78%) and relatively high proportions of trans-cyclopentane rings (σ = 14-21%). These enantiomeric PMCPs exhibited large specific optical rotations ([α]D = +28 to +32° from (Λ,S,S)-2, -26 to -34° from (Δ,R,R)-2).
Macromolecules | 2013
Norio Nakata; Tomoyuki Toda; Tsukasa Matsuo
Journal of Organometallic Chemistry | 2011
Tomoyuki Toda; Norio Nakata; Tsukasa Matsuo
ACS Catalysis | 2013
Tomoyuki Toda; Norio Nakata; Tsukasa Matsuo