Norio Nakata

Completely Isospecific Polymerization of 1-Hexene Catalyzed by Hafnium(IV) Dichloro Complex Incorporating with an [OSSO]-type Bis(phenolate) Ligand

In the presence of dried methylaluminoxane as an activator, the hafnium(IV) dichloro pre-catalyst 4 incorporating with an [OSSO]-type ligand was found to promote precisely isospecific 1-hexene polymerizations of [mmmm] up to 95xa0% with fairly high activities (1,050–3,180xa0gxa0mmol(4)−1xa0h−1) and relatively narrow polydispersities (Mw/Mnxa0=xa01.5–1.8).

Extremely active α-olefin polymerization and copolymerization with ethylene catalyzed by a dMAO-activated zirconium(IV) dichloro complex having an [OSSO]-type ligand

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 = 40u2006000–150u2006000 g mol−1). The corresponding activity was recorded with quite high values up to 18u2006100 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 = 7000–21u2006300 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 = 10u2006100–17u2006300 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.

Red and Near-Infrared Photoluminescence of D-π-A-Type Compounds Based on a 1,4-Diaryl-1-thio-1,3-butadiene Conjugated System in a Dibenzobarrelene Skeleton

1,4-Diaryl-1-thio-1,3-butadiene derivatives having a π-donor dimethylamino group and several π-acceptor substituents at both terminals of the conjugated system were synthesized by intramolecular [4 + 2] cycloaddition of 1-thio-enynes and subsequent chemical transformations. They displayed largely red-shifted absorption and emission spectra in solution, the powder state, and in polymer films. The derivatives with a 2,2-dicyanoethenyl group as the π-acceptor exhibited inverted solvatochromism in both optical absorption and fluorescence spectroscopies.

Highly Isospecific Polymerization of Silyl-Protected ω-Alkenols Using an [OSSO]-Type Bis(phenolato) Dichloro Zirconium(IV) Precatalyst.

The coordination polymerization of silyl-protected ω-alkenols such as ω-alken-α-oxytriisopropylsilanes 1 provides poly(ω-alkenyl-α-oxytriisopropylsilalne)s with a highly isospecific microstructure ([mmmm] > 95%) when a combination of [OSSO]-type bis(phenolato) dichloro zirconium(IV) complex 2 and dried methylaluminoxane is used as the precatalyst and activator, respectively. The resulting siloxy-substituted polymers could be efficiently transformed into the corresponding functionalized polyolefins, which contained up to 90% acetyl groups and ≈7% hydroxy groups in the terminal side chains.

Synthesis of 4-Chalcogeno-1-aza-1,3-butadiene Derivatives by Intramolecular Cyano-Diels–Alder Reaction and Borane-Coordination-Induced Fluorescence Enhancement

4-Thio-1-aza-1,3-butadiene derivatives 3 incorporating a rigid dibenzobarrelene skeleton were synthesized by the intramolecular cyano-Diels-Alder reaction of 9-anthryl cyanoethenyl sulfides 6. The thermal reaction of 6 afforded an equilibrium mixture of 3 and 6, but the cyclization was effectively promoted by the addition of BF3·Et2O or B(C6F5)3 to yield imine-borane adducts 8 and 9. The imine-borane adducts emit intense blue fluorescence both in solution and in the crystalline state. This is in stark contrast to free imines 3, which are weakly fluorescent. Selenium analogue 4 and N-oxide 12 of 3a were synthesized, along with their B(C6F5)3 adducts.

Highly Active and Isospecific Styrene Polymerization Catalyzed by Zirconium Complexes Bearing Aryl-substituted [OSSO]-Type Bis(phenolate) Ligands

[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%.

Enantio- and Stereoselective Cyclopolymerization of Hexa-1,5-diene Catalyzed by Zirconium Complexes Possessing Optically Active Bis(phenolato) Ligands.

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).