Efficient Norbornene (NBE) Incorporation in Ethylene/NBE Copolymerization by Half-Titanocene Catalysts Containing Chlorinated Aryloxo Ligands

Aryl-Aryl Interactions in (Aryl-Perhalogenated) 1,2-Diaryldisilanes

Three 1,2-diaryltetramethyldisilanes X5 C6 -(SiMe2 )2 -C6 X5 with two C6 H5 , C6 F5 , or C6 Cl5 groups were studied concerning the importance of London dispersion driven interactions between their aryl groups. They were prepared from 1,2-dichlorotetramethyldisilane by salt elimination. Their structures were determined in the solid state by X-ray diffraction and for free molecules by gas electron-diffraction. The solid-state structures of the fluorinated and chlorinated derivatives are dominated by aryl-aryl interactions. Unexpectedly, Cl5 C6 -(SiMe2 )2 -C6 Cl5 exists exclusively as an eclipsed syn-conformer in the gas phase with strongly distorted Si-C6 Cl5 units due to strong intramolecular interactions. In contrast, F5 C6 -(SiMe2 )2 -C6 F5 reveals weaker interactions. The contributions to the total interaction energy were analyzed by SAPT calculations.

Optically Transparent Functional Polyolefin Elastomer with Excellent Mechanical and Thermal Properties

Synthesis of a variety of optically transparent polyolefin elastomers consisting of hard segment of polynorbornene and several kinds of soft segments such as atactic polypropylene, poly(ethylene-co-propylene), and poly(ethylene-co-1-hexene) was achieved. The block copolymers exhibited excellent toughness and thermal property with efficient elastic recovery. Most importantly, the introduction of hydroxyl group into polynorbornene segment not only modulated surface property of block copolymers, but also improved their mechanical properties.

Multicomponent Mechanochemical Synthesis of Cyclopentadienyl Titanium tert-Butoxy Halides, Cp x TiX y (O t Bu)4-(x+y) (x, y = 1, 2; X = Cl, Br)

Titanium tert-butoxy halides of the formula Cp _x TiX _y (O ^t Bu)_4-(x+y) (x, y = 1, 2; X = Cl, Br) have been prepared thorough milling the reagents without solvent. In the case of the chloride derivatives, Cp₂TiCl₂ is used as a starting material; in the case of the bromides, a mixture of LiCp, TiBr₄, and Li[O ^t Bu] is used. The stoichiometric ratios of the starting materials are reflected in the major products of the reactions. Single-crystal X-ray structures are reported for Cp₂TiCl(O ^t Bu), Cp₂TiBr(O ^t Bu), and CpTiBr₂(O ^t Bu), as well as for Cp₂TiCl(O ⁱ Pr) and a redetermination of Cp₂TiCl(OMe). The tert-butoxy derivatives are notable for their nearly linear Ti-O-C angles (>170°) that reflect Ti-O π-bonding, an interpretation supported with density functional theory calculations.

Efficient control of ethylene–norbornene copolymerization behavior of a fluorenylamido-ligated titanium complex: substituent effects of the amido ligand and copolymer properties

Copolymerization behavior of ethylene and norbornene was controlled using a (fluorenyl)(amido)titanium complex bearing a cumyl-amido ligand.

Kinetics, Mechanism and Theoretical Studies of Norbornene-Ethylene Alternating Copolymerization Catalyzed by Organopalladium(II) Complexes Bearing Hemilabile α-Amino-pyridine

Cationic methylpalladium complexes bearing hemilabile bidentate α-amino-pyridines can serve as effective precursors for catalytic alternating copolymerization of norbornene (N) and ethylene (E), under mild conditions. The norbornyl palladium complexes in the formula of {[RHNCH₂(o-C₆H₄N)]Pd(C₇H10Me)(NCMe)}(BF₄) (R = iPr (2a), tBu (2b), Ph (2c), 2,6-Me₂C₆H₃ (2d), 2,6-iPr₂C₆H₃ (2e)) were synthesized via single insertion of norbornene into the corresponding methylpalladium complexes 1a-1e, respectively. Both square planar methyl and norbornyl palladium complexes exhibit facile equilibria of geometrical isomerization, via sterically-controlled amino decoordination-recoordination of amino-pyridine. Kinetic studies of E-insertion, N-insertion of complexes 1 and 2, and the geometric isomerization reactions have been examined by means of VT-NMR, and found in excellent agreement with the results estimated by DFT calculations. The more facile N-insertion in the cis-isomers, and ready geometric isomerization, cooperatively lead to a new mechanism that accounts for the novel catalytic formation of alternating COC.

Synthesis and structural analysis of aryloxo-modified trinuclear half-titanocenes, and their use as catalyst precursors for ethylene polymerisation

The synthesis and structural analysis of aryloxo-modified trinuclear half-titanocenes have been explored: the Cp* analogues showed higher activities for ethylene polymerisation than the related mononuclear analogues.