The incorporation of 5‐vinyl‐2‐norbornene (VNB) into ethylene‐norbornene copolymer was investigated with catalysts [Ph2C(Fluo)(Cp)]ZrCl2 ( 1 ), rac‐[Et(Ind)2]ZrCl2 ( 2 ), and [Me2Si(Me4Cp)tBuN]TiCl2 ( 3 ) in the presence of MAO by terpolymerizing different amounts of 5‐vinyl‐2‐norbornene with constant amounts of ethylene and norbornene at 60°C. The highest cycloolefin incorporations and highest activity in terpolymerizations were achieved with 1 . The distribution of the monomers in the terpolymer chain was determined by NMR spectroscopy. As confirmed by XRD and DSC analysis, catalysts 1 and 3 produced amorphous terpolymer, whereas 2 yielded terpolymer with crystalline fragments of long ethylene sequences. When compared with poly‐(ethylene‐co‐norbornene), VNB increased both the glass transition temperatures and molar masses of terpolymers produced with the constrained geometry catalyst whereas decreased those for the metallocenes. 相似文献
The synthesis of a series of ansa‐titanocene dichlorides [Cp′2TiCl2] (Cp′=bridged η5‐tetramethylcyclopentadienyl) and the corresponding titanocene bis(trimethylsilyl)acetylene complexes [Cp′2Ti(η2‐Me3SiC2SiMe3)] is described. The ethanediyl‐bridged complexes [C2H4(C5Me4)2TiCl2] ( 2 ‐Cl2) and [C2H4(C5Me4)2Ti(η2‐Me3SiC2SiMe3)] ( 2‐ btmsa; btmsa=η2‐Me3SiC2SiMe3) can be obtained from the hitherto unknown calcocenophane complex [C2H4(C5Me4)2Ca(THF)2] ( 1 ). Furthermore, a heterodiatomic bridging unit containing both, a dimethylsilyl and a methylene group was introduced to yield the ansa‐titanocene dichloride [Me2SiCH2(C5Me4)2TiCl2] ( 3 ‐Cl2) and the bis(trimethylsilyl)acetylene complex [Me2SiCH2(C5Me4)2Ti(η2‐Me3SiC2SiMe3)] ( 3 ‐btmsa). Besides, tetramethyldisilyl‐ and dimethylsilyl‐bridged metallocene complexes (structural motif 4 and 5 , respectively) were prepared. All ansa‐titanocene alkyne complexes were reacted with stoichiometric amounts of water; the hydrolysis products were isolated as model complexes for the investigation of the elemental steps of overall water splitting. Compounds 1 , 2 ‐btmsa, 2 ‐(OH)2, 3 ‐Cl2, 3 ‐btmsa, 4 ‐(OH)2, 3 ‐alkenyl and 5 ‐alkenyl were characterised by X‐ray diffraction analysis. 相似文献
Ethylene-propene copolymerization was carried out with Cp2MCl2 (Cp = cyclopentadienyl), rac-Et(Ind)2MCl2, rac-Me2Si(Ind)2MCl2 (Et = ethylene, Me2Si = dimethylsilyl, Ind = indenyl, M = Zr or Hf)/methylaluminoxane. In the case of using ansa-hafnocenes, the minimum molecular size (extended chain length) of ethylene-propene copolymer was obtained at about 50 mol-% of propene content in the copolymer. The polymerization activity decreased with increase of propene feed ratio in non-bridged non-specific metallocenes. Higher polymerization activities were observed for the copolymerization compared to ethylene and propene homo-polymerization with ansa-isospecific metallocenes. The factor of molecular size lowering was studied by the chain propagation and chain transfer reaction. 相似文献
The three title compounds tri‐μ‐carbonyl‐1:2κ2C;1:3κ2C;2:3κ2C‐octacarbonyl‐1κC,2κ2C,3κ2C,4κ3C‐η5‐methylcyclopentadienyl‐tetrahedro‐triiridiummolybdenum(3 Ir—Ir)(3 Ir—Mo), tri‐μ‐carbonyl‐1:2κ2C;1:3κ2C;2:3κ2C‐octacarbonyl‐1κC,2κ2C,3κ2C,4κ3C‐η5‐tetramethylcyclopentadienyl‐tetrahedro‐triiridiummolybdenum(3 Ir—Ir)(3 Ir—Mo) and tri‐μ‐carbonyl‐1:2κ2C;1:3κ2C;2:3κ2C‐octacarbonyl‐1κC,2κ2C,3κ2C,4κ3C‐η5‐pentamethylcyclopentadienyl‐tetrahedro‐triiridiummolybdenum(3 Ir—Ir)(3 Ir—Mo), [MoIr3(η5‐C5H5?nMen)(μ‐CO)3(CO)8], where n = 1, 4 or 5, have a pseudotetrahedral MoIr3 core geometry, with a η5‐C5H5?nMen group ligating the Mo atom, bridging carbonyls spanning the edges of an MoIr2 face, and eight terminally bound carbonyls. 相似文献
The reactions of the Group 4 metallocene alkyne complexes rac‐(ebthi)M(η2‐Me3SiC2SiMe3) ( 1 a : M=Ti, 1 b : M=Zr; rac‐(ebthi)=rac‐1,2‐ethylene‐1,1′‐bis(η5‐tetrahydroindenyl)) with Ph?C?N were investigated. For 1 a , an unusual nitrile–nitrile coupling to 1‐titana‐2,5‐diazacyclopenta‐2,4‐diene ( 2 ) at ambient temperature was observed. At higher temperature, the C?C coupling of two nitriles resulted in the formation of a dinuclear complex with a four‐membered diimine bridge ( 3 ). The reaction of 1 b with Ph?C?N afforded dinuclear compound 4 and 2,4,6‐triphenyltriazine. Additionally, the reactivity of 1 b towards other nitriles was investigated. 相似文献
The synthesis of ansa complexes has been studied intensively owing to their importance as homogeneous catalysts and as precursors of metal‐containing polymers. However, paramagnetic non‐metallocene derivatives are rare and have been limited to examples with vanadium and titanium. Herein, we report an efficient procedure for the selective dilithiation of paramagnetic sandwich complex [Cr(η5‐C5H5)(η6‐C6H6)], which allows the preparation of a series of [n]chromoarenophanes (n=1, 2, 3) that feature silicon, germanium, and tin atoms at the bridging positions. The electronic and structural properties of these complexes were probed by X‐ray diffraction analysis, cyclic voltammetry, and by UV/Vis and EPR spectroscopy. The spectroscopic parameters for the strained and less strained complexes (i.e., with multiple‐atom linkers) indicate that the unpaired electron resides primarily in a d orbital on chromium(I); this result was also supported by density functional theory (DFT) calculations. We did not observe a correlation between the experimental UV/Vis and EPR data and the degree of molecular distortion in these ansa complexes. The treatment of tin‐bridged complex [Cr(η5‐C5H4)(η6‐C6H5)SntBu2] with [Pt(PEt3)3] results in the non‐regioselective insertion of the low‐valent Pt0 fragment into the Cipso? Sn bonds in both the five‐ and six‐membered rings, thereby furnishing a bimetallic complex. This observed reactivity suggests that ansa complexes of this type are promising starting materials for the synthesis of bimetallic complexes in general and also underline their potential to undergo ring‐opening processes to yield new metal‐containing polymers. 相似文献
Summary: The metallocenes rac‐C2H4(Ind)2ZrCl2 ( 1 ), rac‐Me2Si(Ind)2ZrCl2 ( 2 ), and rac‐Me2Si(2‐Me‐benz[e]Ind)2ZrCl2 ( 3 ) efficiently copolymerize propene and 5‐vinyl‐2‐norbornene (VNB). 1 and 2 give a high VNB content and high productivities, whereas 3 gives moderate incorporation. Surprisingly, precatalysts 1 and 2 , which have very closely related structures, showed very different reactivities toward VNB, with 1 having a greater affinity for VNB than for propene. The copolymers are quantitatively converted into polyolefins with polar functionalities.
The polymerization and copolymerization of vinylcyclohexane with α-olefins in the presence of several heterogeneous and homogeneous catalytic systems were studied. It was shown that, with respect to activity in the polymerization of vinylcyclohexane, the tested catalysts can be arranged in the following order: α-TiCl3 < titanium-magnesium catalyst < metallocene catalyst. Poly(vinylcyclohexane) prepared with heterogeneous catalytic systems is a solid semicrystalline polymer. The properties of polymers synthesized with homogeneous systems differ substantially depending on the type of the metallocene used. In the presence of metallocenes with a C2 symmetry, crystalline powderlike products arise, while in the case of metallocenes with C1 and Cs symmetries, polymerization yields amorphous viscous products. Molecular-mass distributions of poly(vinylcyclohexane) samples prepared using both heterogeneous titanium-magnesium catalysts and homogeneous metallocene complexes show a bimodal pattern, indicating the heterogeneity of active centers of these catalysts. Upon introduction of a comonomer (ethylene, propylene, and 1-hexene) into the reaction mixture, the activity of all studied catalytic systems increases. When Me2C(3-Me-Cp)(Flu)ZrCl2 and rac-Me2SiInd2ZrCl2 are used as catalysts, the degree of crystallinity of the copolymers grows owing to the presence of ethylene or propylene units in poly(vinylcyclohexane) chains. 相似文献