Metallocene types

Figure 2 Different metallocene types for polyethylene. (From Ref. 2.)...

A new TPV based on PP matrix in which a metallocene-type ethylene-octene (EO) copolymer is in dispersed phase has been synthesized and characterized by Fritz et al. [64]. The EO copolymers... 

Petitjean, L., Pattou, D., Ruiz-Lopez, M. F., 1999, Theoretical Study of the Mechanisms of Ethylene Polymerization with Metallocene-Type Catalysts , J. Phys. Chem. B, 103, 27. 

In all cases, the l,l -diheteroferrocenes have metallocene-type structures in which the Fe atom is sandwiched between two symmetric tj5-heterolyl rings. Although the heterolyl rings are not planar, the four C... 

Recent advances in the development of well-defined homogeneous metallocene-type catalysts have facilitated mechanistic studies of the processes involved in initiation, propagation, and chain transfer reactions occurring in olefins coordi-native polyaddition. As a result, end-functional polyolefin chains have been made available [103].For instance, Waymouth et al.have reported about the formation of hydroxy-terminated poly(methylene-l,3-cyclopentane) (PMCP-OH) via selective chain transfer to the aluminum atoms of methylaluminoxane (MAO) in the cyclopolymerization of 1,5-hexadiene catalyzed by di(pentameth-ylcyclopentadienyl) zirconium dichloride (Scheme 37). Subsequent equimolar reaction of the hydroxyl extremity with AlEt3 afforded an aluminum alkoxide macroinitiator for the coordinative ROP of sCL and consecutively a novel po-ly(MCP-b-CL) block copolymer [104]. The diblock structure of the copolymer... 

In recent years we have developed a new type of planar-chiral ligand system which is based on a phosphaferrocene skeleton equipped with an additional donor function Y [8]. This structure is closely related to the well-known ferrocene-type ligands in that a CH unit of the latter has been replaced by a P atom. The phosphaferrocene moiety serves as both a chiral metallocene-type backbone and as a donor group via the phosphorus atom lone pair. These new ligands are unique in their topological architecture and show interesting ligand properties. 

Reaction of the anion 21 with Cp or Cp metal fragments provides further metallocene-type complexes with a pendant phosphaferrocene side-chain. For example, the reaction of the thallium derivative T1 21 with [Cp RhCl2]2 yields the cationic pentamethylrhodocenium 24 as its chloride (Scheme 1.5.10). This is an interesting species because it is a chiral water-soluble P ligand. The chloride anion can be exchanged by PF,s to make the compound more soluble in organic solvents. 

Desurmont, G, Tokimitsu, T., and Yasuda, H. (2000) First controlled block copolymerizations of higher 1-olefins with polar monomers using metallocene type single component lanthanide initiators. Macromolecules, 33, 7679. 

There are two types of single site catalysts. The most well-known are based on metallocenes. Non-metallocene types are a relatively recent development and most are based upon chelated compounds of late transition metals, primarily Pd, Ni and Fe. Each single site catalyst type is addressed below. 

Within the past five years, commercial interest in metallocene catalyst components for the polymerization of olefins has increased enormously. Commercial production of a rising number of polyolefin types from different companies is creating a burgeoning and highly diversified demand for metallocenes. New brand names (e. g., Metocene (Basell), Elite (Dow Chemical), Engage (DuPont), Exact (ExxonMobil), Luflexen (Basell), Apel (Mitsui Chemicals), Borecene (Borealis), Finathene (TotalFinaElf), Topas (Ticona), just to name a few) characterize polyolefins such as PE, elastomers, PP, cycloolefin copolymers (COCs) and PS from metallocene-type catalysts [1-3]. 

Among a series of the 18-electron half-metallocene-type ruthenium complexes (Ru-4, Ru-5, and Ru-6), the indenyl derivative Ru-5 led to the fastest living radical polymerization of MMA.60 In this case, additives such as aluminum alkoxides are not necessary for controlled polymerization. However, addition of an amine such as n-Bu2NH dramatically increased the rate to complete the polymerization in 5 h at 100 °C without broadening the MWDs.61... 

Polytransoctanamer (PTO) has been used as a high performance elastomer and in blends with commodity and engineering resins. Polyoctadecene (POD) blends with PP are thermochromic. The most interesting are the metallocene-type polycyclic polyolefins, e.g., polycyclopentene or polynor-bornene, either syndiotactic or isotactic with T =400-600°C. 

Metal-based drugs have probably had most impact in the area of cancer therapy, with cisplatin still used to treat approximately 70% of all cancer patients. Cisplatin is particularly useful for treatment of testicular, ovarian, oropharyngeal, bronchogenic, cervical, and bladder carcinomas, lymphoma, osteosarcoma, melanoma, and neuroblastoma. Metallocene-type compounds were the first organometallic compounds to be evaluated in cancer therapy, and until recently, Ti(77 -C5H5)2Cl2 was undergoing clinical trials (see above). Despite this setback to the field,... 

As mentioned in the introduction, metallocene-type complexes based on the early transition metals were evaluated as anticancer compounds shortly after the discovery of cisplatin. While the biological activity of each of the metallocene dihalides is unique, titanocene dichloride 7 has been the subject of a number of studies and even entered clinical evaluation, although evaluation was discontinued (not due to its anti-proliferative properties), principally due to formulation problems, despite showing superior activity to certain cancers than other established drugs. This class of compound continues to be modified and studied for anticancer activity, for example, the titanocene-type derivative of tamoxifen 1, described above, and other developments described below. 

VLDPE Increased comonomer content giving lower density and lower Tin. ZN and metallocene type available Soft PE that can be blended with stronger PE to improve toughness, heat sealing, and elasticity... 

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