Olefin polymerization, catalysts for

The class of catalysts we currently call Ziegler-Natta was first used by Ziegler in 

1953 to polymerize ethylene at low pressure, and further developed by Natta in 

1954 to produce isotactic polypropylene. Both Ziegler and Natta were awarded the Nobel Prize in chemistry in 1963 since then, this field has grown incessantly, with the development of improved catalysts and new industrial processes. 

Many other catalysts capable of polymerizing olefins have become available since the original Ziegler-Natta catalyst based on crystalline titanium chloride was introduced. More recently, the discovery of soluble metallocene/aluminoxane catalysts opened the doors to a new revolution in the production of polyolefins. These catalyst systems are able to make polyolefins in very high yields and with a degree of microstructural control not possible to achieve using conventional Ziegler-Natta catalysts. 

Most industrial processes today still use heterogeneous Ziegler-Natta catalysts, although the market share of metallocene resins is increasing due to the enhanced 

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Other applications of zirconium tetrafluoride are in molten salt reactor experiments as a catalyst for the fluorination of chloroacetone to chlorofluoroacetone (17,18) as a catalyst for olefin polymerization (19) as a catalyst for the conversion of a mixture of formaldehyde, acetaldehyde, and ammonia (in the ratio of 1 1 3 3) to pyridine (20) as an inhibitor for the combustion of NH CIO (21) in rechargeable electrochemical cells (22) and in dental applications (23) (see Dentalmaterials). 

Titanium bromide [7789-68-6] TiBr, is claimed as a catalyst for olefin polymerizations (18). Chromous bromide [10049-25-9] CrBr2, is used in chromizing. Chromic bromide [10031-25-1], CrBr, and tungsten bromide [13701 -86-5], are catalysts for polymerizing olefins (19). Manganese... 

These siUca-supported catalysts demonstrate the close connections between catalysis in solutions and catalysis on surfaces, but they are not industrial catalysts. However, siUca is used as a support for chromium complexes, formed either from chromocene or chromium salts, that are industrial catalysts for polymerization of a-olefins (64,65). Supported chromium complex catalysts are used on an enormous scale in the manufacture of linear polyethylene in the Unipol and Phillips processes (see Olefin polymers). The exact stmctures of the surface species are still not known, but it is evident that there is a close analogy linking soluble and supported metal complex catalysts for olefin polymerization. 

Allison, M. and Bennet, A., Novel, Highly Active Iron and Cobalt Catalysts for Olefin Polymerization, CHEMTECH, July, 1999, pp. 24-28. 

Enikolopyan NS, Diachkovsky FS, Novokshonova LA (1982) In Complex organ-ometallic catalysts for olefin polymerization Publication IKRF 9 174... 

Semikolenova NV, Zakharov VA (1982) Complex organometallic catalysts for olefin polymerization, IKhF AN SSSR Publication 9 51... 

The propagation centers of the catalysts of olefin polymerization contain the active transition metal-carbon olefin polymerization may be divided into two vast classes according to the method of formation of the propagation center two-component and one-component.1... 

In essence the active centers for catalytic polymerization of olefins are organometallic complexes of transition metals. For this reason a search for individual organometallic compounds that would possess catalytic activity in olefin polymerization is of great interest. The first attempts to use organometallic compounds of transition metals as catalysts for olefin polymerization were made long ago [e.g. CH3TiCl3 as a catalyst for polymerization of ethylene 116). However, only in recent years as a result of the application of relatively stable organometallic compounds of transition... 

Kaminsky W, Sinn H (eds) (1988) Transition metals and organometallics as catalysts for olefin polymerization. Springer, Berlin Heidelberg New York... 

Ni catalysts for olefin polymerization incorporating a-iminocarboxamide ligands are activated by the formation of borane-carbonyl adducts (153).542 Structure/reactivity relationships are similar to Brookhart s dimine catalysts. 

A dozen years later, another breakthrough was reported the use of Zr(IV)-boratabenzene complexes as catalysts for olefin polymerization (Scheme 24).40... 

Several combinatorial approaches to the discovery of transition metal based catalysts for olefin polymerization have been described. In one study Brookhart-type polymer-bound Ni- and Pd-(l,2-diimine) complexes were prepared and used in ethylene polymerization (Scheme 3).60,61 A resin-bound diketone was condensed with 48 commercially available aminoarenes having different steric properties. The library was then split into 48 nickel and 48 palladium complexes by reaction with [NiBr2(dme)] and [PdClMe(COD)], respectively, all 96 pre-catalysts being spatially addressable. 

Moreover, the molecular catalysts have provided systematic opportunities to study the mechanisms of the initiation, propagation, and termination steps of coordination polymerization and the mechanisms of stereospecific polymerization. This has significantly contributed to advances in the rational design of catalysts for the controlled (co)polymerization of olefinic monomers. Altogether, the development of high performance molecular catalysts has made a dramatic impact on polymer synthesis and catalysis chemistry. There is thus great interest in the development of new molecular catalysts for olefin polymerization with a view to achieving unique catalysis and distinctive polymer synthesis. 

In this contribution, we describe the discovery and application of phenoxy-imine ligated early transition metal complexes (FI catalysts) for olefin polymerization, including the concept behind our catalyst design, the discovery and the polymerization behavior of FI catalysts, and their applications to new polyolefinic materials. 

Fig. 5 Schematic structure of a molecular catalyst for olefin polymerization...

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