Stereospecific metallocene catalysts: Scope and limits of rational catalyst design

Abstract

Structure‐performance relationships in the propene polymerization behaviour of a number of silicon bridged bisindenyl zirconocenes show a rational pattern. Prognosis of the polymerization behaviour of different type structures, however, often fails, which is demonstrated by three examples of new zirconocenes. These include two bisindenyl complexes with two‐membered silicon bridges and one isospecific bridged fluorenyl cyclopentadienyl species. It is thus demonstrated that the scope of a “rational catalyst design” in the field of metallocene catalysts is still limited.

Quantification of active sites in single-site group 4 metal olefin polymerization catalysis

“…As reported in a number of review articles [for a selection, see: 1-10], a considerable diversity of group 4 metal catalyst structures has been designed and synthesized in the past decades. Ubiquitous examples involve the simplest metallocene complexes Cp2TiCl2 [11,12] and Cp2ZrCl2 [11,13] to the most elaborated ones, such as those derived from {EBI}- [14], {SBI}- [15,16], {Cp/Flu}- [17][18][19][20], half-sandwich {CGC}based [21][22][23][24] platforms and more recent post-metallocene systems such as bisphenolate [25,26], Mitsui's phenoxy-imine [27][28][29] and Dow's pyridyl-amido [30,31] Most of the studies conducted on these single-site catalysts usually focused on their productivities and on the properties of the resulting polymers. While these parameters are certainly important to assess industrial relevance, they are not enough to fully apprehend the potential of a catalyst.…”

The discovery of metallocene catalysts and their present state of the art

“…38 They were able to obtain isotactic polypropylene with an activity of 900,000 kg PP/mol Zr ⅐h, a molecular weight of 700,000 g/mol, an isotacticity of 99%, and a melting point of 160°C.…”

Copolymerization of ethylene and ?-olefins with combined metallocene catalysts. III. Production of polyolefins with controlled microstructures

“…Therefore, it is possible to control polymer microstructure by catalyst design, although the correlation between catalyst structure and chain properties still needs to be better understood. 9,10 It is also possible to control polymer microstructure (particularly if polymers with nonuniform properties are required) by the mixing of two or more single-site catalysts with known polymerization behaviors. There is no evidence of significant interaction between two metallocenes that are used simultaneously during polymerization.…”