FI catalysts

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. 

Because an FI catalyst has a pair of non-symmetric phenoxy-imine ligands, it potentially possesses five isomers stemming from the coordination modes of ligands. Zr-, Ti-, and Hf-FI catalysts 1-3 display three sets of signals in XH NMR, attributed to the imine proton, suggesting that these FI catalysts exist as isomeric mixtures in solution, which is probably an intrinsic feature of FI catalysts. On the basis of the symmetry of the possible isomers A-E (Fig. 10), as well as the relative formation... 

X-ray crystallographic analyses demonstrate that, in the solid state, Zr- and Ti-FI catalysts 1 and 2 possess approximately octahedrally coordinated metal centers and C2 symmetry, with a trans-O, cis-N, and cis-C 1 disposition (isomer A) (Fig. 11). 

These results indicate that FI catalysts favor the isomer A structure, and that they can be present as a mixture of isomers A and B in solution. It is important to note that an FI catalyst generally exhibits fluxional character in solution, which can result in unique polymerization catalysis. 

Fig. 12 Calculated structure of an ethylene-coordinated cationic methyl species derived from FI catalyst 1...

Fig. 13 DFT calculation results for ethylene polymerization with FI catalyst 1/MAO...

Conversely, Ti-FI catalysts with MAO normally show lower (but still high) ethylene polymerization activities and form higher molecular weight PEs relative to the Zr congeners. The ethylene polymerization activities of Ti-FI catalysts were also... 

Table 2 Ethylene polymerization with fluorinated Ti-FI catalysts...

Ethylene Polymerization Behavior of FI Catalysts with Cocatalysts Other than MAO... 

The ethylene polymerization behavior of FI catalysts has been described in previous sections. It is often observed that the cocatalyst that is employed has an influence on the catalytic behavior of a transition metal-based olefin polymerization catalyst. FI catalysts can exhibit unique catalytic behavior depending on the cocatalyst that is used for polymerization. 

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