Structural Characterization of Electron Donors in Ziegler–Natta Catalysts

Abstract

Ziegler–Natta catalysis is a very important industrial process for the production of polyolefins. However, the catalysts are not well-understood at the molecular level. Yet, atomic-scale structural information is of pivotal importance for rational catalyst development. We applied a solid-state NMR/density functional theory tandem approach to gain detailed insight into the interactions between the catalysts’ support, MgCl2, and organic electron donors. Because of the heterogeneity of the samples, large line widths are observed in the carbon spectra. Despite this, good agreement between experimental and computational values was reached, and this shows that 1,3-diether based donors coordinate at (110) surface sites, while phthalates are less selective and coordinate at both (104) and (110) surface sites.

Probing Interactions between Electron Donors and the Support in MgCl2-Supported Ziegler–Natta Catalysts

“…Ball milling MgCl 2 in the presence of electron donors yields nanoparticles with much smaller dimensions. On the basis of previous results, 34 we printed the most likely surface type for each sample in bold.…”

“…Furthermore, we calculated quadrupolar parameters for MgCl 2 (110)–TiCl 4 , MgCl 2 (104)–DMDOMe, and MgCl 2 (110)–DMDOMe adducts using periodic calculations. We used cluster models that were introduced in ref ( 34 ), for the calculations of the quadrupolar parameters for DiBP adducts and for a high-coverage model of DMDOMe. In the calculations, the donor molecules are coordinated in either the “bridge” or the “chelate” mode (see Figures 5 , S8, and S9 ) and TiCl 4 adopts the so-called Corradini site (see Figure 6 ).…”

“…In ref ( 56 ), an alternative cluster description has been presented that should be better suited to describe such disordered systems. On the basis of this cluster approach, we proposed some high-coverage models 34 that were indeed found to better describe the MgCl 2 –DMDOMe adducts as far as 13 C chemical shifts of the donor are concerned. Quadrupole parameters have been calculated for the optimized cluster model with three donors on the surface that has been shown in ref ( 34 ) and is reproduced in Figure S6 .…”

“…Optimized cluster models for the DiBP donor in different conformation on both (104)- and (110)-surfaces were presented in ref ( 34 ) as well. The structures of these models are reproduced in Supporting Information Figure S7 .…”

Bis-(salicylaldehyde-benzhydrylimino)nickel complexes with different electron groups: crystal structure and their catalytic properties toward (co)polymerization of norbornene and 1-hexene

“…In order to achieve this goal, it is important to synthesize some efficient catalysts. It is wellknown that conventional Ziegler-Natta catalysts 26,27 and metallocene catalysts [28][29][30] have many disadvantages due to their polar centers as early transition metals, for instance, poor tolerance to polar groups and large amounts of cocatalyst. However, owing to the lower oxophilicity, single active site and resistance toward deactivation by polar functionalities, the design of late-transition-metal catalysts has attracted widespread interest.…”