Cr(III) Complexes Bearing a β-Ketoimine Ligand for Olefin Polymerization: Are There Differences between Coordinative and Covalent Bonding?

Zirconium enolatoimine complexes in olefin polymerization.

Zirconium complexes with enolatoimine ligands bearing an electron-withdrawing trifluoromethyl group on the alkoxy moiety [κ²-N,O-{2,6-R₂N=C(CH₃)C(H)=C(O)CF₃]₂ZrCl₂ (2a, R = H; 2b, R = F; 2c, R = CH₃; 2d, R = (i)Pr) were prepared. The isopropyl substituents hinder rotation in solution for 2d, and result in a trans-arrangement of the N-donors in the solid state. Catalyst activities are similar fo...

Metal–ligand bonding in metallocenes: Differentiation between spin state, electrostatic and covalent bonding

We have analyzed metal–ligand bonding in metallocenes using density functional theory (DFT) at the OPBE/TZP level. This level of theory was recently shown to be the only DFT method able to correctly predict the spin ground state of iron complexes, and similar accuracy for spin ground states is found here. We considered metallocenes along the first-row transition metals (Sc–Zn) extended with alk...

Method for Prevention of Solid Dissolution Through Covalent Ligand Bonding

Are There Any Differences in Seismic Performance Evaluation Criteria for Concrete Arch Dams?

Differences between stress-based and strain-based criteria are investigated in seismic performance evaluation of the arch dams in time domain. A numerical model of the coupled dam-reservoir-foundation system is prepared with the finite element technique. Reservoir is modeled using the Eulerian approach as a compressible domain, and the foundation rock is assumed to be massless. Dynamic equilibr...

Zirconium complexes bearing a tetradentate dipyrrolyl ligand.

Using a tetradentate, dianionic ligand several new zirconium complexes have been prepared. These pyrrolyl compounds, unlike their titanium analogues, are inactive in hydrohydrazination catalysis. However, they are quite stable, and their reactivity with H2NR, where R = Ph, C6H11, and NHPh, is reported here. Two of the complexes were characterized by X-ray diffraction.