The Role of Bridging Group of Cyclopentadienyl Ligands for the Ziegler–Natta Catalysis: Theoretical Study

Abstract

The potential energy surfaces of the initial reactions of ethylene insertion for the Ziegler-Natta catalysis with bridging groups of Cp ligands were studied by ab initio MO and density functional methods. Three metals (Ti, Zr, and Hf) in the Zeigler-Natta catalysis and eight bridging groups (BH, CH 2 , NH, O, AlH, SiH 2 , PH, and S) were treated. For the complex formation between ethylene and metallocenes, two type structures (vertical and horizon) were found. The vertical type structures are more stable in energy than the horizon types. The formation energy of the complex between ethylene and the metallocenes by incorporation of bridging atom or group is related to the geometrical hindrance and the bond interaction as shown in the case of boron bridging system.

Theoretical studies on the role of bridging group of CGC type ligands for the Ziegler–Natta catalysis

“…The complex formation energies for each metal system correlate to the tilt angles for the bridging systems of the first-and the second-row atoms, except for the BH-bridging systems. The linearity of the relation is much poor than that of ansa-metallocenes in the previous paper [15]. The relation between the activation energies and the tilt angles is also shown in Fig.…”

“…Recently, the reactivity and the structures of ansa-metallocenes with several bridging atoms or groups were studied experimentally [3][4][5][6][7][8][9][10][11][12][13][14]. In our previous paper [15], the structures and the energies of the initial reaction of ethylene polymerization for the Ziegler-Natta catalysis with eight bridging groups of Cp ligands were studied by an ab initio MO and a density functional method. We pointed out two effects of the bridging groups for the energy of the reaction: one is the geometrical hindrance as the tilt angle and the other is the bond interaction.…”