Boron-Bridged Group-4ansa-Metallocene Complexes

Abstract

Boron‐bridged group‐4 ansa‐metallocene complexes are newcomers to the field of metallocene‐mediated olefin polymerization catalysis. Because of the Lewis acidity of the boron bridge, it is more reactive than the more common carbon and silicon bridges. It is also more vulnerable to cleavage from the ligand framework by nucleophilic agents. A primary goal of our work is to involve the boron bridge more actively in the reaction chemistry of the metallocene while keeping the bridge intact.

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

“…They proposed (4,4 0 ,5,5 0 -tetramethyl)bis(fluorenylidene)(1,2-ethylidene) zirconium dichloride as the most active metallocene complex there. The reactivity and structures for metallocene bridging with boron atoms were also studied by some groups [6][7][8][9][10][11][12].…”

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

“…Since Kaminsky and co-workers [1,2] discovered metallocenes bridging with Si atom between ligands as cyclopentadienyl (Cp) for the catalysis of polymerization in 1980, ansa-metallocenes of the early transition metals have attracted attention for homogeneous catalysis. 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.…”

Piperidino Substituted [1]Borametallocenophanes. Synthesis, Reactivity, and Structure

“…Furthermore, the potential of the Lewis acidic boron centre for an intramolecular activation is envisaged [3]. It is known that Lewis acidic boron compounds can be used as cocatalysts [4], and hence, the concept of intramolecular activation arose.…”

“…1,type IV) is mediated either by π-donation from an amino group or by the formation of base adducts ( Fig. 1) [3,5].…”

“…Rufanov et al described the only example of a base free three-coordinated boron-bridged complex [8]. However, the complex was poorly characterized and the validity of this assignment was challenged by other authors [3].…”