Background and overview[1]
Aromatic hydrocarbon-transition metal sandwich complex (i) is a complex containing a transition metal central atom and π of two aromatic ligands surrounding the transition metal central atom in a sandwich-like structure The electronic system is coordinated, that is, the transition metal central atom is located between the faces of two parallel aromatic ligands. The two ligands of the sandwich complex may be the same (sandwich homo complex) or different (sandwich hetero complex). The aromatic ligand is selected from the group consisting of benzene-type aromatic ligands (eg benzene) and non-benzene-type aromatic ligands (eg cyclopentadienyl).
An exemplary arene-transition metal sandwich complex in which two aromatic ligands are of the benzene type is diphenylchromium, in which the chromium central atom is located between two benzene ligands in a sandwich-like structure. Other aromatic hydrocarbon-transition metal sandwich complexes in which the two aromatic ligands are of the benzene type are known to those skilled in the art. An exemplary arene-transition metal sandwich complex in which the two aromatic ligands are non-benzene is a metallocene. Metallocenes are bis(eta5-cyclopentadienyl) complexes of transition metals.
In the complex, the transition metal central atom is located between two cyclopentadienyl ligands in a sandwich structure. The transition metal is preferably selected from the group consisting of iron, nickel, cobalt and osmium and chromium. DIBENZENECHROMIUM, with the molecular formula C12H12Cr, is used as a polymerization catalyst.
Preparation[1]
The preparation of diphenylchromium is as follows: in the presence of benzene, aluminum trichloride is used as a catalyst, and chromium trichloride is reduced with metallic aluminum to generate diphenylchromium tetrachloroaluminate [Cr(η6-C6H6)2]·[ AlCl4], which is then reduced to neutral diphenylchromium using an aqueous dithionite solution.
Main reference materials
[1] CN201680071977.X Method for preparing salts of aromatic hydrocarbon-transition metal sandwich complexes
