Arene complexes
Aromatic compounds are 6-electron donors that coordinate to transition metals in the η6 coordination mode with six carbon atoms. Bisbenzenechromium, Cr(C6H6)2, is a typical example of such a compound. The compound is prepared by reducing chromium chloride in benzene and it has a sandwich structure in which a chromium atom is inserted between two benzene rings. When a benzene ligand is replaced by three carbonyls,Cr (CO)3(C6H6) is obtained.