Quintuple bonding in a dimetal complex

In principle, a homodinuclear transition-metal species can form up to six bonds using the ns and five (n-l)d valence orbitals. In a simplified bonding description of Ar CrCrAr, the planar C-Cr-Cr-C skeleton has idealized molecular symmetry C2h with reference to a conventional z axis lying perpendicular to it. For each chromium atom, a local z axis is chosen to be directed toward 

Molecular geometry and structural formula of the dinuclear complex Ar CrCrAr (Ar = C6H3-2,6(C6H3-2,6-iPr2)2. 

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