The d orbitals directed along the Re–Cl bonds are stabilized by interaction with chlorine ligand orbitals and do not contribute to Re–Re bonding. In contrast, the [Os2Cl8]2− ion with two more electrons (σ2π4δ2δ*2) has an Os–Os triple bond and a staggered geometry.
The d orbitals on rhodium (Rh) atoms in the Re-Cl bonds are stabilized by interaction with chlorine ligand orbitals, but do not contribute to Rh-Rh bonding. In contrast, the [Os2Cl8]2− ion has two more electrons (σ2π4δ2δ*2), resulting in an Os-Os triple bond and a staggered geometry.