Although DFT geometries are typically in very good agreement with experiment for transition metal complexes, the Cr-Cr multiple bond presents particularly challenging electronic structure that leads to stark differences between DFT geometries and diffraction measurements. For these three complexes, the Cr-Cr distances obtained by DFT deviate from diffraction by 0.151 to 0.641 Å for the ground state singlet (Table ). DFT severely underestimates the Cr-Cr bond distance, because the electronic state is not described properly and is not a result of functional choice. The Cr-Cr distance in the M06 triplet geometry ranges from 1.922 to 2.497 Å for the three complexes (Table ) Although Cr-ligand bond distances are in good agreement with experiment (Table ), the difference between the computed and measured Cr-Cr bond distances are larger than what can be considered excellent agreement despite the clear improvement over DFT. Ruipérez et al. studied diatomic Cr 2 and showed that larger IPEA shifts resulted in shorter Cr-Cr distances. The effect of the choice of zeroth-order Hamiltonian in these complexes is presented vida infra.