The critical importance of accounting for the static electron correlation associated with the RAS1/RAS3 orbital spaces manifests in the predicted spin-state energy ladders, shown for the 𝑋 110-I geometry in Figure . The PT2 and PDFT calculations that are based on the CAS(8e,8o) reference, i.e., which omit orbitals including the chromium dzx and dyz combinations, disagree qualitatively with those based on the RAS(16e,16o) reference. The CAS(8e,8o)-based calculations predict a quintet ground state with the triplet being 3000 cm -1 or more higher in energy, depending on the dynamical correlation method. The RAS(16e,16o)-based calculations, by contrast, predict a triplet ground state, with the quintet state being 600 cm -1 or more higher in energy, depending on the dynamical correlation method. (Interestingly, the RASSCF(16e,16o) spin-state energies themselves agree qualitatively with those computed at the CASSCF(8e,8o) level, suggesting that there is a complicated interplay of static and dynamical correlation effects influencing the spin-state energy ladder.) Considering all geometries at all temperatures, RASPT2 and RAS-tPBE agree on the energy ordering of the three spin states in every case (see Table in the SI).