The aromatic P5 ring generates a strong ligand field which plays a decisive role in determining the total spin of the ground electronic state of the molecule. At all temperatures, four of the eight formally unpaired d electrons of the Cr(II) ions are involved in pπ-dπ bonds with the P5 ring. In the spin-crossover temperature range (12 K < T < 150 K), our multireference calculations show two different spin-crossover behaviors for the two dimeric units observed in XRD experiments by Goeta, A. et al. For the unit labeled "cation I," our calculations show a two-step crossover from quintet to triplet and then to singlet corresponding to the graduallydecreasing Cr-Cr internuclear distance; for the unit labeled "cation II", our calculations show an abrupt single-step crossover at T < 25 K from quintet to singlet. These results provide a detailed understanding of Goeta et al.'s analysis 26 of the observed magnetic susceptibility (Figure ).