The correlation of the calculated total Fe-S/L covalency (%L) with VDE (open square) and VRE (open triangle) of [Fe4S4L4]2− (left to right, L=Cl, SH, S-t-butyl, SCH3, SeCH3, H, PH2, and P(CH3)2 and with VDE (solid square) and VRE (solid triangle) of [Fe4S4(SEt)4]2− for the spin-delocalized state (SDL), the spin-localized state (SL), with waters hydrogen bonded to the bridging (HBb) and terminal (HBt) sulfurs, and in the Fd- and HiPIP-like conformations.