Emphasis is placed on first row TM complexes with d electron configurations ranging from d 4 to d 8 that adopt different spin states depending on the nature of the metal and its coordination environment. Note that second and third row TM complexes are less cumbersome, as they typically exhibit low spin configurations due to larger crystal field splitting. As a starting point, we took the database containing 31k transition metal complexes we extracted from the CSD using cell2mol. This database 22 excludes polynuclear complexes, for which the total spin assignment would depend upon the coupling between spin-bearing metal centers, and complexes with formally radical ligands. This results in 17,214 mononuclear first row complexes with five metal centers: Cr, Mn, Fe, Co, and Ni. Among these complexes, we excluded those with haptic ligands (e.g., cyclopentadienyl) because their coordination numbers and geometries are ambiguous. We also eliminated complexes with nitrosyl ligands to avoid potential spin from typical noninnocent ligands. The coordination geometry of the TM complex was then determined using the CoSymLib python library and complexes exhibiting significant deviation from the ideal shape of a reference polyhedron were removed.