Setting valence constraints for the atoms involved in simple organic molecules is fairly straightforward; carbon and nitrogen should not have more than four bound neighbors, hydrogen and fluorine can only have one bound neighbor and so on. Defining valence constraints for transition metals is a lot more complicated. Initially, the AC of the complex is found based on atom pair distances as described above. The valence constraints are invoked based on the non-TM atoms, cutting the longest bond relative to the atomic radii of the atoms involved in the bond if a ligand atom has too many neighbors. In some cases, this leads to a "fake" haptic bonding pattern i.e. a situation where the neighbor-atom of a coordinating atom is initially also assigned a bond to the transition metal even though the distance to the TM is significantly larger (Figure ). We avoid this by cutting perceived haptic bonds that are much longer than those for their haptic neighbors.