Cut metal bonds to isolate the ligands Babel , a bond (one in the AC) is created if the distance between two atoms is shorter than the sum of their covalent radii plus a tolerance of 0.45 Å. Since this can create valence violations (e.g. five bonds to carbon), a subsequent filter is applied cutting the weakest bond to an atom until the valence requirements are met. Here, the weakest bond is defined as the longest bond relative to the covalent radii of the atoms. More exotic bonding environments such as bridging hydrogen atoms can thus not be described using the default settings since this would violate the maximum valence of hydrogen which is one.