1 Cyclic compounds 1.1 If the chelating atom was within a cycle, the entire cycle was defined as the initial metal-chelating group. 1.2 If the atom was not part of a cycle, the shortest path to a cycle was identified. If the path was ≤ 2 bonds, the path and the cycle itself would comprise the initial chelating group. If the path was > 2 bonds, the ligand was processed as an aliphatic compound as described below. 1.3 In case there was one aliphatic heteroatom within 2 bonds distance of the chelating atom, the chemical environment of the initial chelating group was expanded to include the path to this atom. 2 Aliphatic compounds 2.1 If there was a heteroatom within 2 or 3 bonds from the chelating atom, the path to this atom comprised a chelating group. If no heteroatom was found, the chelating atom and the carbon atom bound to it were defined as the chelating group. Two chelating groups could be extracted, one from the path with 2 bonds and another from the one with 3. B Polydentate ligands (≥ 2 chelating atoms within 2.6 Å from the metal ion) 1