How To Give A Name To A Coordination Complex SpeciesIt is a tricky job to name a coordinationcomplex because a such type of complex is consist of many parts i.e. a centralmetal ion, counter ions, ligands, where ions (may be +ve or -ve) mainly fulfillthe primary valencies, which in turn counterbalance the charge of thecoordination sphere (Central atom + ligands) and ligands mainly satisfy thesecondary valency. Ligands can be neutral, positively charged (cationic ligand)or negatively charged (anionic ligand). So, there are some rules approved byIUPAC (International Union of Pure and Applied Chemistry)to name the central ion, ligands and ions to get an appropriate nomenclature ofthe coordination complex. Here we will basically learn the rules and how toapply them for such nomenclature.
Before going to the rules we can take alook to the different part of a coordination compound.Now come to the rules.Rule 1: The naming should start withligands maintaining alphabetic order if there are more than one type of ligandsand after that central metal ion should be named.
Rule 2: i. For anionicligands, the name should end with “o”. For anions ending with “ide” (chloride,bromide etc.), ”ate” (nitrate, sulphate etc.) and “ite” (nitrite, sulphiteetc.
), the changes will be “ido” (Chlorido, bromido etc.), “ato” (nitrato,sulphato etc.) and “ito” (nitrito, sulphito) respectively.ii. For neutralligands, common name of the molecules should be used. (Some exceptions arethere: water is named as aqua, ammonia is named as ammine, CO is named ascarbonyl and N2 and O2 are named as dinitrogen anddioxygen respectively.)Rule 3: When more than one ligands areconnected to the central metal ion then di, tri, tetra, penta etc. prefixes areattached with the ligand name.
When the ligand name contains already theseprefixes then bis, tris, tetrakis, pentakis etc. are used instead of di, tri,tetra, penta respectively.Rule 4: Cation name should be written first and thenanion name should be written for an ionic coordination complex.Rule 5: Oxidation number should be writtenin roman digit with sign in a first bracket () after the central metal ionname.Rule 6: For cationic or neutral complex,the usual name of the central metal ion should be used. But in case of anioniccomplex, the “ate” suffix is attached with the usual metal name. (e.
g. copperis changed cuprate, molybdenum is changed to molybdate etc.)Rule 7: In case of ambidentate ligand (onehaving two donor site), the naming of the ligand depends upon which donor siteis binding to the central metal ion, e.g. SCN- (donor atom S) iscalled as thiocyanato or S-thiocyanato and NCS- (donor atom N) is called asisothiocyanato or N-thiocyanato etc. In GAMSAT following type of question canbe asked with suitable vignette. Have a look.