Rajasthan BoardEnglish MediumSTD 12 ScienceChemistryCoordination Compounds3 Marks
Question
Write down rules for $\text{IUPAC}$ naming of Co ordination entities.
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Answer
$\rightarrow$ The following rules are used when naming coordination compounds:
$(i)$ The cation is named first in both positively and negatively charged coordination entities.
$(ii)$ The ligands are named in an alphabetical order before the name of the central atom / ion.
$(i) $ Names of the anionic ligands end in $-o,$ whereas those of neutral and cationic ligands are the same except aqua for $\ce{H_2O},$ ammine for $\ce{NH_3},$ carbonyl for $\ce{CO}$ and nitrosyl for $\ce{NO}$.
While writing the formula of coordination entity, these are encloded in brackets .
$(iv)$ Prefixes mono, di, tri, etc., are used to indicate the number of the individual ligands in the coordination entity. When the names of the ligands include a numerical prefix, then the terms, bis, tris, tetrakis are used, the ligand to which they refer being placed in parentheses.
For example $,\ce{ [NiCl_2(PPh_3)_2]}$ is named as dichloridobis $($triphenylphosphine$)$ nickel $(II).$
$(v)$ Oxidation state of the metal in cation, anion or neutral coordination entity is indicated by roman numeral in parenthesis.
$(vi)$ If the complex ion is a cation, then the metal is named same as the element.
For example, $Co$ in a complex cation is called cobalt and $Pt$ is called platinum. If the complex ion is an anion, the name of the metal ends with the suffix $-$ ate.
For example $, Co$ in a complex anion $,\ce{ [Co(SCN)_4]^{2-}}$ is called cobaltate.
For some metals, the Latin names are used in the complex anions. e.g. ferrate for $Fe$.
$(vii)$ The neutral complex molecule is named similar to that of the complex cation.
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