Coordination Compounds: Terms, Nomenclature and Isomerism — Part 2: Naming and isomerism: visual lesson, ISC Class 12 Chemistry

Lesson

Names and shapes

Part 2 — how to name complexes by IUPAC rules and how the same formula can give different compounds.

In this lesson you will

Write IUPAC names of mononuclear coordination compounds and formulae from names
Identify ionisation, linkage, coordination and hydrate isomers
Draw geometrical (cis/trans, fac/mer) and optical isomers of simple octahedral and square planar complexes

Concept

IUPAC rules for naming

(1) Cation first, then anion, as in simple salts. (2) Within the complex: ligands first, in alphabetical order, then the metal. (3) Prefixes di-, tri-, tetra- for simple ligands; bis-, tris-, tetrakis- (with brackets) for ligands whose names contain numbers or prefixes. (4) Metal oxidation state in Roman numerals in brackets. (5) An anionic complex ends in -ate, with Latin roots for some metals. (6) Neutral complexes are one word.

Table of metal names used in anionic complexes
Metal	In an anionic complex
Iron	ferrate
Copper	cuprate
Silver	argentate
Gold	aurate
Lead	plumbate
Tin	stannate
Zinc, aluminium, cobalt	zincate, aluminate, cobaltate

Concept

Names of ligands

Anionic ligands end in -o (chlorido, cyanido, hydroxido, oxalato, sulfato). Neutral ligands keep their names except aqua (H₂O), ammine (NH₃), carbonyl (CO) and nitrosyl (NO). For ambidentate ligands, the donor atom is shown: nitrito-N, nitrito-O, thiocyanato-S, thiocyanato-N.

Table of IUPAC ligand names
Ligand	Name	Ligand	Name
F⁻	fluorido	H₂O	aqua
Br⁻	bromido	NH₃	ammine
OH⁻	hydroxido	CO	carbonyl
CN⁻	cyanido	NO	nitrosyl
C₂O₄²⁻	oxalato	en	ethane-1,2-diamine
NO₂⁻ (N)	nitrito-N	SCN⁻ (S)	thiocyanato-S

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