Chapter 22.4, Problem 22.1E

Interpretation Introduction

Interpretation:

IUPAC name for the following compounds has to be written.

(a)   $\left[Co{(N{H}_3)}_{5}Cl\right]C{l}_2$    (b)  $K_2\left[Co(H_{2}O){(CN)}_5\right]$   (c) ${\left[Fe{(H_{2}O)}_5(OH)\right]}^{2+}$

Concept Introduction:

Complex compounds are primarily formed by transition elements which are d-block elements.  A co-ordination compound is known as a complex compound is made of metal atom/ion and ligand(s).  Ligands are considered as Lewis bases and the central metal atom is Lewis acid.  Ligands donate a pair of electron to metal ion and establish bonding with metal ion which is known as co-ordinate bond and hence these compounds are named as co-ordination compounds.  The ligands represented inside the square brackets adjacent to the central metal ion, which is termed as co-ordination sphere.

IUPAC has devised rules to name a co-ordination compound in chemical terminology.  The rules are stated below -

• Name of the cation must be written before the name of the anion.
• Metal ions are named first followed by ligand names.
• If the ligand is negatively charged, the name of the ligand carries suffix 'o'.  example - $CN$ is a negative ligand and it must be named as 'cyano' not cyanide.
• Number of simple ligands present in a co-ordination compound is denoted by prefixes - mono-, di-, tetra-, etc., so on.
• The prefixes bis-, tris-, tetrakis,- etc are used to denote the number of complicated ligands.
• Oxidation state of the central metal ion must be mentioned using a Roman numeral in parentheses.
• The ligands are named in alphabetical order if a complex contains more than one ligand.
• The suffix 'ate' is added to the name of the central metal atom in case of negatively charged complex ion.  While naming some of the metals, their Latin name is preferred.