Chapter 20, Problem 20.76SP

Interpretation Introduction

Interpretation:

The structure of the iron oxalate complex ${\left[Fe{\left(C_2{O}_4\right)}_3\right]}^{3-}$ has to be drawn. Its coordination geometry should be described and if the chelate ring present, it should be identified along with determining coordination number of the compound and oxidation number of the iron in the compound.

Concept introduction:

Coordination compounds are a special class of compounds in which the metal atoms or ions are bounded to a number of anions or neutral molecules.

A coordination compound can be simply represented as follows,

Coordination number of a complex is defined as the number of ligand donor atoms to which the metal is directly bonded.

The geometry of a transition metal complex depends on the coordination number and nature of the metal ion.

Coordination number of complexes, shape with example are listed below,

$\begin{array}{ccc}\text{Coordination}\text{number}& \text{Shape}& \text{Examples}\\ \text{2}& \text{Linear}& {\left[{\text{CuCl}}_{\text{2}}\right]}^{\text{-}}\text{,}{\left[\text{Ag}{\left({\text{NH}}_{\text{3}}\right)}_{\text{2}}\right]}^{\text{+}}\text{,}{\left[{\text{AuCl}}_{\text{2}}\right]}^{\text{-}}\\ \text{4}& \text{Square}\text{planar}& {\left[\text{Ni}{\left(\text{CN}\right)}_{\text{4}}\right]}^{2-}\text{,}{\left[{\text{PdCl}}_{\text{4}}\right]}^{\text{2-}}\\ \text{4}& \text{Tetrahedral}& {\left[Zn{\left(OH\right)}_{\text{4}}\right]}^{2-}\text{,}{\left[{\text{CdCl}}_{\text{4}}\right]}^{\text{2-}}\\ \text{6}& \text{Octahedral}& {\left[\text{Ti}{\left({\text{H}}_{\text{2}}\text{O}\right)}_{\text{6}}\right]}^{\text{3+}}\text{,}{\left[\text{Co}{\left(\text{en}\right)}_{\text{3}}\right]}^{\text{3+}}\end{array}$

Chelate is coordination compound consisting of a central metal atom attached to large molecule called chelating ligand; it has a cycle or ring structure.