Chapter 22, Problem 61AP

Interpretation Introduction

Interpretation:

The oxidation number and number of unpaired electrons in the given coordination compounds are to be determined.

Concept introduction:

The oxidation number ofa metal atom is equal to the charge on the metal atom.

In low spin, the crystal filed splitting is large. So, the lower orbitals are filled completely before the upper orbitals are populated.

Ligands that cause a high degree of splitting among the $d$-orbital energy levels produce strong magnetic fields and low spin complexes. Weak-field ligands, on the other hand, cause small degree of splitting among the $d$-orbital energy levels and result in high spin complexes.

The weak-field ligand makes valence electrons enter into separate $d$-orbitals ($d_{xy},d_{yz}\text{, }{d}_{zx}\text{ and }{d}_{x^2-y^2},d_{z^2}$) but strong-field ligands make them enter into lower-energy $d$-orbitals ($d_{xy},d_{yz}\text{and }{d}_{zx}$).

Spectrochemical series: ${\text{I}}^{-}{\text{< Br}}^{-}{\text{< Cl}}^{-}{\text{< OH}}^{-}{\text{< F}}^{-}{\text{< H}}_2{\text{O < NH}}_3{\text{< en < CN}}^{-}\text{< CO}$

These ligands are arranged in order of increasing value of $\Delta$.

${\text{CN}}^{-}$ and $\text{CO}$ are strong field ligands because they cause large splitting of the d-orbital.

Strong field ligands form low spin complex.

The halide and hydroxide ion are weak field ligands because they cause less splitting of the d-orbital

Weak field ligands form high spin complex.