Chapter 20, Problem 20.120CHP

(a)

Interpretation Introduction

Interpretation:

The crystal field energy-level diagrams for square planar and a tetrahedral nickel $\left(II\right)$ complex should be drawn and their population of the orbitals should be shown.

Concept Introduction:

Coordination compounds: The compounds having coordination covalent bonds which form when metal ions react with polar molecules or anions.

$Spectrochemical$ Series: The list of ligands arranged in an ascending order of $\text{(Δ)}$(the splitting of d-orbitals in presence of various ligands).

$\begin{array}{l}\stackrel{{}^{{\text{I}}^{\text{-}}\text{<}{\text{Br}}^{\text{-}}\text{<}{\text{SCN}}^{\text{-}}\text{<}{\text{Cl}}^{\text{-}}\text{<}{\text{S}}^{\text{2-}}\text{<}{\text{F}}^{\text{-}}\text{<}{\text{OH}}^{\text{-}}\text{<}{\text{O}}^{\text{2-}}\text{<}{\text{H}}_{\text{2}}\text{O}\text{<}{\text{NCS}}^{\text{-}}\text{<}{\text{edta}}^{\text{4-}}\text{<}{\text{NH}}_{\text{3}}\text{< en}\text{<}{\text{NO}}^{\text{2-}}\text{<}{\text{CN}}^{\text{-}}\text{<}\text{CO}}}{\to }\\ {}_{{}^{{}^{\begin{array}{l}\text{weak-field}\text{increasing(Δ)}\text{strong-field}\\ \text{ligands}\text{ligands}\end{array}}}}\end{array}$

The strong-field ligands results in pairing of electrons present in the complex and leads to diamagnetic species, while the low-field ligand do not have tendency to pair up the electrons therefore forms paramagnetic species.

Crystal Field Theory: It is the next advancement of valence bond theory which helps to understand the bonding in coordination complexes, identify the spin of the complex that is whether it will be a high spin or low spin and to find the color of the complex.

In crystal field theory the five d orbitals get divided into two sets that is ${\text{d}}_{\text{xy}}{\text{, d}}_{\text{yz}}{\text{ and d}}_{\text{xz}}$ orbitals forms one set and ${\text{d}}_{{\text{x}}^{\text{2}}{\text{-y}}^{\text{2}}}{\text{and d}}_{{\text{z}}^{\text{2}}}$ forms another set. The first set are oriented between the x, y and z axes whereas the second set gets oriented along the axis.

(b)

Interpretation Introduction

Interpretation:

The structure of paramagnetic $NiC{l}_2{L}_2$ and diamagnetic $Ni{\left(NCS\right)}_2{L}_2$ should be identified.

(c)

Interpretation Introduction

Interpretation:

The structure of $Ni{X}_2{L}_2$ complex that has dipole moment should be identified.