Chapter 22, Problem 29PS

Interpretation Introduction

Interpretation: The reason behind the given statement that is the $Ni$ in ${\left[Ni\left(C{N}_4\right)\right]}^{2-}$ is diamagnetic whereas the same metal in ${\left[Ni\left(C{l}_4\right)\right]}^{2-}$ will be paramagnetic has to be explained.

Concept introduction: The transition metal atoms have tendency to form complex compounds that are linked to the certain neutral or ionic species which leads to the formation of coordination compounds. There exists a large number of coordination compounds that have a large number of applications in the chemical industry as well as in daily life.

The properties of the coordination compounds depend upon the primary and secondary valancy of the metal ion in the coordination sphere. The electrical conductivity depends upon the number of ions that are produced by complex.

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

Ligands: The ions or molecules that forms coordination covalent bond with metal ions in a coordination compound. Ligands should have minimum one lone pair of electron, where it donates two electrons to the metal. Metal atom accepts the electron pair from a ligand forming a coordination bond.

$Monodentate$ Ligand is ligand which donates only one pair of electrons to form bond with metal. It only makes one bond with metal. Polydentate ligand forms two or more coordination bond with metal ions to form a complex.

$Spectrochemical$ 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.

The strong field ligands lead to splitting to a higher extent than the weak field ligands and the wavelength of light absorbed depends on the energy gap that is produced by a particular ligand.

The five d orbitals get divided into two sets that are ${\text{d}}_{\text{xy}}{\text{, d}}_{\text{yz}}{\text{ and d}}_{\text{xz}}$ 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.