Chapter 20, Problem 20.137CHP

a)

Interpretation Introduction

Interpretation:

The systematic name for ${\text{Na}}_2\left[\text{Fe}{\left(\text{CN}\right)}_5\text{NO}\right]$ and oxidation state of Iron has to be predicted.

Concept Introduction:

Naming coordination compounds:

1. 1) Name the cation first and then anion.
2. 2) When naming the name of the complex ion or molecule, name the ligands first, in alphabetical order, followed by the name of the metal.
3. 3) If the coordination complex is an anion, the suffix-ate is added to the metal name.
4. 4) Following the name of the metal, the oxidation state of the metal is given in roman numerals.

b)

Interpretation Introduction

Interpretation:

The crystal field energy level diagrams for ${\text{Na}}_2\left[\text{Fe}{\left(\text{CN}\right)}_5\text{NO}\right]$ has to be drawn, the electron to orbitals has to be assigned, and number of unpaired electrons has to be predicted.

Concept Introduction:

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.

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.

Ligand field theory: It is used to explain the bonding between metal and ligand in a coordination complex. Ligand field theory is explained in terms of electrostatic interaction of between metal ion and ligands.

$Spectrochemical$ 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 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.