Question

Write down the IUPAC name for each of the following complexes and indicate the oxidation state, electronic configureation and coordination number. Also give stereochemistry and magnetic moment of the complex:
$K\left[Cr\right(H_{2}O{)}_2\left(C_2{O}_4{)}_2\right].3H_{2}O$

$\left[Co\right(N{H}_3{)}_{5}Cl]C{l}_2$

$CrC{l}_3(py{)}_3$

$Cs\left[FeC{l}_4\right]$

$K_4\left[M_n\right(CN{)}_6]$

Answer 1

$K\left[Cr\right(H_{2}O{)}_2\left(C_2{O}_4{)}_2\right].3H_{2}O$
IUPAC name: Potassium diaquadioxalatochromate (III) hydrate:
Coordination number (CN) = 6;
Shape = octahedral
Oxidation state of Cr
$\begin{array}{c}+1+x+\left(0\right)\times +(-2)2+3\left(0\right)=0\\ +1+x-4=0\\ x=+3\\ ElectronConfigurationofC{r}^{3+}=\left[Ar\right]3d^{3}4s^0=t_{2g}^3.e_g^0\end{array}$
Unpaired electrons (n) = 3
Magnetic moment $\left(\mu \right)=\sqrt{n(n+2)}=\sqrt{3(3+2)}=3.87$ BM
This complex exhibits geometrical isomerism and exists in following cis-trans forms.

cis-form can be resolved into d and l-forms (i.e., optical isomers)

$\left[Co\right(N{H}_3{)}_{5}Cl]C{l}_2$
IUPAC name: Pentaaamminechlorocobalt (III) chloride
Oxidation state of Co can be calulated as
$\begin{array}{c}x+\left(0\right)5+(-1)+(-1)2=0\\ x-3=0\\ x=+3\end{array}$
Coordination number (CN) = 5 + 1 = 6 (number of monodentate ligands)
Outer electronic configuration (EN) of $C{o}^{3+}=3d^6=t_{2g}^6{e}_g^0$
Number of unpaired electrons, n = 0 (all electrons are paired)
So, magnetic moment, $\mu =\sqrt{n(n+2)}BM$
$=\sqrt{0(0+2)}$ BM = 0 BM
This complex does not exhibit geometrical as well as optical isomerism.

$CrC{l}_3(py{)}_3$
IUPAC name: Trichlorotripyridinechromium (III)
Oxidation state of Cr
$\begin{array}{c}x+(-1)\times 3+\left(0\right)3=0\\ x=+3\end{array}$
Coordination number (CN) = 6
Outer electronic configuration of Cr =$3d^3\left(t_{2g}^3{e}_g^0\right)$
Number of unpaired electrons = 3
So, magnetic moment, $\mu =\sqrt{n(n+2)}$ BM
$=\sqrt{3(3+2)}=\sqrt{15}=3.87BM$
This complex exists in fac and mer forms, i.e., exhibit geometrical isomerism, (In fac form, similar groups occupy adjacent positions while this is not true in case of mer-isomer.

$Cs\left[FeC{l}_4\right]$
IUPAC name: Caesium tetrachloroferrate (III)
Oxidation state of Fe
$\begin{array}{c}+1+x+(-1)4=0\\ x-3=0\\ x=+3\end{array}$
Coordination number, (CN) = 4
Outer electronic configuration of Fe = $3d^5\left(t_{2g}^3{e}_g^2\right)$
Number of unpaired electrons = 5
$\therefore$ Magnetic moment, $\begin{array}{c}\mu =\sqrt{n(n+2)}BM\\ =\sqrt{5(5+2)}=\sqrt{35}=5.92BM\end{array}$
It is a tetrahedral complex, so it does not exhibit geometrical or optical isomerism, (stereo isomerism).

$K_4\left[M_n\right(CN{)}_6]$
IUPAC name: Potassium hexacyanomanganate (II)
Oxidation state of Min in $K_4\left[Mn\right[CN{]}_6$ ]
$\begin{array}{c}(+1)4+x+(-1)6=0\\ x-2=0\\ x=+2\end{array}$
Coordination number (CN) = 6
Outer electronic configuration of Mn = $3d^{5\left[t_{2g}^5{e}_g^0\right]}$
(as $C{N}^{-}$ is a strong field ligand)
Number of unpaired electrons = 1
Magnetic moment,
$\begin{array}{c}\mu =\sqrt{n(n+2)}BM=\sqrt{1(1+2)}BM\\ =\sqrt{3}=1.73BM\end{array}$
This complex does not exhibit stereo isomerism.
Note d-orbitals split up into $t_{2g}\left(d_{xy,}{d}_{yz,}{d}_{2x}\right)$ set and $\left(e_g\right(d_{2^1}^2{d}_{x^2-y^2})$ set as.