Question

Write down the IUPAC name for each of the following complexes and indicate the oxidation state, electronic configuration and coordination number. Also give stereochemistry and magnetic moment of the complex:
${K_4}[Mn{(CN)_6}]$

Answer 1

Hint: IUPAC (International Union of Pure and Applied Chemistry) has given some rules for the naming of coordination complexes which needs to be followed strictly. We will find the oxidation number of the central metal atom by the substitution method and by using the electronic configuration of the central metal atom or ion, we can find out the magnetic moment of the given complex.

Complete answer:
The rules given by the IUPAC to name the coordination complexes are as follows:
- The cationic part of the entity is named before the anionic part.
- The name of the ligands should be in alphabetical order and the prefix “-o” is added to their name instead of “-ide”.
- The name of the central metal atom in the cation part remains as such but in the anionic part, a prefix “-ate” is added to its name.
- The oxidation state of the central metal atom should be written after its name in the parenthesis.
We will first calculate the oxidation state of Manganese in the given compound by substituting the oxidation states of other species in the complex:
${K_4}[Mn{(CN)_6}]$
$4( + 1) + x + 6( - 1) = 0$
$x = + 2$
The oxidation state of $$Mn$$ is $ + 2.$
Therefore, the IUPAC name of the given compound is Potassium hexacyanomanganate(II).
Six ligands are attached to central metal atom or ion and hence, the coordination number is $6.$
Electronic configuration of $M{n^{2 + }}$ is:
$$1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}3{d^5}$$
Number of unpaired electrons in this given coordination species is $5.$
Magnetic moment, $\mu $ is calculated as:
$\mu = \sqrt {(n(n + 2))} $
Here, n is the number of unpaired electrons in the species. The value of n is $5.$
$\mu = \sqrt {(5(5 + 2))} $
$\mu = 1.732B.M.$
Now, all the ligands attached to the central metal atom or ion are the same, so we can say that the given complex is optically inactive.

Note:
We should remember that while calculating the magnetic moment of any coordination complex, we always insert the number of unpaired electrons present in it in the formula. And if the same kind of ligands are attached to the central metal atom or ion, it is considered as optically inactive because when the positions and angles of ligands are changed with respect to each other, it will not make any difference.