Question

Which of the following statements is incorrect for the coordination compound :
$K_2\left[Cr\right(NO\left)\right(N{H}_3\left)\right(CN{)}_4]$?

• A. Its IUPAC name is potassium amminetetracyanonitrosonium chromate (I)
• B. Its spin only magnetic moment is $\sqrt{8}$ BM
• C. Its hybridisation is $d^{2}s{p}^3$
• D. It shows geometrical isomerism

Answer 1

The correct option is B Its spin only magnetic moment is $\sqrt{8}$ BM

a) The IUPAC name of the complex $K_2\left[Cr\right(NO\left)\right(N{H}_3\left)\right(CN{)}_4]$ is potassium amminetetracyanonitrosonium chromate (I).
b) Here chromium is in +1 oxidation state and since $C{N}^{-}$ and $N{H}_3$ are strong field ligands,they force pairing up the valence electron of $Cr$. Number of unpaired electrons will be 1. Hence spin only magnetic moment $\sqrt{1(1+2)}=\sqrt{3}$ BM.
c) The hybridisation of $\left[Cr\right(NO\left)\right(N{H}_3\left)\right(CN{)}_4{]}^{2-}$
takes place in the following manner

d) The geometry of $K_2\left[Cr\right(NO\left)\right(N{H}_3\left)\right(CN{)}_4]$ is octahedral. Since there are 3 different ligands present, it does not possess any plane of symmetry. Hence it shows geometrical isomerism.