Question

Which of the following statements is correct for complex $\left[Cr\right(N{H}_3\left)\right(CN{)}_4\left(NO\right){]}^{2-}$ (given that n $=$ 1)?

• A. It is $d^{2}s{p}^3$ hybridised
• B. The chromium is in +I oxidation state
• C. It is heteroleptic complex and its aqueous solution is coloured
• D. All of these.

Answer 1

The correct option is D All of these.

All of the following statements are correct for complex $\left[Cr\right(N{H}_3\left)\right(CN{)}_4\left(NO\right){]}^{2-}$ (given that n $=$ 1).
(A) It is $d^{2}s{p}^3$ hybridised.
Cr has valence shell electronic configuration $3d^{5}4s^1$
Cr(I) has valence shell electronic configuration $3d^{5}4s^0$. It can also be written as $t_{2g}^5{e}_g^0$.
Two 3d orbitals, one 4s and three 4p orbitals undergo $d^{2}s{p}^3$ hybridization to form octahedral geometry around chromium.
(B) The chromium is in +I oxidation state.
Let X be the oxidation state of Cr in the complex.
$X+0+4(-1)+1=-2$
$X=+1$
(C) It is heteroleptic complex (as it contains more than one type of ligand) and its aqueous solution is coloured due to presence of one unpaired electron.