Assertion (A): $\left[Cr\left({H}_{2}{O}_{6}\right)\right]C{l}_{2}$ and $\left[Fe{\left({H}_{2}O\right)}_{6}\right]C{l}_{2}$ are reducing in nature.

Reason (R): Unpaired electrons are present in their d-orbitals.

1.  Both assertion and reason are true and the reason is the correct explanation of assertion.

2.  Both assertion and reason are true and reason is not the correct explanation of assertion.

3.  Assertion is true but the reason is false.

4.  Assertion is false but reason is true.

Hint: Both can show a +3 oxidation state

Assertion and reason both are true but the reason is not correct explanation for the assertion.
$\left[Cr\left({H}_{2}{O}_{6}\right)\right]C{l}_{2}$ and $\left[Fe{\left({H}_{2}O\right)}_{6}\right]C{l}_{2}$ are reducing in nature due to formation of more stable complex ion after gaining of electron.