Question

Which of the following will form an octahedral complex?

• A. d⁵ low spin
• B. d⁸ high spin
• C. d⁴ low spin
• D. all of these

Answer 1

The correct option is A

d⁵ low spin

Explanation for correct option

(A) d⁵ low spin

• The octahedral complex will be formed by d⁵ low spin.
• With 5d orbitals, $3$ will contain electrons and $2$ will remain empty having the configuration ${{\mathrm{t}}_{2\mathrm{g}}}^5{{\mathrm{e}}_{\mathrm{g}}}^0$.
• These empty d orbitals can undergo ${\mathrm{sp}}^3{\mathrm{d}}^2$ hybridization and form an octahedral complex.
• The complex having hybridization ${\mathrm{sp}}^3{\mathrm{d}}^2$ would consist of octahedral shape.

Explanation for incorrect option

(B) d⁸ high spin

• It can not undergo ${\mathrm{sp}}^3{\mathrm{d}}^2$ hybridization.
• Thus cannot form an octahedral complex.

(C)d⁴ low spin

• It can not undergo sp³d² hybridization and thus cannot form an octahedral complex.

Hence, option (A) is correct., d⁵ low spin will form an octahedral complex.