Question

The complex [Cr(NH₃)₆]³⁺ involves d²sp³ hybridisation of the central metal ion. State whether it is an inner orbital or an outer orbital complex.

Answer 1

• The complex [Cr(NH₃)₆]³⁺ involves d²sp³ hybridisation of the central metal ion, chromium in the +3 oxidation state (Cr³⁺).
• Chromium has the electron configuration [Ar] 3d⁵ 4s², and upon losing three electrons to form Cr³⁺, its electron configuration becomes [Ar] 3d³.
• In this complex, Cr³⁺ uses two 3d orbitals, one 4s orbital, and three 4p orbitals to form six hybrid orbitals.
• Since the hybridisation involves the 3d orbitals from the third energy level (n = 3), this complex is classified as an inner orbital complex.
• The inner orbital complex classification arises because the hybridisation takes place using d orbitals from the inner shell, unlike the outer orbitals, which would be involved in an outer orbital complex.

Therefore, [Cr(NH₃)₆]³⁺ is an inner orbital complex due to the involvement of the inner 3d orbitals in its bonding.