Inner Orbital Complex
Definition and meaning of Inner Orbital Complex in chemistry.
Inner orbital complex is a coordination compound in which the central metal ion uses inner (n-1)d orbitals, along with ns and np orbitals, to form hybrid orbitals for bonding to ligands, as described by valence bond theory.
In more detail
This hybridization pattern, typically d2sp3, arises when strong-field ligands force pairing of the metal ion's d electrons, which frees up two inner d orbitals for use in bonding. Because the d electrons are paired, inner orbital complexes are low-spin and usually have reduced or zero magnetic moment (often diamagnetic). This contrasts with outer orbital complexes, which use outer nd orbitals in sp3d2 hybridization with weak-field ligands and remain high-spin.
Key facts
| Typical hybridization | d2sp3 (uses (n-1)d, ns, np orbitals) |
|---|---|
| Ligand type required | Strong-field ligands (e.g., CN-, NH3, en) |
| Magnetic behavior | Low-spin; often diamagnetic |
| Field | Inorganic Chemistry |
In [Co(NH3)6]3+, Co3+ has a d6 configuration. NH3, a strong-field ligand, causes all six d electrons to pair into three of the five 3d orbitals, leaving two empty inner 3d orbitals that combine with one 4s and three 4p orbitals to give d2sp3 hybrid orbitals. The resulting octahedral complex is low-spin and diamagnetic.
Frequently asked questions
What is the difference between an inner orbital complex and an outer orbital complex?
Inner orbital complexes use (n-1)d orbitals in hybridization (d2sp3) because strong-field ligands pair up the metal's d electrons, giving low-spin complexes. Outer orbital complexes use outer nd orbitals (sp3d2) with weak-field ligands, leaving electrons unpaired and giving high-spin complexes.
Is [Co(NH3)6]3+ an inner orbital complex?
Yes. NH3 is a strong-field ligand, so Co3+ (d6) pairs its electrons and undergoes d2sp3 hybridization using inner 3d orbitals, forming a low-spin, diamagnetic octahedral complex.