Inner vs Outer Orbital Complexes: Key Differences Explained
Inner orbital complexes use low-spin configurations and (n-1)d orbitals, while outer orbital complexes use high-spin and nd orbitals in coordination compounds.
Chem students confuse them because both describe metal-ligand arrangements, yet textbooks swap terms casually and exam questions expect you to spot the subtle orbital choice difference.
Key Differences
Inner: strong-field ligands, low-spin, smaller unpaired electrons, uses inner d. Outer: weak-field ligands, high-spin, larger unpaired electrons, uses outer d.
Which One Should You Choose?
Pick inner for strong ligands like CN⁻ seeking stability; choose outer for weak ligands like H₂O favoring magnetism in practical synthesis.
Examples and Daily Life
K₄[Fe(CN)₆] is inner, low-spin, diamagnetic; [Fe(H₂O)₆]Cl₃ is outer, high-spin, paramagnetic—your MRI contrast agent needs the latter.
Does oxidation state decide the complex type?
Not alone; ligand field strength and metal identity matter more.
Can a complex switch between types?
Rarely; changing ligands or temperature can flip spin states.