CRYSTAL FIELD THEORY

Determine the coordination geometry of the metal complex based on the d-orbital splitting energy diagram

• Tetrahedral

• Octahedral

• Linear

• Square planar

Why do most tetrahedral complexes exhibit high-spin configurations?

• They have a strong ligand field, causing large orbital splitting

• They have six ligands, increasing the pairing energy

• Tetrahedral complexes always contain low-spin metal ions

• The crystal field splitting energy is small, so electrons prefer to occupy higher orbitals rather than pair

Why are square planar complexes generally not classified as high-spin or low-spin?

• They have no d-orbitals involved in bonding

• The splitting energy is too small

• All square planar complexes are tetrahedral in shape

• The strong crystal field causes complete pairing of electrons, making high-spin configurations unlikely

Why do e_g orbitals have higher energy in an octahedral complex?

• They are lower in energy

• They point directly at ligands, causing strong repulsion

• They have no interaction with ligands

• They are filled after the t₂g orbitals

Which of the following is a unique characteristic of octahedral complexes compared to square planar and tetrahedral complexes?

• They have the smallest number of coordination sites

• They exhibit both high-spin and low-spin configurations depending on ligand strength

• They always form low-spin configurations

• They cannot undergo crystal field splitting

Why does the d_x²–_y² orbital has the highest energy in a square planar complex?

• It mixes with the s-orbital

• It is farther from the nucleus

• It is unoccupied in all metal complexes

• It points directly at the ligands in the plane, causing strong repulsion

Which of the following complexes causes a larger crystal field splitting energy, and what is the correct reasoning?

• [Fe(H₂O)₆]²⁺, because it has more unpaired electrons

• Both have the same splitting energy since they have the same ligand

• [Fe(H₂O)₆]²⁺, because H₂O is a weak field ligand

• [Fe(H₂O)₆]³⁺, because the higher oxidation state increases attraction between the metal ion and ligands

Which of the following metal ions is expected to produce the largest crystal field splitting energy (Δ),

• [Cr(H₂O)₆]³⁺

• [Ru(H₂O)₆]³⁺

• [Mn(H₂O)₆]²⁺

• [Fe(H₂O)₆]²⁺

Between [Fe(en)₃]²⁺ and [FeF₆]⁴⁻, which complex is more likely to form a low-spin configuration, and why?

• [Fe(en)₃]²⁺, because ethylenediamine (en) is a strong field ligand that increases d-orbital splitting

• [FeF₆]⁴⁻, because fluoride is a weak field ligand that causes strong pairing of electrons

• [Fe(en)₃]²⁺, because Fe²⁺ always forms low-spin complexes regardless of ligand

• [FeF₆]⁴⁻, because fluorine has high electronegativity and attracts electrons more strongly