Coordination Chemistry

Bidentate Ligands

• A bidentate ligand has two ends (coordination atoms) that bind to the central metal ion, represented by A and B.
• The straight line connecting the two groups trans to each other passes through the center where the metal ion is placed.

[M(AA)2]n Type Complexes

• [M(AA)2]n type complexes have a central metal ion (M) and symmetrical bidentate ligands (AA).
• The central metal atom or ion makes available a number of empty s, p, and d atomic orbitals equal to its coordination number, which is 4.

Geometrical Orientations of d-Orbitals

• The five d-orbitals have specific geometrical orientations and shapes.

Crystal Field Splitting

• Crystal field splitting occurs due to the arrangement of ligands around the central metal ion.
• The arrangement of ligands affects the energy levels of the d-orbitals.

Octahedral Complexes

• In octahedral complexes, six ligands are arranged octahedrally around the central metal ion.
• The repulsive forces exerted by the ligands are strongest along the x, y, and z axes.
• Examples of octahedral complexes include [Fe(CN)6]3- and [Fe(H2O)6]3+.
• The crystal field splitting energy (Δ) and the pairing energy (P) are important parameters in octahedral complexes.
• Δ = 35,000 cm-1 and P = 22,000 cm-1 for [Fe(CN)6]3-.
• Δ = 13,700 cm-1 and P = 22,000 cm-1 for [Fe(H2O)6]3+.
• The energy level diagram shows the splitting of the d-orbitals into eg and t2g levels.