Chemistry (Chang), 9th Edition

Chapter 22: Transition Metal Chemistry and Coordination Compounds

Chapter Summary

1. Transition metals usually have incompletely filled d subshells and a pronounced tendency to form complexes. Compounds that contain complex ions are called coordination compounds.

2. The first-row transition metals (scandium to copper) are the most common of all the transition metals; their chemistry is characteristic, in many ways, of the entire group.

3. Complex ions consist of a metal ion surrounded by ligands. The donor atoms in the ligands each contribute an electron pair to the central metal ion in a complex.

4. Coordination compounds may display geometric and/or optical isomerism.

5. Crystal field theory explains bonding in complexes in terms of electrostatic interactions. According to crystal field theory, the d orbitals are split into two higher-energy and three lower-energy orbitals in an octahedral complex. The energy difference between these two sets of d orbitals is the crystal field splitting.

6. Strong-field ligands cause a large crystal field splitting, and weak-field ligands cause a small splitting. Electron spins tend to be parallel with weak-field ligands and paired with strong-field ligands, where a greater investment of energy is required to promote electrons into the high-lying d orbitals.

7. Complex ions undergo ligand exchange reactions in solution.

8. Coordination compounds find application in many different areas, for example, as antidotes for metal poisoning and in chemical analysis.