1. Crystal stabilization energy (CFSE) CFSE = Energy lowering in the "crystal field" of the ligands, e.g., in an octahedral or tetrahedral complex Compare the CFSE for [Cr(CN) 6 ] 4- and [Cr(H 2 O) 6 ] 2+ What are the rules for high spin vs. low spin?

2. Crystal stabilization energy (CFSE) Hydration enthalpies of M 2+ ions Can you explain the trends?

3. Magnetic Susceptibility Molecules and ions that contain unpaired electrons are paramagnetic We can count the number of spins by measuring the susceptibility magnetic moment: µ ≈ µ spin = [n(n+2)] 1/2 µ Bohr What µ s values would you expect for Ni 2+ and Cu 2+ ?

4. When octahedra are distorted, the resulting geometries change the energies of the e g and t 2g orbitals (break degeneracy) Non-octahedral complexes Octahedron Elongated octahedron Square pyramid Square plane

5. d 8 (and d 9 ) are special electron counts for square planar complexes Non-octahedral complexes ΔOΔO dx 2 -y 2 dz 2 dxy dxz dyz Which metals (with which ligands) will form square planar complexes?

6. Square planar complexes are important in homogeneous catalysis Non-octahedral complexes Catalytic hydrogenation of olefins using Wilkinson's catalyst

7. What splitting pattern would you predict for a tetrahedral complex? Non-octahedral complexes

8. Tetrahedral complexes Co[CoCl 4 ] + 12 H2O ---> 2 Co(H 2 O) 6 Cl 2 (deep blue, tetrahedral CoCl 4 2- ) (light pink, octahedral [Co(H 2 O) 6 ] 2+ ) Why are tetrahedral complexes more strongly colored than octahedral ones?

9. Jahn-Teller Effect Complexes with unequal populations of electrons in upper (antibonding) orbitals distort to lower their energy [Cu(OH 2 ) 6 ] 2+ [Cu(OH 2 ) 5 ] 2+

10. Chelate and Macrocyclic Effects Multidentate ("chelating") ligands make very stable complexes What is different about these reactions?? Metal-en complexation [Co(H 2 O) 6 ] 2+ + 6 NH 3 ⇌ [Co(NH 3 ) 6 ] 2+ + 6 H 2 O [Co(H 2 O) 6 ] 2+ + 3 en ⇌ [Co(en) 3 ] 2+ + 6 H 2 O

11. Chelate and Macrocyclic Effects Chelating ligands EDTA 2,2'-bipyridine = bpy acetylacetonate = acac

12. Chelate and Macrocyclic Effects Macrocyclic ligands Valinomycin 18-crown-6 Heme b