CHEM 108 1st Edition Lecture 30Chapter 17: Metal IonsSolubilities of Hydrated Complex Ions:- Most transition metal cations form insoluble hydroxides: o Fe(OH)3 (s) ⇌ Fe3+ (aq) + 3OH− (aq) Ksp = 1.1 × 10−36 o Al(OH)3 (s) ⇌ Al3+ (s) + 3OH− (aq) Ksp = 1.9 × 10−33 - For some, solubility increases in strongly basic solution: o Al(OH)3 (s) + OH− (aq) ⇌ Al(OH)4 − (aq) [Al(H2O)2 (OH)4 ] – o Cr(OH)3 (s) + OH− (aq) ⇌ Cr(OH)4 − (aq) [Cr(H2O)2 (OH)4 ] −Polydentate Ligands: - Monodentate ligand: Species that forms a single coordinate bond to a metal ion in a complex (NH3 , Cl− ). - Polydentate ligand: Species that can form more than one coordinate bond per molecule. - Chelation: Interaction of a metal ion with a ligand having multiple donor atoms (chelating agent).Ligand Displacement: - Ligands with a higher affinity for metal cation will displace ligands with less affinity- Ni(H2O)62+ + 6NH3 ⇌ Ni(NH3)6 2+ + 6H2O o Kf = 5 × 108 NH3 is a stronger Lewis base than H2O- When Ligands get replaced the colors of the complex ion change as well. - Chelate Effect: Greater affinity of metal ions for polydentate ligands than for monodentate ligands. o Ni(NH3)6 2+ + 3en ⇌ Ni(en)32+ + 6NH3 o Kf = 1.1 × 1018 o This is an Entropy-driven processCrystal Field Theory: - Crystal field splitting: Process of changing degenerate d-orbitals (same energy) into subsets with different energies as a result of interactions between electrons in those orbitals and lone pairs ofelectrons in ligands. - Crystal field splitting energy (Δ): The difference in energy between subsets of d orbitals split by interactions in a crystal field.- This also explains the color change when the ligands displace another ligand in a complex ionColor of complex Ion:- Color observed is complementary (opposite) of color of absorbed light.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Red is complementary to greeno Orange is complementary to Blueo Yellow is complementary to violet - This also depends on the wavelength of light that the complex ion absorbso Red has the lowest wavelength, and violet has the highest wavelength Spectrochemical Series: - Rank-ordering of ligands based on their ability to split d-orbital energies.- (weak-field ligands) I- < Br- < SCN- < Cl- < F- ≤ OH- , ONO- < OH2 < NCS- < NCCH3 < NH3 , py < NO2- < CN- , NO , CO (strong-field ligands)- Field strength is created by the repulsion force of the ligand with the central-ion electrons.- Crystal field splitting energy (Δ) increases as field strength increases.- High field strength ligands form complexes that absorb short wavelength, high energy light. - Low field strength ligands absorb long wavelength low energy light.Magnetic Properties:- Paramagnetism: Attraction to magnetic field; requires unpaired electrons. The more unpaired electrons the more paramagnetic. - High-spin state: Low field strength = small Δ. Maximize unpaired electrons. o Ex: five unpaired electrons- Low-spin state: High field strength = large Δ. Minimize unpaired electrons.o Ex: one unpaired electronFor Octaheral shaped complexes if the ligand has high field strength then it is in low spin state. But if the ligand has low field strength then it is in high spin
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