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First Ionization Energies of Transition Metals

Understand the complexities of transition metals, ionization energies, oxidation states, and color changes in coordination complexes. Dive into ligand bonding, crystal field splitting, and spectrochemical series.

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First Ionization Energies of Transition Metals

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  1. First Ionization Energies of Transition Metals • The first ionization energy increases gradually from left to right on the periodic table. 5d 3d 4d

  2. Oxidation States of 3d Transition Metals

  3. Formation of Coordinate Covalent Bonds • A ligand donates a lone pair of electrons to form a bond to a metal. • Ex. The Ni–N bonds in [Ni(NH3)6]2+ form by overlap of the lone pair sp3 orbital on the nitrogen atom with an empty valence orbital on the metal. Donor Metal

  4. Two Ni2+-Ligand Complexes • Both water and ammonia form six covalent bonds with Ni2+, resulting in octahedral geometry.

  5. Colors of Two Ni2+-Ligand Complexes [Ni(H2O)6]2+ [Ni(NH3)6]2+

  6. Coordination Number - Two • Complexes with coordination number two always adopt linear geometry about the metal cation.

  7. Coordination Number – Four Tetrahedral and Square planar

  8. Coordination Number – Six Octahedral

  9. Bidentate Ligands

  10. Heme Iron • Oxygen-carrying component of blood. • Planar structure. • Multi-ring structure of C and N atoms. • Extensive delocalized π system. • Binds one Fe2+ cation at its center.

  11. Repulsion of Ligand Electrons and Metal Electrons is Greatest with Overlap • dx2–y2 points directly toward the ligands. • Overlap results in increased repulsion. • dxy points between the ligands. • Lack of overlap results in less repulsion. y y x x dxyorbital  dx2–y2 orbital

  12. The Five d Orbitals Interacting with an Octahedral Set of Ligands

  13. The Crystal Field Level Diagram for Octahedral Coordination Complexes • Electron-cation attraction stabilized all five d orbitals. • Electron-electron repulsion destabilizes the five d orbitals by different amounts.

  14. Crystal Field Splitting Energy • Crystal field splitting energy: • The difference in energy between the eg and t2g sets. • Symbolized by the Greek letter, Δ. eg dz2 dx2–y2 Δ t2g dxy dxz dyz

  15. The Spectrochemical Series • The spectrochemical series lists the common ligands in order of increasing ability to split the energies of the t2g and eg subsets of orbitals. • The ranking of ligands is influenced most strongly by the donor atom: • Generally decreases across Row 2 of the periodic table. • Generally decreases down the halogen column. • Molecular orbital theory is best used to explain the trend.

  16. Relationships Among Wavelength, Color, and Crystal Field Splitting Energy (Δ)

  17. Colors of Cr3+ Coordination Complexes • The colors of Cr3+ coordination complexes depend on the magnitude of the crystal field splitting energy. • Higher Δ, shorter λ. • The spectrochemical series indicates the relative magnitude of Δ.

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