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First Ionization Energies of Transition Metals

First Ionization Energies of Transition Metals. The first ionization energy increases gradually from left to right on the periodic table. 5 d. 3 d. 4 d. Oxidation States of 3 d Transition Metals. Formation of Coordinate Covalent Bonds.

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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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