First Ionization Energies of Transition Metals The first

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First Ionization Energies of Transition Metals • The first ionization energy increases gradually from

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 Element group Sc 3 Ti 4 V

Oxidation States of 3 d Transition Metals Element group Sc 3 Ti 4 V 5 Cr 6 Oxidation state Key Mn 7 Fe 8 Co 9 Ni 10 Cu 11 Zn 12 Valance configuration +1 d 4 d 5 d 6 d 7 d 8 d 9 d 10 +2 d 1 d 2 d 3 d 4 d 5 d 6 d 7 d 8 d 9 d 10 +3 d 0 d 1 d 2 d 3 d 4 d 5 d 6 d 7 d 8 +4 d 0 d 1 d 2 d 3 d 4 d 5 d 6 +5 d 0 d 1 d 2 d 3 d 4 +6 d 0 d 1 d 2 +7 d 0 +2 +3 +4 d 0 *Table lists the configuration of the ion corresponding to each observed oxidation state. The most important oxidation states of each element are color screened.

Formation of Coordinate Covalent Bonds • A ligand donates a lone pair of electrons

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(NH 3)6]2+ form by overlap of the lone pair sp 3 orbital on the nitrogen atom with an empty valence orbital on the metal. Donor Metal

2+ Two Ni -Ligand Complexes • Both water and ammonia form six covalent bonds

2+ Two Ni -Ligand Complexes • Both water and ammonia form six covalent bonds with Ni 2+, resulting in octahedral geometry.

Colors of Two Ni 2+-Ligand Complexes [Ni(H 2 O)6]2+ [Ni(NH 3)6]2+

Colors of Two Ni 2+-Ligand Complexes [Ni(H 2 O)6]2+ [Ni(NH 3)6]2+

Coordination Number - Two • Complexes with coordination number two always adopt linear geometry

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

Coordination Number – Four Tetrahedral and Square planar

Coordination Number – Four Tetrahedral and Square planar

Coordination Number – Six Octahedral

Coordination Number – Six Octahedral

Bidentate Ligands

Bidentate Ligands

Heme • Oxygen-carrying component of blood. • Planar structure. • Multi-ring structure of C

Heme • Oxygen-carrying component of blood. • Planar structure. • Multi-ring structure of C and N atoms. • Extensive delocalized π system. • Binds one Fe 2+ cation at its center. Iron

Repulsion of Ligand Electrons and Metal Electrons is Greatest with Overlap • dx 2–y

Repulsion of Ligand Electrons and Metal Electrons is Greatest with Overlap • dx 2–y 2 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 dxy orbital dx 2–y 2 orbital

The Five d Orbitals Interacting with an Octahedral Set of Ligands

The Five d Orbitals Interacting with an Octahedral Set of Ligands

The Crystal Field Level Diagram for Octahedral Coordination Complexes • Electron-cation attraction stabilized all

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.

Crystal Field Splitting Energy • Crystal field splitting energy: – The difference in energy

Crystal Field Splitting Energy • Crystal field splitting energy: – The difference in energy between the eg and t 2 g sets. – Symbolized by the Greek letter, Δ. dz 2 dx 2–y 2 Δ dxy eg dxz dyz t 2 g

The Spectrochemical Series • The spectrochemical series lists the common ligands in order of

The Spectrochemical Series • The spectrochemical series lists the common ligands in order of increasing ability to split the energies of the t 2 g 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.

Relationships Among Wavelength, Color, and Crystal Field Splitting Energy (Δ) Wavelength (nm) Color absorbed

Relationships Among Wavelength, Color, and Crystal Field Splitting Energy (Δ) Wavelength (nm) Color absorbed Complementary color Δ (k. J/mol) >720 Infrared Colorless <165 720 Red Green 166 680 Red-orange Blue-green 176 610 Orange Blue 196 580 Yellow Indigo 206 560 Yellow-green Violet 214 530 Green Purple 226 500 Blue-green Red 239 480 Blue Orange 249 430 Indigo Yellow 279 410 Violet Lemon-yellow 292 <400 Ultraviolet Colorless >299

Colors of Cr 3+ Coordination Complexes • The colors of Cr 3+ coordination complexes

Colors of Cr 3+ Coordination Complexes • The colors of Cr 3+ 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.