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Chemistry and Spectroscopy of the Transition Metals

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Chemistry and Spectroscopy of the Transition Metals Chemistry and Spectroscopy of the Transition Metals • Structure of metal complexes • Oxidation states of metals • Color/Spectroscopy • Magnetic Properties • Chelate Effects • Electron Transfer Chemistry Nobel Prize in Chemistry, 1913 Alfred Werner "in recognition of his work on the linkage of atoms in molecules by which he has thrown new light on earlier investigations and opened up new fields of research especially in inorganic chemistry” Zurich University Stereochemistry of Coordination Complexes Pt (NH3)2Cl2 Cl NH 3 NH3 Cl Pt Pt Cl NH Cl 3 NH3 Orange-Yellow Pale Yellow (dipole moment) No dipole (cis-platin) Inner Sphere vs Outer Sphere Coordination H3 H3 N N NH H N NH H3N 3 [Cl- ] 3 3 - Co 3 Co [Cl 2] H N NH3 H N NH3 [ 3 ] [ 3 ] N Cl H3 H3 H3 N N Cl H3N Cl H3N Co [Cl- ] Co [Cl-] H N Cl Cl NH3 [ 3 ] N [ N ] H3 H3 Transition Metal Chemistry • Multiple Oxidation States • Coordination Chemistry/Stereochemistry • Crystal Field Splitting: Optical and Magnetic Properties • Ligand Field Splitting: Spectrochemical Series • Distortion to Tetragonal, Square Planar • Ligand Field Stabilization Energy • Hard and Soft Acids and Bases • Chelate Effect • Stereochemical Control of Binding Affinity • Water Exchange • Electron Exchange Organization of Periodic Chart 1s 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 5d 6p 7s 6d 4f 5f Shielding r2Ψ2 1s 3d 3p 3s Penetration: 3s > 3p > 3d r 3d orbitals are shielded and not exposed much; Outside world won’t know as much how many d e- there are Transition Metals Are Found in Several Oxidation States Charge to mass ratio - of ions: current e which passes through circuit divided by mass gained on electrode. Ammeter Faraday (1830): discovered this phenomenon and determined the charge to mass ratio of ions M+ M+ M+ M+ Transition Metals Are Found in Several Oxidation States Charge to mass ratio - of ions: current e which passes through circuit divided by mass gained on electrode. Ammeter Fe(II) Fe(III) Fe(IV) Indicate oxidation state by Roman numerals in M+ parentheses M+ M+ M+ Exceptions to Filling Order H 2s 2p He 3s 3p Li Be 4s B C N O F Ne Na Mg 3d 4p Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr 2 3 23. V (4s) (3d) ↑ ↑ ↑ ↑ 1 5 3d 24. Cr (4s) (3d) 4s ↑↓ 25. Mn (4s)2(3d)5 higher energy Exceptions occur because electrons don’t like to pair up Cr(0) ground state in orbitals; so the highlighted ↑ ↑ ↑ ↑ 3d ↑ ↑ atoms have lower energy. 4s All Metal Ions Have dn Configurations H 2s 2p He 3s 3p Li Be 4s B C N O F Ne Na Mg 3d 4p Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr 23. V (4s)2(3d)3 Cr(0) ground state 24. Cr (4s)1(3d)5 3d ↑ ↑ ↑ ↑ ↑ 25. Mn (4s)2(3d)5 4s ↑ Cr(III) (4s)1(3d)2? - -3e Cr(III) ground state NO: (3d)3 (4s)0 4s 4s becomes higher than 3d 3d ↑ ↑ ↑ in all of the metal ions All Metal Ions Have dn Configurations H 2s 2p He 3s 3p Li Be 4s B C N O F Ne Na Mg 3d 4p Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr 40. Zr (5s)2(4d)2 Zr(0) ground state 41. Nb (5s)1(4d)4 ↑ 4d ↑ ↑ 42. Mo (5s)1(4d)5 5s ↑ - Zr(II) (4d)2 (5s)0 -3e Zr(II) ground state 5s 4d ↑ ↑ All Metal Ions Have dn Configurations H 2s 2p He 3s 3p Li Be 4s B C N O F Ne Na Mg 3d 4p Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr 40. Zr (5s)2(4d)2 Nb(0) ground state 41. Nb (5s)1(4d)4 4d ↑ ↑ ↑ ↑ 42. Mo (5s)1(4d)5 5s ↑ - Zr(II) (4d)2 (5s)0 -3e Nb(III) ground state 2 0 Nb(III) (4d) (5s) 5s Mo(IV) (4d)2(5s)0 4d ↑ ↑ Transition Metal Chemistry • Multiple Oxidation States • Coordination Chemistry/Stereochemistry • Crystal Field Splitting: Optical and Magnetic Properties • Ligand Field Splitting: Spectrochemical Series • Distortion to Tetragonal, Square Planar • Ligand Field Stabilization Energy • Hard and Soft Acids and Bases • Chelate Effect • Stereochemical Control of Binding Affinity • Water Exchange • Electron Exchange Cr(III) Cr(III) Reactions of Coordination Complexes 2+ 2+ 8 [Ni(H2O)6 ] + 6 NH3 [Ni(NH3)6 ] + 6 H2O Ni(II) d Green Blue-violet 2+ 4- 6 Fe(H2O)6 + 6 K(CN) K4[Fe(CN)6] + 6 H2O Fe(II) d 3+ 3- + 5 Fe(H2O)6 + 6 K(CN) K4[Fe(CN)6] + 6 H2O + 2 K Fe(III) d 2+ 2- + 9 Cu(H2O)4 + 4 KCl K2[CuCl4] + 4 H2O + 2 K Cu(II) d Oxidation state stays the same Colors are very different + [Co(NH3)4Cl2] 3+ 2+ [Co(NH3)6] [Co(NH3)5Cl] Nobel Prize in Physics, 1966 Hans Bethe, Cornell Discovery of the C/N cycle that supplies energy to brilliant stars, 1935-1938 Atomic physics and collision theory Nuclear forces acting on the nucleon Lamb shift in the H-spectrum; modern quantum electrodynamics Π mesons and their production by electromagnetic radiation Crystal Field theory: 1929 Crystal Field Splitting Octahedral Complexes z2 x2-y2 Non-spherical ∆o symmetry Extra electron density xz yz xy d O C O C O C Cr CO C O C O Spectrochemical Series I- < Br - < Cl - < F - σ Donors z2 x2-y2 z2 x2-y2 ∆o ∆o xz yz xy xz yz xy Colors of Minerals/Gemstones beryllium Yellow beryl aluminum silicate (Heliodor) is colored Be2Al2Si6Ol8 by the presence of F3+ ions. Beryl includes emerald , aquamarine, and lesser known varieties: goshenite (colorless), morganite (pink), Heliodor (yellow), and bixbite (red). Red ruby. The name ruby comes from the Cr(III) in Al2O3 Latin "Rubrum" meaning red. The ruby is in the Corundum group, along with the sapphire. The brightest red and thus most valuable rubies are usually from Burma. Violet Green emerald. The mineral is transparent emerald, the green Cr(III) in Be2Al2Si6Ol8 variety of Beryl on calcite matrix. 2.5 x 2.5 cm. Coscuez, Boyacá, Colombia Spectrochemical Series z2 x2-y2 z2 x2-y2 ∆o ∆o xz yz xy xz yz xy 2+ 2+ 3+ 2+ 2+ 3+ 3+ ∆o: Mn < Ni < Rh < Co <Fe <Fe <Cr < Co3+ <Ir3+ < Pt4+ Transition Metal Chemistry • Multiple Oxidation States • Coordination Chemistry/Stereochemistry • Crystal Field Splitting: Optical and Magnetic Properties • Ligand Field Splitting: Spectrochemical Series • Distortion to Tetragonal, Square Planar • Ligand Field Stabilization Energy • Hard and Soft Acids and Bases • Chelate Effect • Stereochemical Control of Binding Affinity • Water Exchange • Electron Exchange Magnetic Properties of Octahedral Complexes - - - - - - I < Br < Cl < F < OH < H2O < NH3 < CN <CO d1 z2 x2-y2 z2 x2-y2 ∆o ∆o xz yz xy xz yz xy High Spin Low Spin Magnetic Properties of Octahedral Complexes - - - - - - I < Br < Cl < F < OH < H2O < NH3 < CN <CO d2 z2 x2-y2 z2 x2-y2 ∆o ∆o xz yz xy xz yz xy High Spin Low Spin Magnetic Properties of Octahedral Complexes - - - - - - I < Br < Cl < F < OH < H2O < NH3 < CN <CO d3 z2 x2-y2 z2 x2-y2 ∆o ∆o xz yz xy xz yz xy High Spin Low Spin Magnetic Properties of Octahedral Complexes - - - - - - I < Br < Cl < F < OH < H2O < NH3 < CN <CO d4 z2 x2-y2 z2 x2-y2 ∆o ∆o xz yz xy xz yz xy High Spin Low Spin Magnetic Properties of Octahedral Complexes - - - - - - I < Br < Cl < F < OH < H2O < NH3 < CN <CO d5 z2 x2-y2 z2 x2-y2 ∆o ∆o xz yz xy xz yz xy High Spin Low Spin Magnetic Properties of Octahedral Complexes - - - - - - I < Br < Cl < F < OH < H2O < NH3 < CN <CO d6 z2 x2-y2 z2 x2-y2 ∆o ∆o xz yz xy xz yz xy High Spin Low Spin Magnetic Properties of Octahedral Complexes - - - - - - I < Br < Cl < F < OH < H2O < NH3 < CN <CO d7 z2 x2-y2 z2 x2-y2 ∆o ∆o xz yz xy xz yz xy High Spin Low Spin Magnetic Properties of Octahedral Complexes - - - - - - I < Br < Cl < F < OH < H2O < NH3 < CN <CO d8 z2 x2-y2 z2 x2-y2 ∆o ∆o xz yz xy xz yz xy High Spin Low Spin Magnetic Properties of Octahedral Complexes - - - - - - I < Br < Cl < F < OH < H2O < NH3 < CN <CO d9 z2 x2-y2 z2 x2-y2 ∆o ∆o xz yz xy xz yz xy High Spin Low Spin Magnetic Properties of Octahedral Complexes - - - - - - I < Br < Cl < F < OH < H2O < NH3 < CN <CO d10 z2 x2-y2 z2 x2-y2 ∆o ∆o xz yz xy xz yz xy High Spin Low Spin Crystal Field Theory For Tetrahedral Complexes Crystal Field Splitting Tetrahedral Complexes xz yz xy ∆t z2 x2-y2 d ∆t= -4/9 ∆o Crystal Field Splitting Octahedral Complexes z2 x2-y2 ∆o xz yz xy d z2 x2-y2 Crystal Field Splitting Octahedral Complexes xz yz xy ∆t z2 x2-y2 d z2 x2-y2 z2 x2-y2 xz ∆o xz yz xy yz xy xz yz xy xz ∆t z2 x2-y2 yz xy Crystal Field Splitting Tetrahedral Complexes xz yz xy ∆t z2 x2-y2 d ∆t= -4/9 ∆o No low spin tetrahedral complexes Transition Metal Chemistry • Multiple Oxidation States • Coordination Chemistry/Stereochemistry • Crystal Field Splitting: Optical and Magnetic Properties • Ligand Field Splitting: Spectrochemical Series • Ligand Field Stabilization Energy • Chelate Effect • Stereochemical Control of Binding Affinity • Electron Exchange Ligand Field Stabilization Energy High Spin Octahedral Complexes z2 x2-y2 3/5 ∆o Non-spherical ∆o symmetry Extra electron density 2/5 ∆ xz yz xy o d dn ∆ H2O o 1 6 H2O H O d , d 2/5 2 2 7 M d , d 4/5 3 8 H O d , d 6/5 H2O 2 4 9 H O d , d 3/5 2 d0, d5, d10 0 Ligand Field Stabilization Energy 2+ 2+ M (g) + ∞ H2O [M(H2O)6] 3000 Hydration Energy (kJ/mol) 2500 Ca
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