Ch23 coordination(a)


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Ch23 coordination(a)

  1. 1. Transition Metals and Coordination Chemistry Chapter 23
  2. 2. Transition MetalsSimilarities within a given period and within a given group.Last electrons added are inner electrons ( d’s, f’s).
  3. 3. 20_431 Sc Ti V Cr Mn Fe Co Ni Cu Zn Y Zr Nb Mo Tc Ru Rh Pd Ag Cd La Hf Ta W Re Os Ir Pt Au Hg Ac Unq Unp Unh Uns Uno Une Uun Uuu 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
  4. 4. 20_432 d-block transition elements Sc Ti V Cr Mn Fe Co Ni Cu Zn Y Zr Nb Mo Tc Ru Rh Pd Ag Cd La* Hf Ta W Re Os Ir Pt Au Hg Ac† Unq Unp Unh Uns Uno Une Uun Uuu f-block transition elements *Lanthanides Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu † Actinides Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
  5. 5. 20_435 0.2 La 1st series (3d) Y 2nd series (4d) Hf 3rd series (5d)Atomic radii (nm) Zr Sc Ta Au Nb W Ag 0.15 Re Mo Os Pt Ti Tc Ru Ir V Rh Pd Cr Fe Cu Mn Co Ni 0.1 Atomic number
  6. 6. Multiple Oxidation States
  7. 7. Metallic Behavior/Reducing Strength Lower oxidation state = more metallic
  8. 8. Color and Magnetisme- in partially filled d sublevel absorbs visible light moves to slightly higher energy d orbital Magnetic properties due to unpaired electrons
  9. 9. Electronegativity increases down column
  10. 10. ChromiumChemical properties reflect oxidation state
  11. 11. Valence-State ElectronegativityElectronegativity, EN: electron “pulling power”Valence-state EN: metal in higher oxidation state is more positive has stronger pull on electrons is more electronegative “Effective EN”
  12. 12. Manganese
  13. 13. Silver
  14. 14. Weak Reducing Agent, H2Q
  15. 15. Mercury
  16. 16. Coordination CompoundConsist of a complex ion and necessary counter ions [Co(NH3)5Cl]Cl2Complex ion: [Co(NH3)5Cl]2+ Co3+ + 5 NH3 + Cl- = 1(3+) + 5 (0) + 1(1-) = 2+Counter ions: 2 Cl-
  17. 17. [Co(NH3)6]Cl3 [Pt(NH3)4]Br2Complex ion remains intact upon dissolution in water
  18. 18. Complex IonSpecies where transition metal ion is surrounded by a certain number of ligands. Transition metal ion: Lewis acid Ligands: Lewis bases Co(NH3)63+ Pt(NH3)3Br+
  19. 19. LigandsMolecule or ion having a lone electron pair that can be used to form a bond to a metal ion (Lewis base).coordinate covalent bond: metal-ligand bond monodentate: one bond to metal ion bidentate: two bond to metal ion polydentate: more than two bonds to a metal ion possible
  20. 20. Formulas of Coordination Compounds1. Cation then anion2. Total charges must balance to zero3. Complex ion in brackets K2[Co(NH3)2Cl4] [Co(NH3)4Cl2]Cl
  21. 21. Names of Coordination Compounds1. Cation then anion2. Ligands in alphabetical order before metal ion neutral: molecule name* anionic: -ide → -o prefix indicates number of each3. Oxidation state of metal ion in () only if more than one possible4. If complex ion = anion, metal ending → -ate
  22. 22. ExamplesK2[Co(NH3)2Cl4] potassium diamminetetrachlorocobaltate(II)[Co(NH3)4Cl2]Cl tetraamminedichlorocobalt(III) chloride
  23. 23. 20_441 Isomers (same formula but different properties) Structural Stereoisomers isomers (same bonds, different (different bonds) spatial arrangements) Geometric Coordination Linkage Optical (cis-trans) isomerism isomerism isomerism isomerism
  24. 24. Structural Isomerism 1Coordination isomerism: Composition of the complex ion varies. [Cr(NH3)5SO4]Br and [Cr(NH3)5Br]SO4
  25. 25. Structural Isomerism 2Ligand isomerism: Same complex ion structure but point of attachment of at least one of the ligands differs. [Co(NH3)4(NO2)Cl]Cl and [Co(NH3)4(ONO)Cl]Cl
  26. 26. Linkage Isomers[Co(NH3)5(NO2)]Cl2 [Co(NH3)5(ONO)]Cl2Pentaamminenitrocobalt(III) Pentaamminenitritocobalt(III) chloride chloride
  27. 27. Stereoisomerism 1Geometric isomerism (cis-trans): Atoms or groups arranged differently spatially relative to metal ion Pt(NH3)2Cl2
  28. 28. 20_444 Cl Cl H3N NH 3 H3N NH3 Co Co H3N NH 3 H3N Cl Cl NH 3 Cl Cl Co Co Cl Cl (a) (b)
  29. 29. Stereoisomerism 2 Optical isomerism:20_446 Have opposite effects on plane-polarized light (no superimposable mirror images) Polarizing filter Tube containing Unpolarized sample light θ Polarized light Rotated polarized light
  30. 30. 20_448 Mirror image of right hand Left hand Right hand
  31. 31. 20_449 N N N Mirror image Co N N of Isomer I N N N N N N N Co Co N N N N Isomer I Isomer II N N
  32. 32. 20_450 Cl The trans isomer and Cl Isomer II cannot be its mirror image are superimposed exactly N N identical. They are not N N on isomer I. They are Co isomers of each other. Co not identical structures. N N N Cl Cl Cl Cl Cl N N N N Cl N Ntrans Co cis Co Co N N N N N Cl Cl Isomer I N Isomer II N Isomer II has the same structure as the mirror (a) (b) image of isomer I.
  33. 33. Crystal Field TheoryFocus: energies of the d orbitalsAssumptions1. Ligands: negative point charges2. Metal-ligand bonding: entirely ionicstrong-field (low-spin): large splitting of d orbitalsweak-field (high-spin): small splitting of d orbitals
  34. 34. 20_454 eg(d z2, d x 2 – y2) ∆ t2g (d xz, d yz, d xy) E ∆ = crystal field splitting Free metal ion 3d orbital energies
  35. 35. High spin Low spin
  36. 36. [V(H2O)6]2+ [V(H2O)6]3+[Cr(NH3)6]3+ [Cr(NH3)5Cl]2+s
  37. 37. 20_459 Tetrahedral Complexes – dz 2 dx2 – y2 – – – –– – – – – dxy dxz dyz (a) (b)
  38. 38. 20_461 Square Planar & Linear Complexes dx2 - y2 dz2 E E dxy dxz dyz dz2 dxy dx2 - y2 dxz dyz Free metal ion Complex Free metal ion Complex x M M z y (a) (b)Approach along x-and y-axes Approach along z-axis
  39. 39. Hemoglobin & Oxyhemoglobin