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					Transition Metals and Coordination
            Chemistry

            Chapter 23
               Transition Metals


Similarities within a given period
     and within a given group.

Last electrons added are inner electrons (d’s, f’s).
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
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 elemen ts

         *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
20_435




                    0.2
                               La
                                                                              1st series (3d)
                           Y                                                  2nd series (4 d)
                                         Hf                                   3rd series (5d)
Atomic radii (nm)




                                         Zr
                           Sc                 Ta
                                                                                          Au
                    0.15                      Nb   W                                      Ag
                                                   Mo       Re     Os
                                    Ti                      Tc           Ir        Pt
                                                                   Ru
                                              V                          Rh        Pd
                                                   Cr               Fe                     Cu
                                                            Mn           Co       Ni


                     0.1
                                                        Atomic number
Multiple Oxidation States
Metallic Behavior/Reducing Strength
    Lower oxidation state = more metallic
           Color and Magnetism


e- in partially filled d sublevel absorbs visible light
   moves to slightly higher energy d orbital




      Magnetic properties due to unpaired electrons
Electronegativity increases down column
            Chromium
Chemical properties reflect oxidation state
      Valence-State Electronegativity
Electronegativity, 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”
Manganese
Silver
Weak Reducing Agent, H2Q
Mercury
            Coordination Compound
Consist of a complex ion and necessary counter ions
     [Co(NH3)5Cl]Cl2

Complex ion:    [Co(NH3)5Cl]2+
                     Co3+ + 5 NH3 + Cl-
                  = 1(3+) + 5 (0) + 1(1-)
                  = 2+

Counter ions:   2 Cl-
      [Co(NH3)6]Cl3                     [Pt(NH3)4]Br2




Complex ion remains intact upon dissolution in water
                 Complex Ion
Species 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+
                    Ligands
Molecule 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
   Formulas of Coordination Compounds

1.Cation then anion
2.Total charges must balance to zero
3.Complex ion in brackets

                K2[Co(NH3)2Cl4]

                [Co(NH3)4Cl2]Cl
    Names of Coordination Compounds
1.Cation then anion
2.Ligands
     in alphabetical order before metal ion
            neutral:     molecule name*
            anionic:     -ide  -o
     prefix indicates number of each
3.Oxidation state of metal ion in () only if more
  than one possible

4.If complex ion = anion, metal ending  -ate
                  Examples
K2[Co(NH3)2Cl4]
 potassium diamminetetrachlorocobaltate(II)

[Co(NH3)4Cl2]Cl
 tetraamminedichlorocobalt(III) chloride
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
           Structural Isomerism 1

Coordination isomerism:
 Composition of the complex ion varies.


               [Cr(NH3)5SO4]Br
          and [Cr(NH3)5Br]SO4
            Structural Isomerism 2

Ligand 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
                   Linkage Isomers




[Co(NH3)5(NO2)]Cl2            [Co(NH3)5(ONO)]Cl2
Pentaamminenitrocobalt(III)   Pentaamminenitritocobalt(III)
      chloride                      chloride
              Stereoisomerism 1
Geometric isomerism (cis-trans):

  Atoms or groups arranged differently spatially
  relative to metal ion

                   Pt(NH3)2Cl2
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)
                     Stereoisomerism 2
 Optical isomerism:
20_446


         Have opposite effects on plane-polarized light
         (no superimposable mirror images)
                           Polarizing
                           filter


                                         Tube
                                         containing
 Unpolarized
                                         sample
 light                                                      
                         Polarized
                         light

                                          Rotated
                                          polarized light
20_448




                                  Mirror image
                                  of right hand
         Left hand
                     Right hand
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
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          N
trans        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.
              Crystal Field Theory
Focus:      energies of the d orbitals

Assumptions
1.Ligands:                   negative point charges
2.Metal-ligand bonding:      entirely ionic

strong-field (low-spin): large splitting of d orbitals
weak-field (high-spin): small splitting of d orbitals
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
High spin   Low spin
[V(H2O)6]2+      [V(H2O)6]3+




[Cr(NH3)6]3+   [Cr(NH3)5Cl]2+s
20_459

                     Tetrahedral Complexes




                 –                    dz 2         dx2 – y2
   –                    –
                     – –– –
         –              –
             –


                                dxy          dxz              dyz
  (a)                         (b)
20_461

           Square Planar & Linear Complexes
                             dx2 - y 2
                                                                      dz2

                                         E
 E                          dxy                                 dxz         dyz
                            dz2
                                                                dxy     dx2 - y 2
                          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
Hemoglobin & Oxyhemoglobin

				
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posted:12/3/2011
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