25 Coordination Compounds

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25 Coordination Compounds Powered By Docstoc
					                Acids               Bases


Arrhenius    proton donor       hydroxide donor
                 H+                  OH-


Bronsted    proton donor        proton acceptor



 Lewis      electron pair (:)     electron pair (:)
              acceptor                donor
                bond formed
       H                        H
     H-N: + H+               H-N:H+
       H                        H
             H+
           H-N→H
             H
Coordinate covalent bond (dative bond)
one molecule provides both electrons (Lewis base)
the other molecule accepts electron pair
into an empty orbital (Lewis acid)
+1                                                      none
              Periodic Table
     +2           ion formation
                                             -3 -2 -1
H                                                       He
                                  +3
Li Mg                                    B C N O     F Ne
Na Mg     Transition metals - variable   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 Rf Db Sg Bh Hs Mt Ds


               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
             Transition Metals – Oxidation states
                             Table 25-1 on page 908


d1s2     d2s2     d3s2    d5s1     d5s2   d6s2    d7s2   d8s2     d10s1   d10s0
Sc      Ti        V       Cr      Mn Fe           Co     Ni       Cu Zn
+3 d0   +3 d1     +3 d2    0 d6   +1 d6 0 d8      0 d9    0 d10   +1 d10 +2 d10
        +4 d0     +5 d0   +2 d4   +2 d5 +2 d6    +1 d8   +2 d8    +2 d9
                          +3 d3   +3 d4 +3 d5    +2 d7
                          +4 d2   +5 d2          +3 d6
                          +6 d0   +7 d0

                Electronic Configuration review
                      Mn         [Ar] 4s2 3d5
                      Mn+1       [Ar] 3d6
                      Mn+2       [Ar] 3d5
                      Mn+5       [Ar] 3d2
Transition Metals – Coordination compounds

  Transition metals often have empty d orbitals

   The orbitals can act a Lewis acids

  They form coordinate covalent bonds with other molecules
  (ligands) which act as Lewis bases by donating a
  lone pair of electrons.
  Coordination compounds may have > octet and their
  geometry can be tetrahedral, trigonal bipyramidal,
  octahedral, etc.
  Coordination compounds often absorb light in visible
  range and thus have various colors
   Coordination compounds - example

       Hexaaquachromium (III) – complex ion

          HOH
                     [Cr(OH2)6]3+
           ..
H2O:                 :OH2
                3+

           Cr                As neutral compound
                              [Cr(OH2)6](NO3)3
H2O:                  :OH2
           ..
          HOH
Coordination compounds – Ligands
               (Table 25-4) on page 911
 monodentate (takes up one orbital place)
 ..
:OH2    aqua                        ..
                                  :Cl:
                                    ..     chloro
:NH3    ammine                      ..
                                   :F:
                                    ..     fluoro
:C≡O:   carbonyl

:PH3    phosphine                 :C≡N:-      cyano

                                   .. -
:N=O:
 . ..   nitrosyl                  :O-H
                                   ..        hydroxo

                     .. -
                     O: ..
                    :N=O: ..    nitro
    Polydentate Ligands -                  Table 25-5 on page 912


   ethylenediamine (en)                 bidentate
                 ..        ..
               H2N-CH2-CH2-NH2

diethylenetriamine (dien)                  tridentate
             ..       ..       ..
           H2N-(CH2)2-N-(CH2)2-NH2
                      H

Ethylenediamintetraacetato (edta)              hexadentate
       -OOC   – CH2                       CH2 – COO-
                      ..           ..
                      N – (CH2)2 - N
       -OOC   – CH2                       CH2 – COO-
            Nomenclature – page 913
1) Cation name 1st (leave a space) anion name

2) a) Ligands named in alphabetical order
   b) ligand prefixes
      mondentate – di, tri, tetra, penta, hexa (not in alphabet)
      (polydentate) – bis (2), tris (3), tetrakis (4) (not in alphabet)

3) Anionic ligands end in – o (chloro, nitro, hydroxo, etc.)
4) Neutral ligands names either unchanged or (table 25-4 p911)

5) Roman Numerals designate metal oxidation states (II).
6) -ate ending used for metals in complex anions (Table 25-6 – p913)
  K3[FeF6]                Cu(NH3)2(H2O)22+

 (NH4)2[Fe(H2O)F5]             K4[Mo(CN)8]

  CrF63-       Fe(CO)5         Rh(CN)2(en)2+

[Cr(NH3)4SO4]Cl

Potassium hexacyanomanganate(III)
sodium tetracyanozincate(II)

 tetraamminedichlorocobalt(III) nitrate

 hexaamminechromium(III) tetrachlorocuprate(II)
  Coordination compounds – geometry
                  Table 25-7 on page 914
Coordination #       geometry              example(s)

      2                 linear             [Cu(CN)2]-
      4              tetrahedral           [Zn(CN)4]2-

                    square planar          [Ni(CN)4]2-

      5          trigonal bipyramidal       Fe(CO)5

                  square pyramidal         [Ni(CN)5]3-

      6              octahedral            [Fe(CN)6]4-
  Isomers – same formula but different compounds.

    Cl               NH3      NH3            Cl

             Pt                       Pt
   Cl                NH3      Cl             NH3

         cis – pale yellow     trans – dark yellow


         diamminedichloroplatinum (II)
               square planar

Used in cancer chemotherapy
             Transition Metals – Oxidation states
                             Table 25-1 on page 908


d1s2     d2s2     d3s2    d5s1     d5s2   d6s2    d7s2   d8s2     d10s1   d10s0
Sc      Ti        V       Cr      Mn Fe           Co     Ni       Cu Zn
+3 d0   +3 d1     +3 d2    0 d6   +1 d6 0 d8      0 d9    0 d10   +1 d10 +2 d10
        +4 d0     +5 d0   +2 d4   +2 d5 +2 d6    +1 d8   +2 d8    +2 d9
                          +3 d3   +3 d4 +3 d5    +2 d7
                          +4 d2   +5 d2          +3 d6
                          +6 d0   +7 d0

                Electronic Configuration review
                      Mn         [Ar] 4s2 3d5
                      Mn+1       [Ar] 3d6
                      Mn+2       [Ar] 3d5
                      Mn+5       [Ar] 3d2
                    dxz                     dz2
                                        z
              z                                   y
                          y
                                                   x
                          x



    dxy, dxz, dyz electron density between axes
dz2 and dx2-y2 electron density located along x & y axes
t2g = dxy, dxz, dyz             eg = dz2 & dx2-y2
               z                    z
                       y                       y

                        x                       x



   dxy, dxz, dyz electron density between axes

        dz2 and dx2-y2 along x & y axes
               Crystal Field Theory
           A ligand is a Lewis base – electron pair donor

In transition metal atoms all 5 d orbitals have the same energy –
 They are called degenerate.

The ligands may approach central metal ion/atom along axes,
e.g octahedral, or between axes, e.g. tetrahedral.

These ligands will be repelled by the electrons occupying orbitals
along the direction in which they approach.
This is the concept of the crystal (electric) field.

The repulsion caused by Ligand fields overlapping the Metal
ion/atom field will raise the energy of the eg orbitals (octahedral)
or the energy of the t2g orbitals (tetrahedral).
                                                           metal ion/atom

             High spin P > Doct                                       eg

                                    eg                Low spin P < Doct
octahedral

                                          t2g                              t2g


  Weak field ligands – Doct is small
   example = F-                                      Splitting energy = Doct
                                                     Pairing energy = P
   Strong field ligands – Doct is large
    example = CN-
                                                [CoF6]3- vs. [Co(CN)6]3-
l
nm    10-3     10-1     100    103    105         107      109    1011    1013
m     10-12    10-10    10-9   10-6       10-4    10-2     100     102    104



      grays xrays UV                 IR           mwaves          radio

n    1020     1018     1016    1014       1012     1010     108    106    104
s-1 high energy                                            low energy

                                                    E = hn
                                                    J = Js  s-1
                     visible                     h = 6.626 x 10-34 Js
                   Spectrochemical Series
  Ligands influence the value of Doct by virtue of their crystal field strength.
  Strong field ligands produce larger splitting energy (Doct).


I- < Br- < Cl- < F- < OH- < H2O < (COO)22- < NH3 < en < NO2- < CN-

  High spin complexes >>>>>>>>>>>>>>>>>>>>>>> Low spin


      e.g. Ni2+ d8 octahedral complexes with ….

       H2O, bipyridine, en, NH3, glycine
Light         Violet   blue         green    yellow    orange       red

        400                   500                    600                  700




                                            Orange
                                             A450
  Color
                          Red                              Yellow
                          A500                              A400



                          Violet                           Green
                           A550                             A650

                                            Blue
                                            A600
[Ni(H2O)6]2+                [Ni(bipyr)3]2+                   [Ni(en)3]2+

               Ni(gly)3                       [Ni(NH3)6]2+
0.7
0.6
0.5
0.4
0.3
0.2
0.1
 0
  450         500          550          600         650      700

        H2O         teal         blue         lavender    red
 Weak field ligand
           l
eg                    eg


     t2g                   t2g



strong field ligand
eg         l          eg




     t2g                   t2g
+1                                                      none
              Periodic Table
     +2           ion formation
                                             -3 -2 -1
H                                                       He
                                  +3
Li Mg                                    B C N O     F Ne
Na Mg     Transition metals - variable   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 Rf Db Sg Bh Hs Mt Ds


               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
                   t2g
tetrahedral

              eg

				
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