1. Complex Ions and Coordination Compounds
    PURDUE has a wonderful WEBSITE to teach you this stuff.
    GO THERE LEARN THE STUFF!!!!
    Be sure to look on the left of this page for more topics.
    1. A complex ion consists of a central metal cation (usually derived from a transition metal) joined by coordinate covalent bonds to two or more molecules or anions called ligands.

    Complex ion

    Cation

    Ligands

    Coordination no. (# of bonds)

    Ag(NH3)2+

    Ag+

    2 NH3 molecules

    2

    Cu(H2O)42+

    Cu2+

    4 H2O molecules

    4

    Fe(CN)63-

    Fe3+

    6 CN- ions

    6

    Coordination compound contains complex ion. Examples:

    [Cu(H2O)4]SO4 , [Ag(NH3)2]NO3, K3[Fe(CN)6]

    Usually Colored Compounds, SEE OH#2

    Charge of central metal atom in Zn(H2O) 3(OH)+ ?

    +1 = -1 + x; x = +2

     

    Do Cu
  1. Nature of ligands; ordinarily contain at least one unshared pair of electrons.

Note: Ligands are Lewis Bases, Metals are Lewis Acids…Look Up Why.

If the ligand contains two or more unshared pairs on different, nonadjacent atoms, it can act as a chelating agent, forming more than one bond with the central metal atom.

Forms bidentate complexes such as Co (en)33+  
SEE OH#3

  1. Nomenclatures: see rules P. 553
    1. Cation Co(NH3)4Cl+2

      2. You have four rules- Do it, name me!

      Tetraamminedichloro cobalt (II)

      Do it, name me! Ni(en)32+

      Tris(Ethylenediamine) Nickel (II)

    2. Anions® Put "Ate" after metal, name the rest same.

      3. Do it, name me! Al(OH)4-

      Tetrahydroxoaluminate (II)

      Write the formula for Pentachlorohydroxoferrate (III)

    3. Compounds ® just like ionic compounds. Above 2 with K+

[See notes for today- Go over lab Co Comp.]

  1. Geometry of Complex Ions
    1. Coordination no. = 2; linear

180° bond angle

Name these! Last chapter’s lab
     

    1. Coordination number = 4
    1. Tetrahedral: Zn(NH3)42+

(Last Chapter’s lab) CoCl42-

 

2. Square planar: Cu(H2O)42+

Can show isomerism:
             

cis isomer 
(like groups close)
polar 

trans isomer
 (like groups far apart)
nonpolar

 

  1. Geometry of Complex Ions
    1. Coordination number = 6; octahedral

All ligands same distance from metal atom.

Any position is trans to one position and cis to four others.

See fig 16.5

Co(NH3)4Cl2+ two isomers à see Fig 16.6, &. 7 note names

Co(NH3)3Cl3 two isomers à see Fig 16.8

                                                                            
        facial triamminetrichlorocobalt (III)                          ?

See 16.9 figure


II. Electronic Structure (Valence bond model) See p. 560 READ IT!

Electron pairs contributed by ligands enter hybrid orbitals of central metal ion.

  1. Orbitals occupied by ligand pairs

    2. Coord. No. = 2 sp

    Coord. No. = 4 sp3 (tetrahedral) or dsp2 (square planar)

    Coord. No. = 6 d2sp3(inner) or sp3d2(outer) see p.561 
    table 16.4 see OH #7

  2. Procedure: apply to Ni(CN)42-, Cr(H20)63+ (2 examples)

Put a line down the center of your page [follow page 562 the rules]

1. Determine electron configuration of central metal.

(no s electrons)

Ni2+ 3d8                 Cr3+ 3d3

2. Determine coordination number: 4, 6

3. Decide upon hybridization: dsp2

see p 562 rule "a" to find it is

d2sp3

4. Locate electron pairs in hybrid orbitals

5. Distribute electrons of metal in accordance with Hund’s rule.


Bottom one is paramagnetic

III. Equilibria Involved in Complex Ion Formation

  1. Formation constants

    2. Ag+(aq) + 2NH3(aq) ß > Ag(NH3)2+(aq); Kf = 2 x 107

    Ag+(aq) + 2CN-(aq) ß > Ag(CN)2-(aq); Kf = 1 x 1021

    Ag(CN)2- more stable than Ag(NH3)2+ see OH #11

  2. Application: Calculate ratio of [Ag+]/[Ag(NH3)2+] in 0.1 M NH3

This shows most of the silver is complexed.

Coordination #

Choices

How to Choose

Hybridization

Geometry

2

sp

--------

sp

Linear

4

sp3, dsp2

Told geometry or hybridization

sp3

tetrahedral

Told geometry or hybridization

dsp2

square planar

6

d2sp3, sp3d2

d0-d3

d2sp3

octahedral

d4-d7 low spin

d2sp3

octahedral

d4-d7 high spin

sp3d2

octahedral

d8-d10

sp3d2

octahedral

 

 

For the test you should be able to do this type of problem:

Co (en) Cl4- (high spin)

  1. Name this ion.

    2. Using V.B. Model Deduce

  2. The electron configuration.
  3. The coordination #.
  4. The hybridization.
  5. Draw the orbital diagram.
  6. Show Geometric isomers! Draw them, if any.
    7.

 

¬ tetrachloroethylenediaminecobaltate (III)

­ [Ar] 3d6

® Coordination # = 6

¯ sp3d2

        3d                           4s                   4p

° (­¯)(­  )(­  )(­ )(­ )        (­¯)        (­¯)(­¯)(­¯)

                     4d

    (­¯)(­¯)(     )(      )(     )

±

 

 

 

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Lee Marek