Unless otherwise stated, all images in this file have been reproduced from:

Blackman, Bottle, Schmid, Mocerino and Wille,     Chemistry, 2007 (John Wiley)

     ISBN: 9 78047081 0866

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e CHEM1002 [Part 2]

A/Prof Adam Bridgeman (Series 1)Dr Feike Dijkstra (Series 2)

Weeks 8 – 13

Office Hours: Monday 2-3, Friday 1-2Room: 543ae-mail: adam.bridgeman@sydney.edu.aue-mail: feike.dijkstra@sydney.edu.au

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e

Complexes I

• Solutions of metal ions are acidic because coordinated water loses H+ and this increases with the charge of the metal ion

• Ligands use lone pairs to bond to transition metal ions• Coordination compounds are made up of a complex ion,

containing a metal ion and ligands, and counter ions to balance the charge

• The common geometries of complex ions are tetrahedral and square planar (both 4 coordinate) and octahedral (6 coordinate)

Summary of Last Lecture

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e

Lecture 13• Isomerism• Stability• Blackman Chapter 13, Sections 13.1-13.4

Lecture 14• Transition Metals• Electron Configuration• Oxidation States• Colours• Magnetism• Blackman Chapter 13, Sections 13.4 and 13.7

Complexes II

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e Isomerism in Metal Complexes (1)

• Structural Isomerism: different atom connectivities If the counter ions are also potential ligands, they can

swap places to produce coordination sphere isomers:

[Cr(OH2)4Br2]Cl [Cr(OH2)4BrCl]Br

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e

H3NPt

Cl

Cl

H3N

ClPt

Cl

NH3

H3N

cis trans

Isomerism in Metal Complexes (2)

• Stereoisomerism: same atom connectivities but different arrangement of atoms in space geometric isomerism

cis trans

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e

mirror imagessuperposable(i.e. the same!)

mirror imagesnon-superposable

mirror imageOPTICALLY

ACTIVE

NiN N

NNOH2

OH2

2+

NiN N

NNOH2

OH2

2+

2+

NiH2O N

NH2ON

N

NiN OH2

OH2NN

N

2+

Isomerism in Metal Complexes

transisomer

cisisomer

• Stereoisomerism: same atom connectivities but different arrangement of atoms in space optical isomerism

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e Isomerism in Metal Complexes• Stereoisomerism: same atom connectivities but different

arrangement of atoms in space optical isomerism

[Ni(en)3]3+

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e Equilibria Involving Complexes

• Unlike the covalently bonded polyatomic ions such as NO3-,

SO42-, etc., which do not dissociate into their components,

metal complexes in solution are in an equilibrium:

[M(OH2)6]2+ + 6NH3 [M(NH3)6]2+ + 6H2O

[M(NH3)6]2+ + 3en [M(en)3]2+ + 6NH3

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e [Ni(H2O)6]2+ + 3en [Ni(en)3]2+ + 6H2O

Kstab =

Kstab = K1 K2 K3 = 1018.28

[Ni(en)2(H2O)2]2+ + en [Ni(en)3]2+ + 2H2Opurple

[Ni(en)(H2O)4]2+ + en [Ni(en)2(H2O)2]2+ + 2H2Olight blue

[Ni(H2O)6]2+ + en [Ni(en)(H2O)4]2+ + 2H2Ogreen blue-green

Stepwise Formation Constants

[[Ni(H2O)6]]2+][en]3

[[Ni(en)3]2+] = 1018.28

K2

K1

K3

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e

• Metal complex formation can greatly influence the apparent solubility of a compound.

AgCl(s) + 2NH3(aq) [Ag(NH3)2]+(aq) + Cl-(aq)

• This is actually a two stage process:

AgCl(s) Ag+(aq) + Cl-(aq) (1)

Ag+(aq) + 2NH3(aq) [Ag(NH3)2]+(aq) (2)

• Complex formation (reaction 2), removes free Ag+ from solution and so drives the dissolution of AgCl (reaction 1) forward.

Metal Complex Formation and Solubility

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i The One Pot Reaction

Ag+(aq) + OH-(aq) AgOH(s) brown AgOH(s) + H2PO4

-(aq) AgH2PO4(s) yellowAgH2PO4(s) + HNO3(aq) Ag+(aq) + H3PO4(aq)Ag+(aq) + Cl-(aq) AgCl(s) white Ksp = 1.8 x 10-10 M2

AgCl(s) + 2 NH3(aq) [Ag(NH3)2]+(aq) + Cl-(aq) Kstab = 1.7 x 107 M-2

[Ag(NH3)2]+(aq) + Br-(aq) AgBr(s) (green/white), Ksp = 5 x 10-13 M2

AgBr(s) + 2 S2O32-(aq) [Ag(S2O3)2]3-(aq)+Br-(aq) Kstab = 2.5 x 1013 M-2

[Ag(S2O3)2]3-(aq) + I-(aq) AgI(s) (yellow) Ksp = 8.3 x 10-17 M2

AgI(s) + 2 CN-(aq) [Ag(CN)2]-(aq) + I-(aq) Kstab = 6.3 x 1019 M-

2 [Ag(CN)2]-(aq) + S2-(aq) Ag2S(s) (black) Ksp = 8 x 10-51 M3

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e Summary: Complexes IILearning Outcomes - you should now be able to:

• Complete the worksheet• Identify isomers of complexes correctly• Answer review problems 13.59-13.62 in Blackman

Next lecture:

• Colour

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x Practice Examples1. What are the possible geometries of a metal complex with a

coordination number of 4?

A.square planar or tetrahedral or octahedralB.square planar or tetrahedralC.octahedral onlyD.tetrahedral onlyE.square planar only

2. Which one of the following is a coordination isomer of the complex salt,

trans- [Cr(H2O)4Cl2]Br?

A.cis- [Cr(H2O)4Cl2]BrB.trans- [Cr(H2O)4BrCl]ClC.trans- [Cr(H2O)4Br2]ClD.trans- [CrBr2(H2O)4]ClE.trans- [CrCl2(H2O)4]Br

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x Practice Examples3. Which of the following species exist as isomers?

[Co(NH3)6]3+, [PtCl2(NH3)2], [Co(OH2)6]Cl3, [Co(OH2)6]2+, [CdI4]2–

A.[PtCl2(NH3)2] and [Co(OH2)6]Cl3B.[PtCl2(NH3)2] onlyC.[CdI4]2– onlyD.[Co(NH3)6]3+ and [Co(OH2)6]2+

E.[Co(OH2)6]Cl3 and [Co(OH2)6]2+

4. How many geometrical isomers are possible for the complex [CrCl3(NH3)3]?

A.1B.2C.3D.4E.6