Starter

1) Electronic configuration of:a) Sc3+

b) Fe2+

c) Cu+

2) Suggest and explain the colour of compounds containing Zn2+

Transition metals and complex ions

L.O.:Explain the term ligand in terms of coordinate bonding.

Describe and use the terms: complex ion and coordination number.

State and give examples of complexes with six-fold coordination with an octahedral shape.

Complex ion [Fe(H2O)6]2+

Complex ions - Definations

• LIGAND – molecule or ion that can donate a pair of electrons to form a coordinate or dative covalent bond

• COORDINATE BOND – a bond where both electrons are provided for by the same atom. It is the same as a dative covalent bond but involves transition metals instead.

• COMPLEX ION – A transition metal ion bonded to one or more ligands by coordinate bonds (dative covalent bonds)

Coordination number

• This is the number of coordinate bonds are attached to the central metal ion

E.g. [Fe(H2O)6 ]2+

The overall charge of this complex is the sum of the metal charges and the charges on the ions that it is coordinated to

Calculate the oxidation number of the metal in:

a)[Cu(NH3)(H2O)]2+

b)[Co(H2O)5Cl]+

Cobalt complex containing 6 monodentate ligands

• Notice the shape adopted by this complex, what is it and what are the bond angles?

[Co(H2O)6]2+ is an octahedral complex ion

L.O.:

Describe stereoisomerism in transition metal complexes using examples of cis–trans and optical isomerism.

Describe the use of cis–platin as an anti-cancer drug, and its action by binding to DNA.

Cis–trans isomerism in [Co(NH3)4Cl2]+

Cis–trans isomerism in [NiCl2(NH3)2]

Structure of cis-platin

L.O.:Explain and use the term: bidentate ligand

(e.g. NH2CH2CH2NH2, ‘en’).

Describe stereoisomerism in transition element multidentate complexes using examples of cis–trans and optical isomerism.

Structure of the ethanedioate ligand, C2O42–

Bidentate: it can donate two lone pairs of electrons to the central metal ion to form two coordianate bonds

More bidentate ligands:

ethane-1,2-diamine, NH2CH2CH2NH2

Complex ion [Ni(en)3]2+

Cis–trans isomerism in [Co(NH3)4Cl2]+

Cis and trans isomers of [Cr(C2O4)2(H2O)2]–

Structure of cis-platin

Optical isomers of [Ni(NH2CH2CH2NH2)3]2+

Optical isomerism

Necessary conditions for optical isomerism

Complexes must have either:3 bidentate ligands, e.g. [Ni(en)3 ]2+

2 bidentate and 2 monodentate ligands, e.g. [Co(en)2 Cl2 ]

1 hexadentate ligand – e.g. [Cu(EDTA)]2-

Drawing optical isomers

• First draw the bonds around the metal ion• Then add the ligands to the first complex• Then complete the second complex as a

mirror image of the first