Transition Metals & Complex ions

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

• Describe and use the terms: Describe and use the terms: complex ioncomplex ion and and coordination numbercoordination number..

• Explain the term Explain the term ligandligand in terms of coordinate in terms of coordinate bonding.bonding.

Definition Hangman – Coordinate bond Definition Hangman – Coordinate bond (aka – dative covalent bond)(aka – dative covalent bond)

_ / _ _ _ _ _ _ / _ _ _ _ / _ _ / _ _ _ _ _ _ _ _ _

/ _ _ / _ _ _ _ _ / _ _ _ / _ _ _ _ _ _ / _ _ _ _ /

_ _ _ / _ _ _ _ / _ _ _ _ _ _ _ _ / _ _ / _ _ _ /

_ _ / _ _ _ / _ _ _ _ _ _ _ / _ _ _ _ _ / _ _ _ _.

A shared pair of electrons in which

the bonded pair has been provided

by one of the bonding atoms only.

Complex ion [Fe(HComplex ion [Fe(H22O)O)66]]2+ 2+

Each of the six H2O ligands forms one coordinate (dative

covalent) bond to the central metal ion

using a lone pair of electrons from its

oxygen atom.

This complex ion has a coordination number of six (the number of coordinate bonds to the central metal ion)

Charges on complex ionsCharges on complex ions

Name of ligand

Formula Charge

Water :OH2 None - neutral

Ammonia :NH3 None - neutral

Thiocyanate :SCN- -1Cyanide :CN- -1Chloride :Cl- -1

Hydroxide :OH- -1

The overall charge of a complex ion is the sum of the individual charges of the transition metal ion and those of the ligands.

ExampleState the formula and charge of the complex ion made from one Iron (II) ion and 6 cyanide molecules.

[Fe(CN)6]4-

All of these ligands are classed as monodentate ligands (i.e. They only donate one pair of electrons to the central metal ion)

Formulae QuestionsFormulae Questions1. State the formula & charge of each of these complex ions:

a) One copper (II) ion & four chloride ionsb) One iron (III) ion & five water molecules & a chloride ion.c) One copper (II) ion & four ammonia molecules & two hydroxide

ionsd) One cobalt (III) ion & four hydroxide ions

2. What is the oxidation number of the transition metal in each of these complex ions.

a) [Fe(CN)6]3-

b) [Co(SCN)4]2-

c) [Cu(CN)4(Cl)2]4-

d) [Ti(H2O)3OH]2+

3D shapes of complex ions3D shapes of complex ions

Most common shape = octahedral ( 6 coordinate bonds)BOND ANGLE = all 90BOND ANGLE = all 90oo

3D shapes of complex ions3D shapes of complex ions

Less common shape = tetrahedral ( 4 coordinate bonds)

BOND ANGLE = all 109.5BOND ANGLE = all 109.5oo

The copper(II) and cobalt(II) ions have four chloride ions

bonded to them rather than six,

because the chloride ions are too big to fit any more around the central metal ion.

Shapes of complex ions QuestionsShapes of complex ions Questions

For each of the 8 complex ions you worked with during “formulae questions” draw the 3D shape using the wedge shaped bonds, show the bond angles and name the shape.

Reminder – what is a Reminder – what is a stereoisomer?stereoisomer?

• Molecules or complexes with the same structural formula but with a different arrangement of the atoms in space.

Stereoisomerism in complex ions Stereoisomerism in complex ions Cis–trans isomerism in [Co(NH3)4Cl2]+

Chloride ligands at 90o to each other

Chloride ligands at

180o to each other

Stereoisomerism in complex ions Stereoisomerism in complex ions Cis–trans isomerism in [NiCl2(NH3)2]

4 coordinate bonds – alternative to tetrahedral = Square Planar

BOND ANGLE = all 90BOND ANGLE = all 90oo

Structure of cis-platin

Effective cancer treatment –

Thought to bind to and alter cancer cell DNA and therefore

prevent their growth and reproduction

1. What is the formula for cis-platin?2. Explain why this molecule uses the prefix “cis” in its name.