CH24 Naming

CH24: Complex Ions & Coordination Numbers

Tetrahedral and square planar complexes have a coordination number of

four

Trigonal bipyramidal and square pyramidal complexes have a coordination number of

five

Octahedral complexes have a coordination number of

six

Primary Valence

• apart of Werner’s theory

Based on the number of e- an atom loses in forming the ion.

• has the oxidation state that corresponds to the positive charge on the metal ion

Coordination Number

• apart of Werner’s theory

Responsible for the bonding of other groups, ligands, to the central metal atom

• Coordination number that is the total number of ligand-metal bonds bound to the metal ion

Relating the Formula of a Complex to the Coordination Number and Oxidation State of the Central Metal.

What are the coordination number and oxidation state of Co in the complex ion [CoCl(NO2)(NH3)4]+?

Complex has as ligands…1 Cl, 1 NO2, 4 NH3

Coordination Number: 6

Monodentate ligands

Use one pair of electrons to form one point of attachment to the metal ion

H2O as ligand (neutral)

aqua

NH3 as ligand (neutral)

ammine

CO as ligand (neutral)

carbonyl

NO as ligand (neutral)

nitrosyl

CH3NH2 as ligand (neutral)

methylamine

C5H5N as ligand (neutral)

pyridine

F- as ligand

fluoro

Cl- as ligand

chloro

Br- as ligand

bromo

I- as ligand

Iodo

O²- as ligand

oxo

OH- as ligand

hydroxo

CN- as ligand

cyano

Some common polydentate ligands (Chelating Agents)

en (ethylenediamine), ox²- (oxalato), & EDTA^4-

Rules of Complex Ion Nomenclature (naming)

1. Name the ligands first, in alphabetical order, followed by the name of the metal center.

2. oxidation state of the metal centre is given by a Roman numeral

3. If the complex is an anion the ending –ate is attached to the name of the metal

4. In names and formulas of coordination compounds, cations come first, followed by anions

Anions as ligands are named by using the ending –o…

Normally

• – ide endings change to –o.

• – ite endings change to –ito.

• – ate endings change to –ato

The number of ligands present in the complex is indicated with the prefixes di, tri, etc.

Exceptions are….

polydentates that have a prefix already in their name(en and EDTA4- are the most common)

When indicating how many of these are present in a coordination complex, put the ligand's name in parentheses and use bis, tris, or tetrakis

use bis, tris, or tetrakis

For polydentate ligands, when using prefixes to indicate # of ligands in order:

bis (2), tris (3), tetrakis (4), pentakis (5), hexkis (6)

Rules of Complex Ion Nomenclature (formula)

• when writing the formula

1. the chemical symbol of the metal is written first, followed by the formulas of anions (alphabetical)

2. then formulas of neutral molecules (alphabetical)

3. Use brackets to enclose the ion [not always required]

4. The charge of the ion is written outside of the bracket

For a complex ion containing only one type of ligand:

there is no problem

Ex) [Cu(H2O)6]²+

hexaaquacopper(II) ion

With more than one type of ligand in an ion, the ligands are

named in alphabetical order

[Cu(NH3)4(H2O)2]²+

• Note: tetra- & di- are ignored

tetraamminediaquacopper(II) ion