Chapter 23: The Transition Elements and
Their Coordination Compounds
23.1 An Overview of Transition Element Properties
23.2 The Inner Transition Elements
23.3 Highlights of Selected Transition Metals
23.4 Coordination Compounds
23.5 Theoretical Basis for the Bonding and Properties of Complexes
Fig. 23.1
Orbital Occupancy of the Period 4 Metals–I
Element
Sc
Partial Orbital Diagram
4s
3d
Unpaired Electrons
4p
1
Ti
2
V
3
Cr
6
Mn
5
Table 23.1 (p. 1003)
Orbital Occupancy of the Period 4 Metals–II
Element
Fe
Partial Orbital Diagram
4s
3d
Unpaired Electrons
4p
4
Co
3
Ni
2
Cu
1
Zn
0
Table 23.1 (p. 1003)
Fig. 23.3
Fig. 23.4
Aqueous Oxoanions of V, Cr, and Mn in their
Highest Oxidation States
Fig 23.5
Oxidation States and d-Orbital Occupancy of the
Period 4 Transition Metals
Oxidation
State
0
3B
(3)
Sc
4B
(4)
Ti
0
(d1)
0
(d2)
+1
+2
+3
+4
+5
+6
+7
+3
(d0)
5B
(5)
V
6B
(6)
Cr
0
0
(d3) (d5)
+1 +1
(d3) (d5)
+2
+2
+2
(d2) (d3) (d4)
+3
+3
+3
(d1) (d2) (d3)
+4
+4
+4
(d0) (d1) (d2)
+5
+5
(d0) (d1)
+6
(d0)
7B
(7)
Mn
8B
(8)
Fe
8B
(9)
Co
0
0
0
(d5) (d6) (d7)
+1
+1
(d5)
(d7)
+2
+2
+2
(d5) (d6) (d7)
+3
+3 +3
(d4) (d5) (d6)
+4
+4
+4
(d3) (d4 ) (d5)
+5
+5
(d2)
(d4)
+6
+6
(d1) (d2)
+7 (d0)
8B
(10)
Ni
1B
(11)
Cu
2B
(12)
Zn
0
0
0
(d 8) (d10) (d10)
+1
+1
(d8) (d10)
+2
+2
+2
(d8) (d9) (d10)
+3
+3
(d7) (d8)
+4
(d6)
Table 23.2
(p. 1006)
Standard Electrode Potentials of
Period 4 M2+ Ions
E0 (V)
Half-Reaction
Ti2+(aq) + 2 eV2+(aq) + 2 eCr2+(aq) + 2 eMn2+(aq) + 2 eFe2+(aq) + 2 eCo2+(aq) + 2 eNi2+(aq) + 2 eCu2+(aq) + 2 eZn2+(aq) + 2 e-
Table 23.3 (p. 1007)
Ti(s)
V(s)
Cr(s)
Mn(s)
Fe(s)
Co(s)
Ni(s)
Cu(s)
Zn(s)
-1.63
-1.19
-0.91
-1.18
-0.44
-0.28
-0.25
0.34
-0.76
Colors of Representative Compounds of
the Period 4 Transition Metals
b
a
d
c
f
e
h
g
j
i
a = Scandium oxide
f = Potassium ferricyanide
b = Titanium(IV) oxide
g = Cobalt(II) chloride hexahydrate
c = Vanadyl sulfate dihydrate
h = Nickel(II) nitrate hexahydrate
d = Sodium chromate
i = Copper(II) sulfate pentahydrate
e = Manganese(II) chloride tetrahydrate j = Zinc sulfate heptahydrate
Fig. 23.6
(p. 1012)
Coordination Compounds: Complexes
• Lewis acids are electron pair acceptors.
• Coordination compounds are metal compounds
formed by Lewis acid-base interactions.
• Complexes: Have a metal ion (can be zero
oxidation state) bonded to a number of ligands.
Complex ions are charged. Example,
[Ag(NH3)2]+.
• Ligands are Lewis bases.
• Coordination number: the number of ligands
attached to the metal.
Coordination Numbers and Geometry
• The most common coordination numbers are 4 and 6.
• Some metal ions have a constant coordination number
(e.g. Cr3+ and Co3+ have a coordination number of 6).
• The size of the ligand affects the coordination number
(e.g. [FeF6]3- forms but only [FeCl4]- is stable).
• The amount of charge transferred from ligand to metal
affects coordination number (e.g. [Ni(NH3)6]2+ is stable
but only [Ni(CN)4]2- is stable).
• Four coordinate complexes are either tetrahedral or
square planar (commonly seen for d 8 metal ions).
• Six coordinate complexes are octahedral.
(Square brackets enclose the metal ion and ligands.)
Fig. 23.9
(p. 1017)
Ligands
• Monodentate ligands bind through one donor
atom only.
– Therefore they occupy only one coordination site.
• Polydentate ligands (or chelating agents) bind
through more than one donor atom per ligand.
– Example, ethylenediamine (en), H2NCH2CH2NH2.
• The octahedral [Co(en)3]3+ is a typical en
complex.
• Chelate effect: More stable complexes are formed
with chelating agents than with the equivalent
number of monodentate ligands.
(p. 1018)
Nomenclature
• Rules:
– For salts, name the cation before the anion. Example
in [Co(NH3)5Cl]Cl2 we name [Co(NH3)5Cl]2+ before
Cl-.
– Within a complex ion, the ligands are named (in
alphabetical order) before the metal.
Example
[Co(NH3)5Cl]2+ is tetraamminechlorocobalt(II). Note
the tetra portion is an indication of the number of NH3
groups and is therefore not considered in the
alphabetizing of the ligands.
– Anionic ligands end in -o and neutral ligands are
simply the name of the molecule. Exceptions: H2O
(aqua) and NH3 (ammine).
Nomenclature
• Rules:
– Greek prefixes are used to indicate number of ligands
(di-, tri-, tetra-, penta-, and hexa-). Exception: if the
ligand name has a Greek prefix already. Then enclose
the ligand name in parentheses and use bis-, tris-,
tetrakis-, pentakis-, and hexakis.
• Example [Co(en)3]Cl3 is tris(ethylenediamine)cobalt(III)
chloride.
– If the complex is an anion, the name ends in -ate.
– Oxidation state of the metal is given in Roman
numerals in parenthesis at the end of the complex
name.
Names of Some Neutral and Anionic Ligands
Name
A. Neutral
Aqua
Ammine
Carbonyl
Nitrosyl
B. Anionic
Fluoro
Chloro
Bromo
Iodo
Hydroxo
Cyano
Table 23.8 (p. 1019)
Formula
H2O
NH3
CO
NO
FClBrIOHCN-
Names of Some Metal Ions in Complex Anions
Metal
Name in Anion
Iron
Ferrate
Copper
Cuprate
Lead
Plumbate
Silver
Argentate
Gold
Aurate
Tin
Stannate
Table 23.9 (p. 1019)
Some Coordination Compounds of Cobalt
Studied by Werner
Werner’s Data*
Total Free
Ions
Cl-
Traditional
Formula
.
CoCl . 5 NH
CoCl . 4 NH
CoCl . 3 NH
CoCl3 6 NH3
Modern
Formula
Charge of
Complex Ion
4
3
[Co(NH3)6]Cl3
3+
3
3
3
2
[Co(NH3)5Cl]Cl2
2+
3
3
2
1
[Co(NH3)4Cl2]Cl
1+
3
3
0
0
[Co(NH3)3Cl3]
---
Table 23.10 (p. 1020)