Transition Metals and Coordination Chemistry

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Chapter 20

• Transition Metals and Coordination Chemistry

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Chapter 20 Transition Metals and
Coordination Chemistry
20.1 The Transition metals A Survey 20.2 The
First-Row Transition Metals 20.3 Coordination
Compounds 20.4 Isomerism 20.5 Bonding in
Complex Ions The localized Electron Model 20.6
The Crystal Field Model 20.7 The Molecular
Orbital Model 20.8 The Biological Importance of
Coordination Complexes
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Vanadium metal (center) and in solution as
V2(aq), V3(aq), VO2(aq), and VO2(aq), (left
to right).
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Figure 20.1 Transition elements on the periodic
table
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Calcite with traces of Iron
Source Fundamental Photographs
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Quartz
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Wulfenite
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Rhodochrosite
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Aqueous solutions containing metal ions
Co2 Mn2 Cr3 Fe3
Ni2
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Molecular model The CO(NH3)63 ion
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Figure 20.2 plots of the first (red dots) and
third (blue dots) ionization energies for the
first-row transition metals
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Figure 20.3 Atomic radii of the 3d, 4d, and 5d
transition series.
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Transition metals are often used to construct
prosthetic devices, such as this hop joint
replacement.
Source Science Photo Library
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Liquid titanium(IV) chloride being added to
water, forming a cloud of solid titanium oxide
and hydrochloric acid.
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Colors of Representative Compounds of the Period
4 Transition Metals
b
d
f
h
j
g
a
c
e
i
a Scandium oxide b Titanium(IV) oxide c
Vanadyl sulfate dihydrate d Sodium chromate e
Manganese(II) chloride tetrahydrate
f Potassium ferricyanide g Cobalt(II)
chloride hexahydrate h Nickel(II) nitrate
hexahydrate i Copper(II) sulfate pentahydrate
j Zinc sulfate heptahydrate
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Orbital Occupancy of the Period 4 MetalsI
Element Partial Orbital Diagram
Unpaired Electrons
4s 3d
4p
Sc

1 Ti

2 V

3 Cr

6 Mn
5
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Orbital Occupancy of the Period 4 MetalsII
Element Partial Orbital Diagram
Unpaired Electrons
4s 3d
4p
Fe

4 Co

3 Ni

2 Cu

1 Zn

0
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Oxidation States and d-Orbital Occupancy of the
Period 4 Transition Metals
3B 4B 5B
6B 7B 8B 8B 8B 1B
2B Oxidation (3) (4) (5)
(6) (7) (8) (9) (10)
(11) (12) State Sc Ti
V Cr Mn Fe Co
Ni Cu Zn
0 0 0 0 0
0 0 0 0
0 0 (d1) (d2)
(d3) (d5) (d5) (d6) (d7)
(d 8) (d10) (d10) 1
1 1 1
1 1 1
(d3) (d5) (d5)
(d7) (d8) (d10) 2
2 2 2 2 2 2
2 2 2
(d2) (d3) (d4) (d5) (d6)
(d7) (d8) (d9) (d10) 3
3 3 3 3 3
3 3 3 3
(d0) (d1) (d2) (d3) (d4)
(d5) (d6) (d7) (d8) 4
4 4 4 4 4
4 4
(d0) (d1) (d2) (d3) (d4 )
(d5) (d6) 5
5 5 5 5
(d0) (d1)
(d2) (d4) 6
6 6 6

(d0) (d1) (d2) 7
7 (d0)
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Figure 20.4 Titanium bicycle
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Figure 20.5 Structures of the chromium (VI)
anions
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Manganese nodules on the sea floor
Source Visuals Unlimited
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Aqueous solution containing the Ni2 ion
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Alpine Pennycress
This plant can thrive on soils contaminated with
Zn and Cd, concentrating them in the stems, which
can be harvested to obtain these elements.
Source USDA photo
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Figure 20.6 Ligand arrangements for
coordination numbers 2, 4, and 6
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Figure 20.7 a) Bidentate ligand
ethylene-diamine can bond to the metal ion
through the lone pair on each nitrogen atom, thus
forming two coordinate covalent bonds. B) Ammonia
with one electron pair to bond.
a)
b)
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Figure 20.8 The coordination of EDTA with a 2
metal ion.
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Rules for Naming Coordination Compounds - I

• As with any ionic compound, the cation is named
  before the anion
• In naming a complex ion, the ligands are named
  before the metal ion.
• In naming ligands, an o is added to the root
  name of an anion. For
• example, the halides as ligands are called
  fluoro, chloro, bromo, and
• iodo hydroxid is hydroxo and cyanide is
  cyano. For a neutral the
• name of the molecule is used, with the
  exception of H2O, NH3, CO,
• and NO, as illustrated in table 20.14.
• 4) The prefixes mono-, di-, tri-, tetra-,
  penta-, and hexa- are used to
• denote the number of simple ligands. The
  prefixes bis-, tris-, tetrakis-,
• and so on, are also used, especially for
  more complicated ligands or
• ones that already contain di-, tri-, and so
  on.
• 5) The oxidation state of the central metal ion
  is designated by a Roman
• numeral in parentheses.

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Rules for Naming Coordination Compounds - II

• When more than one type of ligand is present,
  ligands are named in
• alphabetical order. Prefixes do not affect
  the order.
• If the complex ion has a negative charge, the
  suffix ate is added to
• the name of the metal. Sometimes the Latin
  name is used to identify
• the metal (see table 20.15).

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Example 20.1 (P 947)

• Give the systematic name for each of the
  following coordination
• compounds
• a) Co(NH3)5ClCl2 b) K3Fe(CN)6
  c) Fe(en)2(NO2)22SO4
• Solution
• Ammonia molecules are neutral, Chloride is -1, so
  cobalt is 3
• the name is therefore
• 
  pentaamminechlorocobalt(III) chloride
• 3 K ions, 6 CN- ions, therefore the Iron must
  have a charge of 3
• the complex ion is Fe(CN)6-3, the
  cyanide ligands are cyano, the
• latin name for Iron is ferrate, so the
  name is
• 
  potassium hexacyanoferrate(III)
• c) Four NO2-, one SO4-2, ethylenediamine is
  neutral so the iron is 3
• the name is therefore
• 
  bis(ethylenediamine)dinitroiron(III) sulfate

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An aqueous solution of Co(NH3)5ClCl2
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Solid K3Fe(CN)6
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Figure 20.9 Classes of isomers
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Structural Isomerism
Coordination isomerism the composition of the
complex ion varies.
consider Cr(NH3)5SO4Br and
Cr(NH3)5BrSO4 another example is
Co(en)3Cr(ox)3 and Cr(en)3Co(ox)3
ox represents the oxalate ion. Linkage
isomerism the composition of the complex ion is
the, but the point of attachment of at
least one of the ligands is different.
Co(NH3)4(NO2)ClCl
Tetraamminechloronitrocobalt(III) chloride
(yellow)
Co(NH3)4(ONO)ClCl Tetraamminechloronitri
tocobalt(III) chloride (red)
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Figure 20.10 As a ligand, NO2- can bond to a
metal ion (a) through a lone pair on the nitrogen
atom (b) through a lone pair on one of the oxygen
atoms
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Figure 20.11 (a) The cis isomer of Pt(NH3)2Cl2
(yellow). (b) the trans isomer of Pt(NH3)2Cl2
(pale yellow).
Cis - yellow
Trans pale yellow
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Figure 20.12 (a) The trans isomer of
Co(NH3)4Cl21. The chloride ligands are directly
across from each other. (b) The cis isomer of
Co(NH3)4Cl21.
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Figure 20.13 Unpolarized light consists of
waves vibrating in many different planes
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Figure 20.14 Rotation of the plane of
polarized light by an optically active substance.
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Figure 20.15 human hand has a nonsuperimposed
mirror image
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Figure 20.15 human hand has a nonsuperimposed
mirror image (contd)
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Figure 20.16 Isomers I and II of Co(en)33 are
mirror images (the mirror image of I is identical
to II) that cannot be superimposed.
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Figure 20.17 Trans isomer of Co(en)2Cl2 and
its mirror image are identical(superimposable)
(b) cis isomer of Co(en)2Cl2
No Optical activity Does
have Optical activity
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Figure 20.18 Some cis complexes of platinum and
palladium that show significant antitumor
activity.
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Figure 20.19 Set of six d2sp3 hybrid orbitals
on CO3
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Figure 20.20 Hybrid orbitals required for
tetrahedral square planar and linear Complexes
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Figure 20.21 Octahedral arrangement and
d-orbitals
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Figure 20.22 Energies of the 3d orbitals for a
metal ion in a octahedral complex.
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Figure 20.23 possible electron arrangements in
the split 3d orbitals of an octahedral complex of
Co3
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Example 20.4 (P958) The Fe(CN)6-3 ion is known
to have one unpaired electron. Does the
CN- ligand produce a strong or weak
field? Solution Since the ligand is CN- and the
overall complex ion charge is -3, the metal ion
must be Fe3, which has a 3d5 electron
configuration. The two possible arrangements of
the five electrons in the d orbitals split by
the octahedrally arranged ligands are The
strong-field case gives one unpaired electron,
which agrees with the experimental observation.
The CN- ion is a strong-field ligand toward the
Fe3 ion.
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The Spectrochemical Series
CN- gt NO2- gt en gt NH3 gt H2O gt OH- gt F- gt Cl- gt
Br- gt I- Strong-field
Weak-field ligands

ligands (large )
(small
) The magnitude of for a given ligand
increases as the charge on The metal ion
increases.
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Example 20.5 (P 959) Perdict the number of
unpaired electrons in the complex ion
Cr(CN)64-. Solution The net charge of 4-
means that the metal ion must be Cr2
(-62-4), which has a 3d4 electron
configuration. Since CN- is a strong-field
ligand, the correct crystal field diagram for
Cr(CN)64- is The complex ion will have
two unpared electrons. Note that the CN- ligand
produces such a large splitting that two of the
electrons will be Pared in the same orbital
rather than force one electron up through
the Large energy gap .
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Figure 20.24 Visible spectrum
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Figure 20.25 (a) when white light shines on a
filter that absorbs wavelengths (b) because the
complex ion
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Figure 20.26 The complex ion Ti(H2O)63
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Figure 20.27 Tetrahedral and octahedral
arrangements of ligands shown inscribed in cubes.
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Figure 20.28 Crystal field diagrams for
octahedral and tetrahedral complexes
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Figure 20.29 Crystal field diagram for a square
planar complex oriented in the xy plane (b)
crystal field diagram for a linear complex
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Figure 20.30 Octahedral arrangement of ligands
showing their lone pair orbitals
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Figure 20.31 The MO energy-level diagram for an
octahedral complex ion
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Figure 20.32 MO energy-level diagram for
CoF63-, which yields the high-spin
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Figure 20.33 The heme complex in which an Fe2
ion is coordinated to four nitrogen atoms of a
planar porphyrin ligand.
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Figure 20.35 Representation of the myoglobin
molecule
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Figure 20.36 Representation of the hemoglobin
structure
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Figure 20.37 Normal red blood cell (right) and
a sickle cell, both magnified 18,000 times.
Source Visuals Unlimited
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Hemoglobin and the Octahedral Complex in Heme
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Figure 20.34 Chlorophyll is a porphyrin complex
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The Tetrahedral Zn2 Complex in Carbonic Anhydrase