Transcript Chapter 20-23 The Transition Elements.ppt

Central South University
Mn(VII)
Cr(VI)
V(V)
Chapter 14
The Transition Elements
and Their Chemistry
College of Chemistry and Chemical Engineering
Central South University
14.1 Properties of the
Transition Elements
14.1 Properties of the Transition Elements
14.2 The Inner Transition Elements
14.3 Highlights of Selected Transition
Metals
14.4 Coordination Compounds
14.5 Theoretical Basis for the Bonding and
Properties of Complexes
College of Chemistry and Chemical Engineering
Central South University
The transition elements (d block) and inner transition
elements (f block) in the periodic table.
College of Chemistry and Chemical Engineering
Central South University
The Period 4 transition metals
College of Chemistry and Chemical Engineering
Central South University
The Period 4 transition metals
College of Chemistry and Chemical Engineering
Central South University
The Period 4 transition metals
College of Chemistry and Chemical Engineering
Central South University
Orbital Occupancy of the Period 4 Transition Metals
College of Chemistry and Chemical Engineering
Central South University
Sample Problem 14.1
PROBLEM:
Writing Electron Configurations of Transition
Metal Atoms and Ions
Write condensed electron configurations for the following: (a) Zr;
(b) V3+; (c) Mo3+. (Assume that elements in higher periods
behave like those in Period 4.)
PLAN: The general configuration is [noble gas] ns2(n-1)dx. Recall that in ions
the ns electrons are lost first.
SOLUTION:
(a) Zr is the second element in the 4d series: [Kr]5s24d2.
(b) V is the thired element in the 3d series: [Ar]4s23d3. In forming V3+,
three electrons are lost (two 4s and one 3d), so V3+ is a d2 ion: [Ar]3d10.
(c) Mo lies below Cr in Group 6B(6), so we expect the same except in
configuration as for Cr. Thus, Mo is [Kr]5s14d5. In forming the ion, Mo
loses the one 5s and two of the 4d electrons to become a 4d3 ion: [Kr]4d3.
College of Chemistry and Chemical Engineering
Central South University
Horizontal trends in key atomic properties
of the Period 4 elements.
College of Chemistry and Chemical Engineering
Central South University
Vertical trends in key properties within
the transition elements
College of Chemistry and Chemical Engineering
Central South University
Aqueous oxoanions of transition elements.
Mn(II)
Mn(VI)
Mn(VII)
One of the most
characteristic
chemical properties of
these elements is the
occurrence of multiple
oxidation states.
Mn(VII)
Cr(VI)
V(V)
College of Chemistry and Chemical Engineering
Central South University
Oxidation states and d-orbital occupancy of the period 4
transition metals
College of Chemistry and Chemical Engineering
Central South University
Standard electrode potentials of
period 4 M 2+ ions
College of Chemistry and Chemical Engineering
Central South University
Colors of representative compounds of the Period 4 transition metals.
sodium chromate
titanium oxide
scandium oxide
vanadyl sulfate
dihydrate
nickel(II) nitrate
hexahydrate
potassium
ferricyanide
manganese(II)
chloride
tetrahydrate
cobalt(II)
chloride
hexahydrate
zinc sulfate
heptahydrate
copper(II)
sulfate
pentahydrate
College of Chemistry and Chemical Engineering
Central South University
Some properties of group 6B(6) elements
College of Chemistry and Chemical Engineering
Central South University
Sample Problem 14.2
PROBLEM:
PLAN:
Finding the Number of Unpaired Electrons
The alloy SmCo5 forms a permanent magent because both
samarium and cobalt have unpaired electrons. How many
unpaired electrons are in the Sm atom (Z = 62)?
Write the condensed configuration of Sm and, using Hund’s
rule and the aufbau principle, place electrons into a partial
orbital diagram.
SOLUTION: Sm is the eighth element after Xe. Two electrons go into the 6s
sublevel and the remaining six electrons into the 4f (which fills
before the 5d).
Sm is [Xe]6s24f6
6s
4f
5d
There are 6 unpaired e- in Sm.
College of Chemistry and Chemical Engineering
Central South University
The bright colors of chromium (VI) compounds.
College of Chemistry and Chemical Engineering
Central South University
Some oxidation states of manganese
Orbital Occupancy
*Most common states in bold face.
College of Chemistry and Chemical Engineering
Central South University
Steps in producing a black-and-white negative.
College of Chemistry and Chemical Engineering
Central South University
Components of a coordination compound.
models
wedge diagrams
chemical formulas
College of Chemistry and Chemical Engineering
Central South University
Structures of Complex Ions:
Coordination Numbers, Geometries, and Ligands
•Coordination Number - the number of ligand atoms that are bonded
directly to the central metal ion. The coordination number is specific for
a given metal ion in a particular oxidation state and compound.
•Geometry - the geometry (shape) of a complex ion depends on the
coordination number and nature of the metal ion.
•Donor atoms per ligand - molecules and/or anions with one or more
donor atoms that each donate a lone pair of electrons to the metal ion to
form a covalent bond.
College of Chemistry and Chemical Engineering
Central South University
Coordination numbers and shapes of some complex ions
College of Chemistry and Chemical Engineering
Central South University
Some common ligands in coordination compounds
College of Chemistry and Chemical Engineering
Central South University
Names of some neutral and anionic ligands
Names of some metal
ions in complex anions
College of Chemistry and Chemical Engineering
Central South University
Formulas and Names of Coordination Compounds
Rules for writing formulas:
1. The cation is written before the anion.
2. The charge of the cation(s) is balanced by the
charge of the anion(s).
3. In the complex ion, neutral ligands are written before
anionic ligands, and the formula for the whole ion is
placed in brackets.
College of Chemistry and Chemical Engineering
Central South University
Formulas and Names of Coordination Compounds
Rules for naming complexes:
continued
1. The cation is named before the anion.
2. Within the complex ion, the ligands are named, in
alphabetical order, before the metal ion.
3. Neutral ligands generally have the molecule name, but
there are a few exceptions. Anionic ligands drop the ide and add -o after the root name.
4. A numerical prefix indicates the number of ligands of a
particular type.
5. The oxidation state of the central metal ion is given by a
Roman numeral (in parentheses).
6. If the complex ion is an anion we drop the ending of the
metal name and add -ate.
College of Chemistry and Chemical Engineering
Central South University
Sample Problem 14.3
PROBLEM:
Writing Names and Formulas of Coordination
Compounds
(a) What is the systematic name of Na3[AlF6]?
(b) What is the systematic name of [Co(en)2Cl2]NO3?
(c) What is the formula of tetraaminebromochloroplatinum(IV)
chloride?
(d) What is the formula of hexaaminecobalt(III) tetrachloroferrate(III)?
PLAN:
Use the rules presented -
SOLUTION:
and
.
(a) The complex ion is
3-.
[AlF6] Six
(hexa-) fluorines (fluoro-) are the ligands - hexafluoro
Aluminum is the central metal atom - aluminate
Aluminum has only the +3 ion so we don’t need Roman
numerals.
sodium hexafluoroaluminate
College of Chemistry and Chemical Engineering
Central South University
Sample Problem 14.3
Writing Names and Formulas of Coordination
Compounds
continued
(b) There are two ligands, chlorine and ethylenediamine dichloro, bis(ethylenediamine)
The complex is the cation and we have to use Roman numerals for
the cobalt oxidation state since it has more than one - (III)
The anion, nitrate, is named last.
dichlorobis(ethylenediamine)cobalt(III) nitrate
(c)
Pt4+
ClCl
tetraaminebromochloroplatinum(IV) chloride
4 NH3
Br-
[Pt(NH3)4BrCl]Cl2
(d)
6 NH3
Co3+
4 Cl-
Fe3+
hexaaminecobalt(III) tetrachloro-ferrate(III)
[Co(NH3)6][Cl4Fe]3
College of Chemistry and Chemical Engineering
Central South University
Some coordination compounds of cobalt studied by werner
College of Chemistry and Chemical Engineering
Central South University
Important types of isomerism in coordination compounds.
ISOMERS
Same chemical formula, but different properties
Constitutional (structural) isomers
Stereoisomers
Atoms connected differently
Different spatial arrangement
Coordination
isomers
Linkage
isomers
Ligand and
counter-ion
exchange
Different donor
atom
Geometric (cistrans) isomers
(diastereomers)
Different
arrangement
around metal ion
Optical isomers
(enantiomers)
Nonsuperimposable
mirror images
College of Chemistry and Chemical Engineering
Central South University
Linkage isomers
College of Chemistry and Chemical Engineering
Central South University
Geometric (cis-trans) isomerism.
College of Chemistry and Chemical Engineering
Central South University
Optical isomerism in an
octahedral complex ion.
College of Chemistry and Chemical Engineering
Central South University
Sample Problem 14.4
PROBLEM:
PLAN:
Determining the Type of Stereoisomerism
Draw all stereoisomers for each of the following and state the type
of isomerism:
(a) [Pt(NH3)2Br2]
(b) [Cr(en)3]3+ (en = H2NCH2CH2NH2)
Determine the geometry around each metal ion and the nature of
the ligands. Place the ligands in as many different positions as
possible. Look for cis-trans and optical isomers.
SOLUTION: (a) Pt(II) forms a square planar complex and there are two pair
of monodentate ligands - NH3 and Br.
Br
NH3
H3N
Pt
H3N
Pt
Br
trans
Br
H3N
Br
These are geometric isomers;
they are not optical isomers
since they are superimposable
on their mirror images.
cis
College of Chemistry and Chemical Engineering
Central South University
Sample Problem 14.5
Determining the Type of Stereoisomerism
(b) Ethylenediamine is a bidentate ligand. Cr3+ is
hexacoordinated and will form an octahedral geometry.
continued
Since all of the ligands are identical, there will be no geometric isomerism
possible.
3+
3+
N
N
N
N
N
N
Cr
Cr
N
The mirror images are
nonsuperimposable
and are therefore
optical isomers.
N
N
N
N
N
rotate
3+
N
N
N
Cr
N
N
N
College of Chemistry and Chemical Engineering
Central South University
Hybrid orbitals and bonding in the octahedral [Cr(NH3)6]3+ ion.
College of Chemistry and Chemical Engineering
Central South University
Hybrid orbitals and bonding in the square planar [Ni(CN)4]2- ion.
College of Chemistry and Chemical Engineering
Central South University
Hybrid orbitals and bonding in the tetrahedral [Zn(OH)4]2- ion.
College of Chemistry and Chemical Engineering
Central South University
An artist’s wheel.
College of Chemistry and Chemical Engineering
Central South University
Relation between absorbed and observed colors
College of Chemistry and Chemical Engineering
Central South University
The five d-orbitals in an octahedral field of ligands.
College of Chemistry and Chemical Engineering
Central South University
Splitting of d-orbital energies by an octahedral field of
ligands.
D is the splitting energy
College of Chemistry and Chemical Engineering
Central South University
The effect of ligand on splitting energy.
College of Chemistry and Chemical Engineering
Central South University
The color of [Ti(H2O)6]3+.
College of Chemistry and Chemical Engineering
Central South University
Effects of the metal oxidation state and of ligand identity on color.
[V(H2O)6]3+
[V(H2O)6]2+
[Cr(NH3)6]3+
[Cr(NH3)5Cl ]2+
College of Chemistry and Chemical Engineering
Central South University
The spectrochemical series.
•For a given ligand, the color depends on the oxidation state of the metal ion.
•For a given metal ion, the color depends on the ligand.
I- < Cl- < F- < OH- < H2O < SCN- < NH3 < en < NO2- < CN- < CO
WEAKER FIELD
STRONGER FIELD
SMALLER D
LARGER D
LONGER 
SHORTER 
College of Chemistry and Chemical Engineering
Central South University
Sample Problem 14.6
PROBLEM:
Ranking Crystal Field Splitting Energies for
Complex Ions of a Given Metal
Rank the ions [Ti(H2O)6]3+, [Ti(NH3)6]3+, and [Ti(CN)6]3- in terms of
the relative value of D and of the energy of visible light absorbed.
PLAN: The oxidation state of Ti is 3+ in all of the complexes so we are
looking at the crystal field strength of the ligands. The stronger the
ligand the greater the splitting and the higher the energy of the light
absorbed.
SOLUTION:
The field strength according to
is CN- > NH3 > H2O. So the
relative values of D and energy of light absorbed will be
[Ti(CN)6]3- > [Ti(NH3)6]3+ > [Ti(H2O)6]3+
College of Chemistry and Chemical Engineering
Central South University
High-spin and low-spin complex ions of Mn2+.
College of Chemistry and Chemical Engineering
Central South University
Orbital occupancy for high- and low-spin complexes
of d4 through d7 metal ions.
high spin:
weak-field
ligand
low spin:
strong-field
ligand
high spin:
weak-field
ligand
low spin:
strong-field
ligand
College of Chemistry and Chemical Engineering
Central South University
Sample Problem 14.7
PROBLEM:
PLAN:
Identifying Complex Ions as High Spin or Low Spin
Iron (II) forms an essential complex in hemoglobin. For each of the
two octahedral complex ions [Fe(H2O)6]2+ and [Fe(CN)6]4-, draw an
orbital splitting diagram, predict the number of unpaired electrons,
and identify the ion as low or high spin.
The electron configuration of Fe2+ gives us information that the
iron has 6d electrons. The two ligands have field strengths shown
in
.
potential energy
Draw the orbital box diagrams, splitting the d orbitals into eg and
t2g. Add the electrons noting that a weak-field ligand gives the
maximum number of unpaired electrons and a high-spin complex
and vice-versa.
[Fe(CN)6]42+
[Fe(H2O)6]
SOLUTION:
4 unpaired e-eg
(high spin)
eg
no unpaired e-(low spin)
t2g
t2g
College of Chemistry and Chemical Engineering
Central South University
Splitting of d-orbital energies by a tetrahedral field
and a square planar field of ligands.
tetrahedral
square planar
College of Chemistry and Chemical Engineering
Central South University
Hemoglobin and the octahedral complex in heme.
College of Chemistry and Chemical Engineering
Central South University
Some transition metal trace elements in humans
College of Chemistry and Chemical Engineering
Central South University
The tetrahedral Zn2+ complex in carbonic anhydrase.
College of Chemistry and Chemical Engineering