Chapter 22
The “d”-Block Elements
&
Coordination Chemistry
Hill, Petrucci, McCreary & Perry 4th Ed.
The “d-block” Elements
Groups 3-12 in the Periodic chart
associated with the filling of the 3d, 4d, 5d
electronic shells in the Atom.
Groups 3 and 12 differ significantly from
the others: They are softer, lower
melting, have one principal oxidation
state and they tend to form colorless
compounds.
Groups 4-11 in the Periodic Chart
“The transition Metals”
They tend to be high melting/boiling, very
hard, magnetic, have variable (multiple)
oxidation states (but 0 and 2 are common
to all) and many of their compounds are
colored. They form Coordination
Compounds.
The highest melting/boiling and hardest
are found in groups 5 & 6
1
Transition Metal Electron Configurations
Core electrons not
used in bonding
Lost first origin of common
+2 oxidation state
[Rare Gas] s 2 dn-2
Ions: M2+ M3+ M4+ are far
from a rare gas configuration.
Lost consecutively as the
oxidation state increases
Ions have vacant s, p, d atomic orbitals and are Lewis Acids
Coordination Chemistry: Molecules having "lone pairs" of electrons
are Lewis Bases and can chemically combine with the Lewis Acid
Cations and form "Coordination Compounds".
Ligands
F-
Monodentate Ligands
Br -
Cl -
I-
O H-
OH2
PH3
NH3
Despite the multiple "lone pairs" only ONE is available for bonding!
lone pairs
Cyanide
O
C N-
H3C C
bond pairs
O
Oxalate
ethylenediamine
O
CH2 CH2
C C
O
"ox"
Mn+
Chelates:
Ligands
O
acetate
Bidentate Ligands
Both of these
oxygens bind
NH2
O
form rings
NH2
"en"
Mn+
Tridentate Ligands
"dien"
CH2 CH2
NH2
CH2 CH2
NH2
NH
diethylenetriamine
Polydentate Ligands
O
O
O
O
C CH2
"EDTA"
O
H2C C
N CH2 CH2 N
C CH2
H2C C
ethylenediaminetetraacetate
O
O
O
2
Werner’s Theory of Coordination
Primary Valence: Oxidation State
Secondary Valence: Coordination Number
Iron (III) - Fe3+ = Primary Valence
Hexaquoiron(III) =>
[Fe(H2O)6]3+
Hexammineiron(III) =>
[Fe(NH3)6]3+
secondary
valence
[Fe(CN)6]3-
Hexacyanoiron(III) =>
note change in charge
[coordination sphere]
CN-
algebraic sum of charges
Coordination Number & Structure
Coordination
Number CN
Possible
Structures
2
Linear
3
Trigonal
Examples
Cl
R3P
Planar, all angles 120E
Ag Cl
PR3
Pt
PR3
Coordination Number & Structure
Coordination
Number CN
4
Possible
Structures
Examples
Tetrahedral
all angles 109.5 o
Cl
Cl
Ni
Cl
Cl
NC
Square Planar
NC
all angles 90.0o
Ni
CN
CN
3
Coordination Number & Structure
Coordination
Number CN
Possible
Structures
5
Trigonal Bipyramid
Examples
Cl
Cl
Ni
Cl
Cl
angles 120.0 o
angles 90.0 o
Square Pyramid
Cl
PR3
NC
CN
Co
NC
CN
all angles 90.0o
Coordination Number & Structure
Coordination
Number CN
Possible
Structures
NC
Very Common
Very Important
PR3
NC
PR3
PR3
Octahedron
all angles 90.0o
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NC
Examples
M
CN
CN
NC
Trigonal Prism
Uncommon
angles 109.5o
CN
Co
CN
PR3
Not Responsible for this
Structure & Isomerism
What must be the structure of [NiCl2Br2]2- if it
is known to have two distinct isomers? Draw
them:
4
Structure & Isomerism
What must be the structure of [NiCl2Br2]2- if it
is known to have only one isomer? Draw it:
Stereoisomerism in Octahedral
[MA2B4] Coordination Complexes
NH3
Examine the two
unique Cl ligands!
H3N
NH3
"transoid"
opposite
H3N
Cl
Cl
Co
Co
H3N
Cl
"cisoid" Cl
adjacent
H3N
NH3
NH3
trans Isomer
cis Isomer
Stereoisomerism in Octahedral
[MA3B3] Coordination Complexes
Examine the three unique
NH3 ligands making triangles!
NH3
O2N
H3N
NH3
NO2
Co
Co
O2N
H3N
NO2
NO2
fac Isomer
parallel
planes
NO2
NH3
mer Isomer
perpendicular
planes
5
Optical Isomerism in Octahedral
[MA2en2] Coordination Complexes
H2C
H2C
CH2
NH2
NH2
H2N
Cl
CH2
NH2
Cl
Co
Co
H2N
NH2
Cl
CH2
CH2
Cl
CH2
NH2
H2N
"d"-cis Isomer
"l"-cis Isomer
"l" = levorotatory
mirror
plane
"d" = dextrorotatory
CH2
Optical Isomerism in Octahedral
[MA2en2] Coordination Complexes
Note: The "d" isomer does not
superimpose when rotated 180
N 2
H2NH
CH2
CH2
CH2
These two positions
are interchanged
NH
NH22
Cl
Co CH2
CH2
NH
NH22
CH2
Cl
CH2
Note: The bottom "en"
H22N
CH
2
flips from front to back.
Optical Isomerism in Octahedral
[MA2en2] Coordination Complexes
Note: The "d" isomer does not
superimpose when rotated 180
H2N
These two positions
are interchanged
CH2
NH2
Cl
CH2
Co CH2
NH2
CH2
CH2
NH2
Cl
Co
NH2
NH2
CH2
Cl
H2N
Note: The bottom "en"
flips from front to back.
"d"-cis Isomer
"d" = dextrorotatory
Cl
CH2
H2N
CH2
"l"-cis Isomer
"l" = levorotatory
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Consequences of Optical Isomerism
•Optically active molecules have identical
chemical and physical properties, unless
the reacting species or the physical
technique itself possesses chirality, itself
optically active.
•Light is chiral. Plane polarized light will
be rotated to the right or to the left a
fixed number of degrees depending on
which optical isomer is in the polarizer.
7