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Organic vs Inorganic
What is inorganic chemistry?
Inorganic Chemistry
Organimetallic
Bioinorganic
Introduction to Inorganic Chemistry
Organic vs Inorganic
Introduction to Inorganic Chemistry
Organic vs Inorganic
Introduction to Inorganic Chemistry
8.11 Ligand chirality
8.10 Octahedral complexes
8.9 Trigonal-bipyramidal and square-pyramidal complexes
8.8 Tetrahedral complexes
8.7 Square-planar complexes
Isomerism and chirality
8.6 Nomenclature
8.5 Representative ligands
Ligands and nomenclature
8.4 Polymetallic complexes
8.1 High coordination numbers
8.2 Intermediate coordination numbers
8.1 Low coordination numbers
Constitution and geometry
Chapter 8 An Introduction to Coordination
Compounds
Ligand can be a atom, ion, and molecules.
What is ligand?
More specifically, a transition metal surrounded by
neutral molecules or anions with a definite geometry.
What is coordination compound?
Coordination compounds include compound
composed of a metal atom or ion and one or more
ligands that formally donate electrons to the metal.
History
Copper(II) sulfate ("sulphate" in most Commonwealth nations) is the
chemical compound with the formula CuSO4. This salt exists as a series of
compounds that differ in their degree of hydration. The anhydrous form is
a pale green or gray-white powder, while the pentahydrate, the most
commonly encountered salt, is bright blue. This hydrated copper sulfate
occurs in nature as the mineral called chalcanthite. The archaic name for
copper(II) sulfate is "blue vitriol" or "bluestone"
The key breakthrough occurred when Alfred Werner proposed,
Aureolin
(sometimes
called
Cobalt
Yellow)
pigment used
in oil and
inter alia,
that Co(III)
bears
six ligands
inisana octahedral
geometry.
watercolor painting. Its color index name is PY40 (40th entry on list of
yellow pigments). It was first made in 1851 and its chemical composition is
potassium cobaltinitrite.
Prussian blue
(German: Preußischblau or Berliner Blau, in English Berlin
History
blue) is a dark blue pigment used in paints and formerly in blueprints.
Prussian blue was discovered by accident by painter Heinrich Diesbach in
What
compound?
Berlin in 1704-5,
whichisiscoordination
why it is also known
as Berlin blue. (Diesbach
was Coordination
attempting to complexes
create a paint
with
a red- hue.)
It has
different
were
known
although
notseveral
understood
chemical
iron(III) ferrocyanide,
in anynames,
sense these
- sincebeing
the beginning
of chemistry,ferric
e.g. ferrocyanide,
Prussian
iron(III)
hexacyanoferrate(II),
and
ferric hexacyanoferrate. Commonly and
blue,
Aureolin, and copper
vitriol.
conveniently it is simply called "PB.
For complexes with more than one type of ligand, Werner succeeded in
explaining
the number
of first
isomers
observed.
For structures
exemple, he
the
In 1893, Werner
was the
to propose
correct
forexplained
coordination
existence of containing
two isomers
of "Co(NH
Clwhich
and
one purple.
3)4in
3", oneagreen
compounds
complex
ions,
central
transition
metal
Werner
proposed that
are
geometric
isomers of formula
atom is surrounded
by these
neutral
ortwo
anionic
ligands.
- ion dissociated as confirmed by conductivity
[Co(NH
withknown
one Clthat
3)4Cl2]Cl,
For example,
it was
cobalt forms a "complex" with formula
measurements.
The Co atom is surrounded by four NH and two Cl ligands
CoCl
3•6NH3, but the nature of the association indicated3by the dot was
at
the vertices
of an proposed
octahedron.
green [Co(NH
isomer is) ]Cl
"trans"
with the two
mysterious.
Werner
theThe
structure
3 6
3, with the Co3+
Cl
at opposite
vertices,
and the purple is "cis" with the two Cl at
ionligands
surrounded
by six NH
3 at the vertices of an octahedron. The three Cladjacent
vertices.
are
dissociated
as free ions, which he confirmed by measuring the
electrical conductivity of the compound in aqueous solution.
Alfred Werner
Nobel Prize for Chemistry
1913
He resolved the first coordination complex into optical isomers,
overthrowing the theory that chirality was necessarily associated
with carbon compounds.
The theory allows one to understand the difference between
coordinated and ionic chloride in the cobalt ammine chlorides
and to explain many of the previously inexplicable isomers.
The key breakthrough occurred when Alfred Werner proposed,
inter alia, that Co(III) bears six ligands in an octahedral geometry.
Coordination complexes were known - although not understood
in any sense - since the beginning of chemistry, e.g. Prussian
blue, Aureolin, and copper vitriol.
What is coordination compound?
History
What is ligand?
The complex of the metal with the inner sphere ligands is then
called a complex ion (which can be either cationic or anionic).
The complex, along with its counter ions, is called a coordination
compound. The size of a ligand is indicated by its cone angle.
The ligands that are directly bonded to the metal (that is, share
electrons), are called "inner sphere" ligands.
If the inner-sphere ligands do not balance the charge of the
central atom, this may be done by simple ionic bonding with
another set of counter ions (the "outer-sphere" ligands).
In chemistry, a ligand is an atom, ion, or molecule that generally
donates one or more of its electrons through a coordinate
covalent bond to one or more central atoms or ions (these
ligands act as a Lewis base).
History
Electron counting is key in understanding organometallic
chemistry. The 18-electron rule is helpful in predicting the
stabilities of organometallic compounds. Organometallic
compounds which have 18 electrons (filled s, p, and d orbitals)
are relatively stable. This suggests the compound is isolable, but
it can result in the compound being inert.
Organometallic compounds find practical use in stoichiometric
and catalytically active compounds.
Organometallic chemistry combines aspects of inorganic
chemistry and organic chemistry.
Organometallic chemistry is the study of chemical compounds
containing bonds between carbon and a metal.
Organometallic Compound
History
Cluster: Ligands are all of the above but also include other
metals as ligands.
Example Ru3(CO)12
Bioinorganic: Ligands are those provided by nature, especially
including the side chains of amino acids, and many cofactors
such as porphyrins.
Example: hemoglobin
Organometallic: Ligands are organic (alkenes, alkynes, alkyls) as
well as "organic-like" ligands such as phosphines, hydride, and
CO.
Classical (or "Werner Complexes"): Ligands in classical
coordination chemistry bind to metals.
Nomenclature
– Common Monodentate Ligands
Size: ligand, central atom or ion
Electron density
Multiple bond
{[Mn(H2O)6]2+SO42-} vs
[Mn(H2O)5SO4]
In an inner-sphere complex, the ligands are attached directly to a
central metal ion: the number of ligands depends on the size of
the metal, the identity of the ligands, and the electronic
interactions.
Constitution and geometry
Position of these complexes in
periodic table.
Coordination number 3: with bulky ligands
Coordination number 2; Cu+, Ag+, Au+, they often gain
additional ligands to form three- or four- coordinate complexes.
Constitution and geometry
8.1 Low coordination numbers
Square-planar complexes are typically observed
for metals with d8 configurations (Rh+, Ir+, Pd2+,
Pt2+, Au3+).
Tetrahedral complexes are favoured over higher
coordinate complexes if the central atom is small
or the ligands large.
- ligand-ligand repulsions override the energy
advantage of forming more metal-ligand bonds
Four-coordination:
Coordination number 4, 5, 6.
They include the vast majority of complexes.
Constitution and geometry
8.2 Intermediate coordination numbers
Geometric isomerism
Constitution and geometry
8.2 Intermediate coordination numbers
Distortions from these ideal geometries are common.
Square pyramidal or trigonal bipyramidal.
The energies of the various geometries of five-coordinate
complexes differ little from one another and such complexes are
often fluxional.
Five-coordination:
Constitution and geometry
8.2 Intermediate coordination numbers
[Fe(CO)5]; crystal, NMR, IR
Berry pseudorotation
Constitution and geometry
8.2 Intermediate coordination numbers