Download Transition Metales

Transition Metals and
Coordination Chemistry
Dr.Monther F.Salem
d-block elements transition metals
d-block elements are:
• all metals
• all have partially filled d subshells
• exhibit horizontal & vertical similarities
• alloys & compounds are important components
of materials in modern world
• most first-row transition metals are essential
for life
Transition Metals
• the properties of the transition metals are similar to
each other
– and very different to the properties of the main group
metals
– high melting points, high densities, moderate to very hard,
and very good electrical conductors
• in general, the transition metals have two valence
electrons – we are filling the d orbitals in the shell
below the valence
– Group 1B and some others have 1 valence electron due to
“promotion” of an electron into the d sublevel to fill it
– form ions by losing the ns electrons first, then the (n – 1)d
Transition Metals
• Some differences
– Melting point, Tungsten melts 3400°, while mercury -39°C
– Some soft, like sodium that can be cut with a butter
knife
– Reactivity
• Some spontaneously react with oxygen like iron,
which flakes off
• Others react with oxygen to make a colorless tight
fitting oxide, such as chromium, thus protecting the
surface
• Some metals are inert to oxygen such as gold, silver
and platinum
Transition Metals
Ionic compound formation
– More than one oxidation state is often observed
– Cations, often are complexes
– Most compounds are colored, since complexes
absorb visible light
– Many compounds are paramagnetic
Transition elements on the periodic table
Dr.Monther F.Salem
Aqueous solutions containing metal ions
Co+2
Mn+2
Cr+3
Dr.Monther F.Salem
Fe+3
Ni+2
Dr.Monther F.Salem
Dr.Monther F.Salem
Colors of Representative Compounds of
the Period 4 Transition Metals
b
a
d
c
f
e
a = Scandium oxide
b = Titanium(IV) oxide
c = Vanadyl sulfate dihydrate
d = Sodium chromate
e = Manganese(II) chloride tetrahydrate
h
g
j
i
f = Potassium ferricyanide
g = Cobalt(II) chloride hexahydrate
h = Nickel(II) nitrate hexahydrate
i = Copper(II) sulfate pentahydrate
j = Zinc sulfate heptahydrate
Orbital Occupancy of the Period 4 Metals–I
Element
Sc
Partial Orbital Diagram
4s
3d
4p
Unpaired Electrons
1
Ti
2
V
3
Cr
6
Mn
5
Orbital Occupancy of the Period 4 Metals–II
Element
Fe
Partial Orbital Diagram
4s
3d
4p
Unpaired Electrons
4
Co
3
Ni
2
Cu
1
Zn
0
Reactivity:
Size of neutral atoms of d-block elements
gradually decreases
left to right across a row.
Due to increase in Zeff with increasing atomic #
Atomic radius increases going down a column.
Oxidation States
The common oxidation states for each element include +2, +3, or
both.
The first-row transition metals. The
most stable oxidation numbers are
shown in color. The zero oxidation
state is encountered in some
compounds, such as
Ni(CO)4 and Fe(CO)5.
Titanium bicycle
Dr.Monther F.Salem
General Trends among Transition Metals
Dr.Monther F.Salem
First-row Transition Metals
Scandium
– Rare element most always +3 oxidation state, ie
ScCl3, Sc2O3
– Chemistry of scandium resembles the lanthanides
First-row Transition Metals
Titanium
– Found in the earths crust (0.6%)
– Low density and high strength
– Fairly inert, and is used in pipes
– TiO2 is a very common white pigment
– Common oxidation state is +4
First-row Transition Metals
Vanadium
– Found in the earth’s crust about 0.02%
– Common oxidation state is +5
– Since vanadium contains d electrons solutions are
colored
First-row Transition Metals
Chromium
– Rare, but important industrial chemical
– Chromium oxide is colorless, tuff, and holds to the
metal strongly, almost in visible
– Chromium compounds in solution are also colored
since they contain d electrons
– Common oxidation states are +2, +3 and +6
First-row Transition Metals
• Iron
– Is the most abundant heavy metal (4.7%) in
earth’s crust,
– Common oxidation states +2 and +3
– Iron solutions are colored since they contain d
electrons
First-row Transition Metals
• Cobalt
– Relatively rare
– Hard bluish-white metal
– Common oxidation states are +2 and +3
First-row Transition Metals
• Nickel
– Most always the +2 oxidation state
– Sometimes +3 oxidation state
– Emerald green colored solutions
First-row Transition Metals
• Copper
– Quite common, as sulfides, chlorides and
carbonates
– Great electrical conductor second only to silver
– Widely used in plumbing
– Not highly reactive will not reduce H+
– Slowly oxides in air, producing a green oxide
– Common oxidation state +2, +1 is also known
– Aqueous solution are bright Royal blue
– Quite toxic, used to kill bacteria
– Paint often contains copper so algae do not grow on
the paint
First-row Transition Metals
Zinc
– Quite common in earths crust, usually as ZnS
– Great reducing agent, quite reactive
– Oxidation state of +2
– Used to galvanize steel
Coordination Compounds
• when a complex ion combines with counterions to
make a neutral compound it is called a
coordination compound
• the primary valence is the oxidation number of
the metal
• the secondary valence is the number of ligands
bonded to the metal
– coordination number
• coordination number range from 2 to 12, with the
most common being 6 and 4
CoCl36H2O = [Co(H2O)6]Cl3
Coordination Compound
Complex Ion Formation
• complex ion formation is a type of Lewis
acid-base reaction
• a bond that forms when the pair of electrons
is donated by one atom is called a
coordinate covalent bond
Ligands
• Atoms attached to a transition metal via coordinate
covalent bonds
• They are Lewis bases, since they donate a pair of
electrons to the transition metal.
• Ligands are classified relative to how many
attachments to the metal
– Monodentate forms one bond to a transition metal
– Lignads forming more than bond are called
chelating ligands, or chelates
Ligands
• Ligands are classified relative to how many
attachments to the metal
– Bidentate, a chelating agent, forms two
bonds, examples:
• Oxalate
• Ethylenediamine
– Polydentate forms more than two bonds.
• Diethylenetriamine
• Ethylenediaminetetraacetic acid
Ligands
• EDTA is used to remove lead from animals
• More complicated ligands are found in
biological compounds
• EDTA is used as a preservative to tie up
substances that could catalyze decomposition
of food products
Ligands with Extra Teeth
• some ligands can form more than one coordinate
covalent bond with the metal atom
– lone pairs on different atoms that are separate
enough so that both can reach the metal
• chelate is a complex ion containing a multidentate
ligand
– ligand is called the chelating agent
EDTA
a Polydentate Ligand
Complex Ions with Polydentate Ligands
Geometries in Complex Ions
Coordination Compounds
• The number of coordinate covalent bonds formed
by the metal ion and the ligands.
• Geometrical Common Shape
– Ligands = 2, then linear
– Ligands = 4, then tetrahedral, or square planar
– Ligands = 6, then octahedral and prismatic (rare)
Ligand
arrangements for
coordination
numbers 2, 4, and 6
Dr.Monther F.Salem