Transcript Sp 2 Hybridization

HYBRIDIZATION IN SQUARE
PLANER COMPLEXS
TOPIC:-HYBRIDIZATION IN SQUARE
PLANER COMPLEX.
COURES
:-M.Sc(Hons)CHEMISTR
ABSTRACT
HYBERDIZATION:-The phenomenon of mixing of
orbitals of the same atom with slight difference in energies so
as to redistribute their energies and give new orbitals of
equivalent energy and shape. The new orbitals which get
formed are known as hybrid.
TYPES OF HYBERDIZATION:-These are:SP HYBERDIZATION
SP2 HYBERDIZATION
SP3 HYBERDIZATION (Regular tetrahedron geometry)
SP3D HYBERDIZATION (Trigonal bipyramidal geometry )
SP3D2 HYBERDIZATION (Octahedral geometry )
SP3D3 HYBERDIZATION (Pentagonal bipyramedal geometry
DSP2 HYBERDIZATION (Square planer geometry )
INTRODUCTION
Hybridization and the LE Model of Bonding
— Lewis structures of molecules
— prediction of geometry of molecules
— hybrid orbitals (sp3, sp2, sp, dsp3, d2sp3)
— interpretation of structure and bonding
Molecular Orbital Model of Bonding in Molecules
— molecular orbital diagrams
— bond order
— magnetism
Molecular Spectroscopy
Spectroscopy
— Vibrational/Rotational Spectroscopies
— Electronic
— Nuclear
Magnetic Resonance (NMR) Spectroscopy
Hybridization and the LE Model of Bonding
— Assume bonding involves only valence orbitals
H
— Methane, CH4:
H
C
H
H
Isolated atoms
Valence orbitals
H
1s1
C
2s22p2 (2p: 2px, 2py,
2pz)
H atoms in CH4 will use 1s orbitals
Of the two types of orbitals (2s and 2p)
Which will C atoms use for bonding in CH4?
— If both are used: 2 different types of C-H bonds
(Contrary to experimental facts)
— Neither of the “native” atomic orbitals
of C atoms are used; instead, new hybrid orbitals are used.
Hybridization of atomic orbitals
The mixing of the “native” atomic orbitals to form
special orbitals for bonding is called hybridization.
The 4 new equivalent orbitals formed by mixing the
one 2s and three 2p orbitals are called sp3 orbitals.
The carbon atom is said to undergo sp3 hybridization,
i.e. is sp3 hybridized.
Energy-level diagram showing the sp3 hybridization
2p hybridization
Energy
sp3
2s
Orbitals in isolated
C atom
Orbitals in C in
CH4 molecule
Native 2s and three 2p atomic orbitals
characteristic of a free carbon atom are combined
to
form a new set of four sp3 orbitals.
Energy-level diagram showing
the formation of four sp3 orbitals
Sp2 Hybridization
Consider ethylene C2H4 molecule
H
H
C
H
Lewis structure
C
H
— 12 valence e-s in the molecule
— What orbitals do the carbon atoms use to bond in ethylene?
— 3 effective electron pairs around each carbon
• VSEPR model predicts a trigonal planar
geometry
120o angles
• sp3 orbitals with tetrahedral geometry and
109.5o angles will not work here.
The plastics shown here were
manufactured with ethylene.
The hybridization of the s, px, and
py atomic orbitals results in the formation of three
sp2 orbitals centered in the xy plane.
1 2s orbital
+
2 2p (px, py) orbitals
3 sp2 orbitals
Energy-level diagram of sp2 hybridization
2p hybridization
Energy
2s
Orbitals in isolated
C atom
E
2p
sp2
C atom orbitals
in ethylene
Un-hybridized pz orbital
Carbon uses the sp2 hybridized orbitals for forming sigmal (σ)
bonds within the plane
The remaining 2pz orbital is used for forming the pi (π) bond.
Note that the double bond consists of one σ and one π bond.
When one s and two p oribitals are mixed to form a
set of three sp2 orbitals, one p orbital remains
unchanged and
is perpendicular to the plane of the hybrid orbitals.
The sigma bonds in ethylene.
A carbon-carbon double bond consists of a
sigma bond and a pi bond.
(a) The orbitals used to form the bonds in
ethylene. (b) The Lewis structure for
ethylene.
Other sp2 hybridized carbon atoms
An atom surrounded by 3 effective electron pairs
uses sp2 hybridized orbitals for bonding.
Example
H2CO formaldehyde
H
C
..
O..
Lewis Structure
H
— 12 valence electrons
— 3 effective pairs around C
Sp2 hybridized orbitals are used to form the C-H bonds
and the C-O σ bond, the un-hybridized 2pz orbital is used
to form the C=O π bond.
sp Hybridization
Carbon in carbon dioxide, CO2 uses another type of hybridization
(rather than sp2 or sp3)
O=C=O
2 hybrid orbitals required to meet the 180° (linear) geometry
requirement are sp orbitals.
2 effective pairs around C atom
sp hybrid orbitals
3 effective pairs around O atom
sp2 orbitals
Energy
2p
1s
Orbitals in a
free C atom
Hybridization
2p
sp
Orbitals in sp hybridized
orbitals in CO2
When one s orbital and one
p orbital are hybridized, a set of two sp
orbitals oriented at 180 degrees results.
The hybrid orbitals in the
CO2 molecule
(a) Orbitals predicted by the LE model to
describe (b) The Lewis structure for carbon
dioxide
Other Examples of sp Hybridization
Example
N2 molecule
：N
N：
Lewis Structure
N atom: 2s22p3
2 effective pairs around each N atom in the Lewis structure
– Linear (180°) geometry
– 2 sp orbitals for each N atom:
．1 sp orbital for forming the σ bond
．1 sp orbital for holding the lone pair
The remaining un-changed 2p orbitals are used to form
the 2 π bonds.
Each triple bond consists of one σ and two π bonds.
(a) An sp hybridized nitrogen atom
(b) The s bond in the N2 molecule (c) the two p
bonds
in N2 are formed when
dsp3 Hybridization
Consider the bonding in phosphorous pentachloride PCl5
Cl：
：Cl
Cl
P
Lewis structure
(assuming d-orbital participation)
： ：：
： ：：
：Cl
Cl：
– 40 valence electrons in the molecule
– 5 electron pairs around the central atom P
．VSEPR predicts trigonal bipyramidal geometry
– one 3d orbital
one 3s orbital
three 3p orbital
a set of 5 dsp3 hybrid orbitals
oriented in a trigonal bipyramidal
configuration
– the Cl atoms in PCl5 use sp3 orbitals to form the P-Cl bonds and
to hold the lone pairs
In general, when there are 5 effective pairs around an atom
it uses dsp3 orbitals.
A set of dsp3 hybrid orbitals
on a phosphorous atom
The orbitals used to form the
bonds in the PCl5 molecule
Other Examples of dsp3 Hybridization
： ：
：
： ：
Triiodide ion I3-
Lewis structure
：
[：I – I – I：]-
F：
：F
F
As
： ：：
Arsenic pentafluoride
AsF5
： ：：
：F
F：
：F：
：
：F：
The 6 pairs lead to d2sp3 hybridization of s atom,
forming a set of 6 octahedrally oriented d2sp3 orbitals.
：F：
：：
S
：
：F：
：F：
：
– 48 valence electrons
– 6 effective pairs around S atoms
– VSEPR model predicts Octahedral geometry
：
Sulfur hexafluoride, SF6
：
d2sp3 hybridization
F：
An octahedral set of d2sp3
orbitals on a sulfur atom
The relationship among the number
of effective pairs, their spatial arrangement,
and the hybrid orbital set required
The relationship among the number
of effective pairs, their spatial arrangement,
and the hybrid orbital set required (cont’d)
Turning to Square Planar
Complexes
z
y
x
Most convenient to use a local coordinate
system on each ligand with
y pointing in towards the metal. py to be used
for s bonding.
z being perpendicular to the molecular plane. pz
to be used for p bonding perpendicular to the
plane, p^.
x lying in the molecular plane. px to be used
for p bonding in the molecular plane, p|.
ML4 square planar complexes
ligand group orbitals and matching metal orbitals
ML4 square planar complexes
MO diagram
s-only bonding
- bonding
SQUARE PLANER MOLECULE
GEOMETRY
•Idealized structure of a compound with square planar
coordination geometry.
•The square planar molecular geometry in chemistry describes
the stereochemistry (spatial arrangement of atoms) that is adopted
by certain chemical compounds .As the name suggests, molecules
of this geometry have their atoms positioned at the corners of a
square on the same plane about a central atom.
STRUCTURE OF SQUARE
PLANER MOLECULE
Molecular Geometry
bond length, angle determined experimentally
Lewis structures bonding
geometry
VSEPR
Valence Shell Electron Pair Repulsion
octahedron 90o bond angles
small groups
big groups
trigonal bipyramid equatorial 120o
axial
180o
tetrahedron
109.5o
trigonal planar 120o
linear
180o
geometry apply to Chemistry
linear
180o
BeCl2
valence e- = 2 + (2 x 7) = 16efewer than 8eBe
..
Cl
..
..
..
..
Cl
..
two valence pairs on Be
bonding elinear molecule
linear
180o
CO2
valence e- = 4 + (2 x 6) = 16e-
..
C O
..
..
..
..
O
..
..
O
..
..
C O
..
two valence pairs on C ignore double bonds
single and double bonds same
molecular geometry linear
molecular shape
linear
trigonal planar 120o
SO2
three valence pairs on S
two bonding pairs
one lone pair
S
..
O
..
..
S O
..
:
..
O
..
..
:
..
O
..
..
S
..
O
..
..
..
..
O
..
:
valence e- = 6+ (2 x 6) = 18e-
molecular geometry trigonal
molecular shape bent
< 120o
tetrahedral
109.5o
CH4
valence e- = 4+(4 x 1) = 8eH
four valence pairs on C
109.5o
H
C
H
H
molecular geometry tetrahedral
molecular shape
tetrahedral
tetrahedral
109.5o
NH3
valence e- = 5+ (3 x 1) = 8e-
:
four valence pairs on N
three bonding pairs
one lone pair
H
N
H
H
molecular geometry tetrahedral
molecular shape trigonal pyramid
< 109.5o
tetrahedral
109.5o
H2O
four valence pairs on O
two bonding pairs
two lone pair
:
valence e- = 6+ (2 x 1) = 8eH
O
H
:
molecular geometry tetrahedral
molecular shape bent
< 109.5o
bipyramidal 120o and 1800
PCl5
..
P
..
120o
..
five valence pairs on P
180o
90o
..
Cl
..
..
Cl
..
..
..
..
Cl
..
..
Cl
..
Cl
..
..
valence e- = 5+ (5 x 7) = 40e-
molecular geometry bipyramidal
molecular shape bipyramidal
bipyramidal 120o and 1800
SF4
valence e- = 6+ (4 x 7) = 34e-
:
..
.. ..
..
..
..
five valence pairs on S
F
S F
..
..
four bonding pairs
..
..
F
F
..
one lone pair
..
< 180o
molecular geometry bipyramidal
molecular shape seesaw
bipyramidal 120o and 1800
ClF3
valence e- = 7+ (3 x 7) = 28e-
:
180o
.. ..
90o
..
five valence pairs on Cl
three bonding pairs
two lone pair
..
..
F
.. Cl ..F..
F
..
molecular geometry bipyramidal
molecular shape T
bipyramidal 120o and 1800
ICl2valence e- = 7+ (2 x 7) + e- = 22e-
:
I
..
Cl
..
..
..
five valence pairs on I
two bonding pairs
three lone pair on I
..
Cl
..
molecular geometry bipyramidal
molecular shape linear
octahedral
90o
BrF5
Br
..
..
..
F
..
..
six valence pairs on Br
five bonding pairs
one lone pair
..
F
..
..
F
..
..
..
..
F
..
..
F
..
:
valence e- = 7+ (5 x 7) = 42e-
molecular geometry octahedral
molecular shape square pyramidal
octahedral
90o
XeF4
:
..
..
six valence pairs on Xe
four bonding pairs
two lone pair
..
F
..
Xe ..
F
..
..
..
..
F
..
..
F
..
:
valence e- = 8+ (4 x 7) = 36e-
molecular geometry octahedral
molecular shape square planar
SUBSTITUTION IN SQUARE PLANER
Substitution at Square Planar Metal Complexes
Examples of Square Planar Transition Metal
Complexes:
Ni(II) (mainly d8) Rh(I) Pd(II) Ir(I) Pt(II) Au(III)
General Rate Law:
Factors Which Affect The Rate Of Substitution
1. Role of the Entering Group
2. The Role of The Leaving Group
3. The Nature of the Other Ligands in the Complex
4. Effect of the Metal Centre
SUBSTITUTION IN SQUARE PLANER
GRAPH OF SQUARE PLANER
SUBSTITUTION
REFERENCE
^ G. L. Miessler and
D. A. Tarr. Inorganic
Chemistry, 3rd Ed.,
Pearson/Prentice
Hall..
Miessler and
Tarr(inorgnic
chemistry)
THE END
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