HYBRIDIZATION IN SQUARE HYBRIDIZATION IN SQUARE PLANER COMPLEXSPLANER COMPLEXS

TOPIC:-HYBRIDIZATION IN SQUARE TOPIC:-HYBRIDIZATION IN SQUARE PLANER COMPLEX.PLANER COMPLEX.COURES :-COURES :-M.Sc(Hons)CHEMISTRM.Sc(Hons)CHEMISTR

ABSTRACTABSTRACTHYBERDIZATIONHYBERDIZATION:-:-The phenomenon of mixing of The phenomenon of mixing of orbitals of the same atom with slight difference in energies so orbitals of the same atom with slight difference in energies so as to redistribute their energies and give new orbitals of as to redistribute their energies and give new orbitals of equivalent energy and shape. The new orbitals which get equivalent energy and shape. The new orbitals which get formed areformed are known as hybrid. known as hybrid.TYPES OF HYBERDIZATION:-These are:-TYPES OF HYBERDIZATION:-These are:-SP HYBERDIZATION SP HYBERDIZATION SP2 HYBERDIZATION SP2 HYBERDIZATION SP3 HYBERDIZATION (Regular tetrahedron geometry)SP3 HYBERDIZATION (Regular tetrahedron geometry)SP3D HYBERDIZATION (Trigonal bipyramidal geometry )SP3D HYBERDIZATION (Trigonal bipyramidal geometry )SP3D2 HYBERDIZATION (Octahedral geometry )SP3D2 HYBERDIZATION (Octahedral geometry )SP3D3 HYBERDIZATION (Pentagonal bipyramedal geometry SP3D3 HYBERDIZATION (Pentagonal bipyramedal geometry DSP2 HYBERDIZATION (Square planer geometry )DSP2 HYBERDIZATION (Square planer geometry )

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 — magnetismMolecular Spectroscopy — Electronic Spectroscopy — Vibrational/Rotational Spectroscopies — Nuclear Magnetic Resonance (NMR) Spectroscopy

INTRODUCTION

Hybridization and the LE Model of Bonding

— Assume bonding involves only valence orbitals— Methane, CH4:

Isolated atomsIsolated atoms Valence orbitalsValence orbitals

HH 1s1s11

CC 2s2s222p2p2 2 (2p: 2p(2p: 2pxx, 2p, 2pyy, 2p, 2pzz))

H atoms in CH4 will use 1s orbitalsOf 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.

C

H

H H

H

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

Energy hybridization

Orbitals in C in CH4 molecule

2p

2ssp3

Orbitals in isolated C atom

Native 2Native 2ss and three and three 2p2p atomic orbitals atomic orbitals characteristic of a free carbon atom are combined characteristic of a free carbon atom are combined

to to

form a new set of four sform a new set of four spp3 orbitals3 orbitals..

Energy-level diagram showing Energy-level diagram showing the formation of four the formation of four spsp33 orbitals orbitals

Consider ethylene C2H4 molecule Lewis structure

— 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

120o angles• VSEPR model predicts a trigonal planar geometry

• sp3 orbitals with tetrahedral geometry and 109.5o angles will not work here.

Sp2 Hybridization

C C

H

HH

H

The plastics shown here were The plastics shown here were manufactured with ethylene.manufactured with ethylene.

The hybridization of the The hybridization of the ss, , ppxx, and , and

ppyy atomic orbitals results in the formation of three atomic orbitals results in the formation of three

spsp22 orbitals centered in the orbitals centered in the xyxy plane. plane.

1 2s orbital +2 2p (px, py) orbitals

3 sp2 orbitals

Energy-level diagram of sp2 hybridization

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.

Energy hybridization

C atom orbitals in ethylene

2p

2ssp2

Orbitals in isolated C atom

E 2p

When one s and two When one s and two pp oribitals are mixed to form a oribitals are mixed to form a set of three set of three spsp22 orbitals, one p orbital remains orbitals, one p orbital remains

unchanged and unchanged and is perpendicular to the plane of the hybrid orbitals.is perpendicular to the plane of the hybrid orbitals.

The The sigmasigma bonds in ethylene. bonds in ethylene.

A carbon-carbon double bond consists of a A carbon-carbon double bond consists of a sigma bond and a pi bond.sigma bond and a pi bond.

(a) The orbitals used to form the bonds in (a) The orbitals used to form the bonds in ethylene. (b) The Lewis structure for ethylene. (b) The Lewis structure for

ethylene.ethylene.

An atom surrounded by 3 effective electron pairs uses sp2 hybridized orbitals for bonding.

Example

H2CO formaldehyde

Lewis Structure

— 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.

Other sp2 hybridized carbon atoms

C O

H

H

....

sp Hybridization

Carbon in carbon dioxide, CO2 uses another type of hybridization (rather than sp2 or sp3)

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

O=C=O‧‧‧‧‧‧

‧‧

Ene

rgy

2p

1s

2psp

Hybridization

Orbitals in a free C atom

Orbitals in sp hybridized orbitals in CO2

When one s orbital and one When one s orbital and one pp orbital are hybridized, a set of two orbital are hybridized, a set of two spsp orbitals oriented at 180 degrees results.orbitals oriented at 180 degrees results.

The hybrid orbitals in the The hybrid orbitals in the COCO22 molecule molecule

(a) Orbitals predicted by the LE model to (a) Orbitals predicted by the LE model to describe (b) The Lewis structure for carbon describe (b) The Lewis structure for carbon

dioxidedioxide

Other Examples of sp Hybridization

Example

N2 molecule

N atom: 2s22p3

Lewis Structure

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.

： N N：

(a) An sp hybridized nitrogen atom (a) An sp hybridized nitrogen atom (b) The s bond in the N(b) The s bond in the N22 molecule (c) the two p molecule (c) the two p

bonds bonds in Nin N22 are formed when are formed when

dsp3 Hybridization

Consider the bonding in phosphorous pentachloride PCl5

Lewis structure(assuming d-orbital participation)

– 40 valence electrons in the molecule – 5 electron pairs around the central atom P ． VSEPR predicts trigonal bipyramidal geometry

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 pairsIn general, when there are 5 effective pairs around an atom it uses dsp3 orbitals.

– one 3d orbital one 3s orbital three 3p orbital

：

：

P

Cl

Cl

Cl

Cl

Cl

：： ：

：：

：

：： ：

：：

： ：

A set of A set of dspdsp33 hybrid orbitals hybrid orbitals on a phosphorous atomon a phosphorous atom

The orbitals used to form the The orbitals used to form the bonds in the PClbonds in the PCl55 molecule molecule

Other Examples of dsp3 Hybridization

Triiodide ion I3-

Lewis structure

Arsenic pentafluoride AsF5

d2sp3 hybridization

Sulfur hexafluoride, SF6

– 48 valence electrons– 6 effective pairs around S atoms– VSEPR model predicts Octahedral geometry The 6 pairs lead to d2sp3 hybridization of s atom, forming a set of 6 octahedrally oriented d2sp3 orbitals.

As

F

F

F

F

F

：

：：：

：

：：

：

：： ：

：：

： ：

[ I – I – I ]-：：

：

：：：

：：

：

：

：：

S

F

F

F

FF

F

：

：

：

：

：：

：

：

：

：

：

：

：

：

An octahedral set of dAn octahedral set of d22spsp33 orbitals on a sulfur atomorbitals on a sulfur atom

The relationship among the number The relationship among the number of effective pairs, their spatial arrangement, of effective pairs, their spatial arrangement,

and the hybrid orbital set requiredand the hybrid orbital set required

The relationship among the number The relationship among the number of effective pairs, their spatial arrangement, of effective pairs, their spatial arrangement, and the hybrid orbital set required and the hybrid orbital set required (cont’d)(cont’d)

Turning to Square Planar Turning to Square Planar ComplexesComplexes

y

x

zMost convenient to use a local coordinate system on each ligand with

y pointing in towards the metal. py to be used for bonding.

z being perpendicular to the molecular plane. pz to be used for bonding perpendicular to the plane, .

x lying in the molecular plane. px to be used for bonding in the molecular plane, |.

ML4 square planar complexes

ligand group orbitals and matching metal orbitals

ML4 square planar complexesMO diagram

-only bonding - bonding

SQUARE PLANER MOLECULE SQUARE PLANER MOLECULE GEOMETRYGEOMETRY

•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 STRUCTURE OF SQUARE PLANER MOLECULEPLANER MOLECULE

Molecular Geometry

bond length, angle determined experimentallyLewis structures bonding

geometryVSEPR

Valence Shell Electron Pair Repulsion

octahedron 90o bond angles

trigonal bipyramid equatorial 120o

axial 180o

big groupssmall groups

tetrahedron 109.5o

trigonal planar 120o

linear 180o

geometry apply to Chemistry

linear 180o

BeCl2

valence e- = 2 + (2 x 7) = 16e-

Cl....

..BeCl....

..

fewer than 8e-

valence pairs on Be bonding e-

linear molecule

two

linear 180o

CO2

valence e- = 4 + (2 x 6) = 16e-

CO....

.. O....

.. CO..

O..

.. ..

valence pairs on C ignore double bondstwo

single and double bonds same

linearmolecular shapemolecular geometry linear

trigonal planar 120o

SO2

valence e- = 6+ (2 x 6) = 18e-

valence pairs on Sthree

one lone pairmolecular geometry

molecular shape bent

trigonal

S O....

..O....

:

SO....

.. O....

..:

SO...... O

..

..

:

two bonding pairs

< 120o

tetrahedral 109.5o

CH4

valence e- = 4+(4 x 1) = 8e-

valence pairs on Cfour C HH

H

H109.5o

molecular geometry

molecular shape tetrahedral

tetrahedral

tetrahedral 109.5o

NH3

valence e- = 5+ (3 x 1) = 8e-

valence pairs on Nfour N HH

H

:

< 109.5o

molecular geometry

molecular shape trigonal pyramid

tetrahedral

one lone pairthree bonding pairs

tetrahedral 109.5o

H2O

valence e- = 6+ (2 x 1) = 8e-

valence pairs on OfourO HH

::

< 109.5o

molecular geometry

molecular shape bent

tetrahedral

two lone pairtwo bonding pairs

bipyramidal 120o and 1800

PCl5

valence e- = 5+ (5 x 7) = 40e-

valence pairs on Pfive

molecular geometry

molecular shape bipyramidal

bipyramidal

P

Cl....

..

Cl....

..

Cl....

..Cl....

..

Cl

......

90o

120o

180o

bipyramidal 120o and 1800

SF4

valence e- = 6+ (4 x 7) = 34e-

valence pairs on Sfive

molecular geometry

molecular shape seesaw

bipyramidal

one lone pair

four bonding pairs S..F..

..

..F..

..

..F..

....F..

..

:

< 180o

bipyramidal 120o and 1800

ClF3

valence e- = 7+ (3 x 7) = 28e-

valence pairs on Clfive

molecular geometry

molecular shape T

bipyramidal

two lone pair

three bonding pairsCl

..F..

..

..F..

..

..F..

..

::

180o90o

bipyramidal 120o and 1800

ICl2-

valence e- = 7+ (2 x 7) + e-

valence pairs on Ifive

molecular geometry

molecular shape linear

bipyramidal

three lone pair on I

two bonding pairs

= 22e-

I..Cl..

..

::

..Cl..

..

:

octahedral 90o

BrF5

valence e- = 7+ (5 x 7)

valence pairs on Brsix

molecular geometry

molecular shape square pyramidal

octahedral

= 42e-

one lone pair

five bonding pairs

BrF....

..F....

..

F....

..

F....

..

F.... ..:

octahedral 90o

XeF4

valence e- = 8+ (4 x 7)

valence pairs on Xesix

molecular geometry

molecular shape square planar

octahedral

= 36e-

two lone pair

four bonding pairsXe

F....

..F....

..

F....

..

F....

..

:

:

SUBSTITUTION IN SQUARE PLANERSUBSTITUTION IN SQUARE PLANER

Substitution at Square Planar Metal ComplexesSubstitution at Square Planar Metal Complexes Examples of Square Planar Transition Metal Examples of Square Planar Transition Metal Complexes:Complexes: Ni(II)Ni(II) (mainly d8) (mainly d8) Rh(I) Pd(II)Rh(I) Pd(II) Ir(I) Pt(II) Au(III)Ir(I) Pt(II) Au(III) General Rate Law:General Rate Law: Factors Which Affect The Rate Of SubstitutionFactors Which Affect The Rate Of Substitution 1.1. Role of the Entering Group Role of the Entering Group 2.2. The Role of The Leaving Group The Role of The Leaving Group 3.3. The Nature of the Other Ligands in the Complex The Nature of the Other Ligands in the Complex 4.4. Effect of the Metal Centre Effect of the Metal Centre

SUBSTITUTION IN SQUARE PLANERSUBSTITUTION IN SQUARE PLANER

GRAPH OF SQUARE PLANER GRAPH OF SQUARE PLANER SUBSTITUTIONSUBSTITUTION

REFERENCEREFERENCE^ G. L. Miessler and G. L. Miessler and

D. A. Tarr. D. A. Tarr. Inorganic Inorganic ChemistryChemistry, 3rd Ed., , 3rd Ed., Pearson/Prentice Pearson/Prentice

Hall..Hall..Miessler and Miessler and

Tarr(inorgnic Tarr(inorgnic chemistry)chemistry)

THE ENDTHE END

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