example: constructing a only mo diagram for iron...
TRANSCRIPT
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Example: Constructing a ‐only MO diagramfor Iron Pentacarbonyl, Fe(CO)5y , ( )5
D3h
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Example: Constructing a MO forIron Pentacarbonyl, Fe(CO)5y , ( )5
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Example: Constructing a MO forIron Pentacarbonyl, Fe(CO)5y , ( )5
Fe bonding AOsFe bonding AOs
A1‘ : 4s , 3dz2
E‘ : (4px , 4py ) (3dx2‐y2, 3dxy)
A2‘’ : (4pz)
Fe non‐bonding AOs
E‘’ : (3dxz, 3dyz)
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a2''
e'
a1' a1'
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Fe0 5CO
CO
FeOCCOCO
CO
4p (a2'', e')
a2''
4s (a1')
4p (a2 , e )
e'
3d (a1' , e', e'')a1'*
a1' a1'
a2''
e'
a1' 2a1'a1 , 2a1
a1'
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Fe0 5CO
CO
FeOCCOCO
CO
4p (a2'', e')
a2''
4s (a1')
p ( 2 , )2a1'*
e'
3d (a1' , e', e'')a1'*
a1' a1'
a2''
e'
a1', 2a1'a1 , 2a1
a1'2a1'
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Fe0 5CO
CO
FeOCCOCO
CO
4p (a2'', e')
a2''
4s (a1')
p ( 2 , )2a1'*
e'*
e'
3d (a1' , e', e'')a1'*
ea1' a1'
a2''
e'
a1', 2a1'e' a1 , 2a1
a1'
e
2a1'
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Fe0 5CO
CO
FeOCCOCO
CO
4p (a2'', e')
a2''*
a2''
4s (a1')
p ( 2 , )2a1'*
e'*
e'
3d (a1' , e', e'')a1'*
ea1' a1'
a2''
e'
a1', 2a1'
a2''
e' a1 , 2a1
a1'
e
2a1'
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Fe0 5CO
CO
FeOCCOCO
CO
4p (a2'', e')
a2''*
e'* a2''
4s (a1')
p ( 2 , )2a1'*
e'*
e'
3d (a1' , e', e'')e''
a1'*
ea1' a1'
a2''
e'
a1', 2a1'
a2''
e' a1 , 2a1
a1'
e
2a1'
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Fe0 5CO
CO
FeOCCOCO
CO
4p (a2'', e')
a2''*
e'* a2''
4s (a1')
4p (a2 , e )2a1'*
e'*
e'
3d (a1' , e', e'')e''
a1'*
ea1' a1'
a2''
e'
a1' 2a1'
a2''
e' a1 , 2a1
a1'
e
2a1'
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Fe0 5CO
CO
FeOCCOCO
CO
4p (a2'', e')
a2''*
e'* a2''
LUMO
4s (a1')
p ( 2 , )2a1'*
e'*
e'
HOMO
LUMO
3d (a1' , e', e'')e''
a1'*
ea1' a1'
HOMO
a2''
e'
a1', 2a1'
a2''
e' a1 , 2a1
a1'
e
2a1'
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Fe0 5CO
CO
FeOCCOCO
CO
4p (a2'', e')
a2''*
e'* a2''
4s (a1')
p ( 2 , )2a1'*
e'*
e'
3d (a1' , e', e'')e''
a1'*
ea1' a1'
a2''
e'
a1', 2a1'
a2''
e' a1 , 2a1
a1'
e
2a1'
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a2''
e'
a1' a1'
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Construction of MO diagrams for Transition Metal Complexes
bonding complexes
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Example: Constructing a MO forChromium Hexacarbonyl, Cr(CO)6y , ( )6
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Example: Constructing a MO forChromium Hexacarbonyl, Cr(CO)6y , ( )6
Oh E 8C3 6C2 6C4 3C2 i 6S4 8S6 3 h 6 d /h
h = 48
h 3 2 4 2 4 6 h d
12 0 0 0 -4 0 0 0 0 0
A1 12 0 0 0 -12 0 0 0 0 0 0 0A1g 12 0 0 0 -12 0 0 0 0 0 0 0A2g 12 0 0 0 -12 0 0 0 0 0 0 0Eg 24 0 0 0 -24 0 0 0 0 0 0 0T1g 36 0 0 0 12 0 0 0 0 0 48 1T2g 36 0 0 0 12 0 0 0 0 0 48 1A1u 12 0 0 0 -12 0 0 0 0 0 0 0A2u 12 0 0 0 -12 0 0 0 0 0 0 0Eu 24 0 0 0 -24 0 0 0 0 0 0 0uT1u 36 0 0 0 12 0 0 0 12 0 48 1T2u 36 0 0 0 12 0 0 0 12 0 48 1
d
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Example: Constructing a MO forChromium Hexacarbonyl, Cr(CO)6y , ( )6
• Cr ‐bonding AOs
T2g : (3dxy, 3dxz, 3dyz)
T1u : (4px , 4py , 4pz)
• T2g previously considered non‐bonding in ‐bondingschemescheme
• T1u combines with T1u SALC in in ‐bonding scheme
• T1g , T2u ‐SALCs are non‐bonding
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• T AOs overlap more effectively with T SALC thus the bonding interaction is• T1u AOs overlap more effectively with T1u ‐SALC thus the ‐bonding interaction isconsidered negligible or at most only weakly‐bonding.
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dx2-y2dz2
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T2g3 x
dx2-y2dz2
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T2g3 x
dx2-y2dz2
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T2g3 x
dx2-y2dz2
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T2g3 x
LUMO
O
dx2-y2dz2 HOMO
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Dewar‐Chatt‐Duncanson model
v(CO) cm‐1
[Ti(CO)6]2‐ 1748
[V(CO)6]‐ 1859
( )Cr(CO)6 2000
[Mn(CO)6 ]+ 2100
[Fe(CO)6 ]2+ 2204[Fe(CO)6 ] 2204
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Summary of ‐bonding in Oh complexes
donor ligands result in L→M bonding, a smaller o favoring high spinconfigurations and a decreased stability.
acceptor ligands result in M→L bonding, a larger ofavoring low spin configurations with an increasedstability.
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Example: Constructing MOs for Titanium Tetraisopropoxide, Ti(OiPr)4p p , ( )4
O
TiO O
O
OiPr
TiiPrO OiP
OiPrO
point group = Td
OiPr
z
x
y
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Example: Constructing MOs for Titanium Tetraisopropoxide, Ti(OiPr)4p p , ( )4
OiPr
h = 24
TiiPrO OiPr
OiPr
Td E 8C3 3C2 6S4 6 d /h
8 -1 0 0 0
point group = Td
z
A1 8 -8 0 0 0 0 0A2 8 -8 0 0 0 0 0E 16 8 0 0 0 24 1
x
E 16 8 0 0 0 24 1T1 24 0 0 0 0 24 1T2 24 0 0 0 0 24 1
y
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Example: Constructing MOs for Titanium Tetraisopropoxide, Ti(OiPr)4p p , ( )4
Th OiP SALC i d f fill d d bit l th O t• The OiPr SALCs are comprised of filled px and py orbitals on the O atoms.
• Ti bonding AOs
E : (3dz2, 3dx2‐y2) E : (3dz , 3dx y )
T2 : (4px , 4py , 4pz)
(3dxy, 3dxz, 3dyz)
• The T1 SALC is non‐bonding.
• Significant overlap occurs between the E SALC and the e AOs on Ti (3dz2, 3dx2‐y2)
• As the 4p AOs on Ti (t2) are primarily involved in ‐bonding we will assume that they have negligible ‐interaction here.
[It is very likely that there is extensive d‐pmixing involved in this system.]
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Ti+4 4 OiPr
OiPr
TiiPrO OiPr
OiPr
4p (t2)
t2*
a1*
4s (a1) t2*
3d (t2 , e)
e, t1 , t2e
a1
t2
t
dx2-y2dz2
a1
t2
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Ti+4 4 OiPr
OiPr
TiiPrO OiPr
OiPr
4p (t2)
t2*
a1*
4s (a1) t2*
3d (t2 , e)
e, t1 , t2e
a1
t2
t
dx2-y2dz2
a1
t2
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Ti+4 4 OiPr
OiPr
TiiPrO OiPr
OiPr
4p (t2)
t2*
a1*
4s (a1)
e*
t2*
3d (t2 , e)
e, t1 , t2
a1
t2
t
e
dx2-y2dz2
a1
t2
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Ti+4 4 OiPr
OiPr
TiiPrO OiPr
OiPr
4p (t2)
*
t2*
a1*
4s (a1)
e*
t2
3d (t2 , e)
e, t1 , t2
a1
t2
t
e
t2
dx2-y2dz2
a1
t2
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Ti+4 4 OiPr
OiPr
TiiPrO OiPr
OiPr
4p (t2)
*
t2*
a1*
4s (a1)
e*
t2
3d (t2 , e)
e, t1 , t2t1
a1
t2
t
e
t2
dx2-y2dz2
a1
t2
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Ti+4 4 OiPr
OiPr
TiiPrO OiPr
OiPr
4p (t2)
*
t2*
a1*
4s (a1)
e*
t2
3d (t2 , e)
e, t1 , t2t1
a1
t2
t
e
t2
a1
t2
dx2-y2dz2