Download Chemistry of the d

Chemistry of the
d-Block Elements
History:
Louis Nicolas Vauquelin
16. Mai 1763 – 14. Nov. 1829
Leopold Gmelin
2. Aug. 1788 – 13. Apr. 1853
Chemistry of the
d-Block Elements
History:
NH3
H3N
Pd
H3 N
Cl
Cl
Pd
NH3
Cl
Cl
Louis Nicolas Vauquelin
1813
CN
CN
NC
III
Co
Gmelin
1822
CN
NC
NC
1
Chemistry of the
d-Block Elements
History:
1844: Peyrone’s Chloride
[PtCl2(NH3)2]
-- note! same formula! --
1844: Reiset
[PtCl2(NH3)2] !
(isomers are super-important in chemistry!)
Chemistry of the
d-Block Elements
cis- and trans- Platinum Isomers: Serendipity in Chemistry
Cisplatin was approved by the
FDA for the treatment of
genitourinary tumors in 1978.
Prof. Barnett Rosenberg, MSU
(Prof. S.J. Lippard, MIT)
"Testicular cancer went from a disease that normally killed about
80% of the patients, to one which is close to 95% curable. This is
probably the most exciting development in the treatment of
cancers that we have had in the past 20 years. It is now the
treatment of first choice in ovarian, bladder, and osteogenic
sarcoma [bone] cancers as well."
—Barnett Rosenberg, who led the research group that discovered
cisplatin, commenting on the impact of cisplatin in cancer
chemotherapy
Since then, Michigan State has
collected over $160 million in
royalties from cisplatin and a
related drug, carboplatin, which
was approved by the FDA in 1989
for the treatment of ovarian
cancers.
Newest generation:
O
NH 3
O
Pt
O
NH 3
O carboplatin
2
Chemistry of the
d-Block Elements
Cisplatin acts by cross-linking DNA in several different ways, making it impossible for rapidly dividing cells to
duplicate their DNA for mitosis. The damaged DNA sets off DNA repair mechanisms, which activate apoptosis
when repair proves impossible. The trans-isomer does not have this pharmacological effect.
B. Rosenberg et al. in Nature 1965, 205, 698
Stephen J. Lippard et al. in Nature (1999), 399, 708 - 712
Basis for recognition of cisplatin-modified DNA by high-mobility-group proteins
Barnett Rosenberg, MSU (1926 - )
SUMMARY: The anticancer activity of cis -diamminedichloroplatinum(II) (cisplatin)
arises from its ability to damage DNA, with the major adducts formed being intrastrand
d(GpG) and d(ApG)
Chemistry of the
d-Block Elements
Cisplatin acts by crosslinking DNA in several different ways, making it impossible for rapidly dividing cells to
duplicate their DNA for mitosis. The damaged DNA sets off DNA repair mechanisms, which activate apoptosis
when repair proves impossible. The trans isomer does not have this pharmacological effect.
B. Rosenberg et al. in Nature 1965, 205, 698
Stephen J. Lippard et al. in Nature (1999), 399, 708 - 712
Basis for recognition of cisplatin-modified DNA by high-mobility-group proteins
Stephen J. Lippard, MIT (??? - )
SUMMARY: The anticancer activity of cis -diamminedichloroplatinum(II) (cisplatin)
arises from its ability to damage DNA, with the major adducts formed being intrastrand
d(GpG) and d(ApG)
3
Chemistry of the
d-Block Elements
Cisplatin acts by crosslinking DNA in several different ways, making it impossible for rapidly dividing cells to
duplicate their DNA for mitosis. The damaged DNA sets off DNA repair mechanisms, which activate apoptosis
when repair proves impossible. The trans isomer does not have this pharmacological effect.
B. Rosenberg et al. in Nature 1965, 205, 698
Stephen J. Lippard et al. in Nature (1999), 399, 708 - 712
Basis for recognition of cisplatin-modified DNA by high-mobility-group proteins
SUMMARY: The anticancer activity of cis -diamminedichloroplatinum(II) (cisplatin)
arises from its ability to damage DNA, with the major adducts formed being intrastrand
d(GpG) and d(ApG)
Chemistry of the
d-Block Elements
Another success story at the HEART of coordination chemistry:
CardioLite
"Davison realized that fundamental coordination chemistry
would shed light on the chemical characteristics of the element
technetium and that these basic chemical characteristics could be
translated into the rational design of new radiopharmaceuticals,"
Orvig notes in the article. He calls Davison
"one of the fathers of medicinal inorganic chemistry.“
Prof. Chris Orvig, University of British Columbia
taken from SNM advancing molecular imaging
Alan Davison, MIT (??? - )
4
Chemistry of the
d-Block Elements
Another success story at the HEART of coordination chemistry:
Cardiolite
Chemistry of the
d-Block Elements
The d - Block Elements
http://www.chemsoc.org/viselements/pages/pertable_fla.htm
5
Chemistry of the
d-Block Elements
The d - Block Elements…my personal favorites
Chemistry of the
d-Block Elements
The d - Block Elements…my personal favorites
Prof. Karl Wieghardt
Max-Planck-Institute
for Bioinorganic Chemistry
Muelheim/Germany
6
Chemistry of the
d-Block Elements
The Werner & Jørgensen Controversy
Sophus Mads Jørgensen 1837 – 1914
Chemistry of the
d-Block Elements
Alfred Werner – Founder of Coordination Chemistry
“Dot” Representation:
Pentachlorophosphorous PCl5
PCl3 • Cl2
Copper(II) Sulfate Pentahydrate
CuSO4 • 5H2O
Copper(II) Acetate Hydrate
Cu(CH3COO)2 • H2O
Hex(a)ammin Cobalt(III) Chloride
CoCl3 • 6NH3
7
Chemistry of the
d-Block Elements
Alfred Werner
Seite 111 des 17-jährigen(!) Alfred Werner‘s
„Einleitung in die Chemie“ (1883 – 1884)
über die Formulierung des PCl5 als
molecular compound PCl3 • Cl2
Chemistry of the
d-Block Elements
Alfred Werner – Founder of Coordination Chemistry
Copper(II) Acetate Hydrate
Cu(CH3COO)2 • H2O
Hex(a)ammin Cobalt(III) Chloride
CoCl3 • 6NH3
8
Chemistry of the
d-Block Elements
Alfred Werner – Founder of Coordination Chemistry
Hex(a)ammin Cobalt(III) Chloride
CoCl3 • 6NH3
Prefix
Color
Complex
luteo
yellow
CoIIICl3 • 6NH3
purpureo
red
CoIIICl3 • 5NH3
praseo
green
CoIIICl3 • 4NH3
violeo
violet
CoIIICl3 • 4NH3
Chemistry of the
d-Block Elements
Alfred Werner – Founder of Coordination Chemistry
Alfred Werner‘s Kollektion (8000+ Komplexe!)
&
die „Katakomben“ an der Universität Zürich
9
Chemistry of the
d-Block Elements
Alfred Werner – Founder of Coordination Chemistry
Werner
Jørgensen
NH3—Cl
Co—NH3—Cl
NH3—NH3—NH3—NH3—Cl
[Co(NH3)6]Cl3
Cl
Co—NH3—Cl
NH3—NH3—NH3—NH3—Cl
[Co(NH3)5Cl]Cl2
[Co(NH3)4(Cl)2]Cl
!
rs
me
so
Cl
Co—Cl
NH3—NH3—NH3—Cl
[Co(NH3)4(Cl)2]Cl
2i
Cl
Co—Cl
NH3—NH3—NH3—NH3—Cl
Chemistry of the
d -Block Elements
Alfred Werner – Founder of Coordination Chemistry
10
Chemistry of the
d-Block Elements
Alfred Werner – Leitfähigkeit (Kohlrausch’s Prinzip, Konstitution)
Alfred Werner & Arturo Miolati (1893 – 1896)
Chemistry of the
d-Block Elements
Alfred Werner – Isomere (Konfiguration)
11
Chemistry of the
d-Block Elements
Alfred Werner – Founder of Coordination Chemistry
Chemistry of the
d-Block Elements
Alfred Werner – Founder of Coordination Chemistry
12
Chemistry of the
d-Block Elements
A Sidenote: Serendipity in Chemistry
Cisplatin was approved by the
FDA for the treatment of
genitourinary tumors in 1978.
Prof. Barnett Rosenberg, MSU
(Prof. S.J. Lippard, MIT)
Since then, Michigan State has
collected over $160 million in
royalties from cisplatin and a
related drug, carboplatin, which
was approved by the FDA in 1989
for the treatment of ovarian
cancers.
"Testicular cancer went from a disease that normally killed about
80% of the patients, to one which is close to 95% curable. This is
probably the most exciting development in the treatment of
cancers that we have had in the past 20 years. It is now the
treatment of first choice in ovarian, bladder, and osteogenic
sarcoma [bone] cancers as well."
O
NH 3
O
Pt
—Barnett Rosenberg, who led the research group that discovered
cisplatin, commenting on the impact of cisplatin in cancer
chemotherapy
O
NH 3
O carboplatin
Chemistry of the
d-Block Elements
First non-carbon containing chiral compound:
Hexol [(Co ((OH)2Co(NH3)4)3](SO4)3, resolved in 1914
with (+)-bromocamphorsulphonate
O
6+
O
Br
NH 3
S
O
O
NH 3
H 3N
H 3N
Co
NH 3
H 3N
H
O
O
H
NH 3
Co
HO
Co
NH 3
OH
OH
HO
H 3N
Co
NH 3
definitive proof of
Alfred Werner’s
octahedron model
-> Synthesis of
optically active
complexes!
NH 3
H 3N
13
Chemistry of the
d-Block Elements
Coordination Chemistry - Nomenclature
Chemistry of the
d-Block Elements
Coordination Chemistry - Nomenclature
14
Chemistry of the
d-Block Elements
Coordination Chemistry - Nomenclature
Chemistry of the
d-Block Elements
Coordination Chemistry - Nomenclature
15
Chemistry of the
d-Block Elements
Coordination Chemistry - Nomenclature
Chemistry of the
d-Block Elements
Coordination Chemistry - Nomenclature
16
Chemistry of the
d-Block Elements
Coordination Chemistry - Nomenclature
Chemistry of the
d-Block Elements
Coordination Chemistry - Nomenclature
17
Chemistry of the
d-Block Elements
Coordination Chemistry - Nomenclature
Chemistry of the
d-Block Elements
Coordination Chemistry - Nomenclature
18
Chemistry of the
d-Block Elements
Coordination Chemistry - Nomenclature
IUPAC Rules for complex formula:
• Coordination complex in square brackets,
charge superscripted
lo
I w oks
(B ou aw
r ) ( ld k w
Cl us ar
)(I e d…
)…
[CrIII(NCO)4(NH3)2] − [PtIIBrClI(NO2)(NH3)] −
[PtIVBrClI(NO2)(py)(NH3)]
• Central atom in front of ligands
abbrev: C5H5N
• Anionic in front of neutral ligands
• Multiple atoms & abbrev. ligands in round brackets
• Oxidation number superscripted @ central atom
Chemistry of the
d-Block Elements
Coordination Chemistry - Nomenclature
IUPAC Rules for complex name:
Main Difference: ligands first, followed by central atom
strictly follow alphabetical order
Dichloro(thiourea)(triphenylphosphine)platinum(II)
[PtCl2(py)(NH3)] Amminedichloro(pyridine)platinum(II)
• Ligands in alphabetical order in front of central atom/ion
Specification of oxidation number (Roman numerals) of the
central atom (or the charge number in Arabic numerals
after the name of the central atom)
Name of anionic ligands close with “o”, neutral ligands in
round brackets (except: ammine, aqua, carbonyl, nitrosyl)
19
Chemistry of the
d-Block Elements
Coordination Chemistry - Nomenclature
K3[Fe(CN)6]
Potassium-hexacyanoferrate(III) or
Potassium-hexacyanoferrate(3-)
(or Tripotassium-hexacyanoferrate)
K2[PtCl4]
Potassium-tetrachloroplatinate(II)
Na2[Fe(CO)4]
Disodium-tetracarbonylferrate
[Co(H2O)2(NH3)4]Cl3
Tetraammindiaquacobalt(3+)
chloride
Chemistry of the
d-Block Elements
Coordination Chemistry - Nomenclature
[Ni(H2O)(NH3)4]SO4
Na2[OsCl5N]
[CoCl(NO2)(NH3)4]Cl
[CoCl(NH2)(en)2]NO3
[FeH(CO)3(NO)]
[PtCl(NH2CH3)(NH3)]Cl
Tetra(a)mminediaquanickel(II)
sulfate
Disodium-pentachloronitridoosmate(VI)
Tetra(a)mminechloronitritocobalt(III) chloride
Amidochlorobis(ethylenediamine)
cobalt(III) nitrate
Tricarbonylhydridonitrosyliron(?)
Amminchlorobis(methylamine)
platinum(II) chloride
20
Chemistry of the
d-Block Elements
Coordination Chemistry - Nomenclature
Diamminediaquadicyanocobalt(III)
0
Cl
OC
Ru
PPh 3
PPh 3
H
PPh 3
+
OH 2
NC
Co
H N
H2 2
N
I I I NH 2
Co
NC
NH 2
N
NC
H2
H 2N
NH 3
OH 2
NC
NH 3
Carbonylchlorohydridotris(triphenylphosphine)
ruthenium(II)
CN
Ni
II
CN
CN
Tris(ethylenediamine)cobalt(III) pentacyanonickelate(II)
Chemistry of the
d-Block Elements
Coordination Chemistry - Isomers
Priority Rules: …remember Cahn-Ingold-Prelog?
practice…
3
NH3
1
HO
2
N
Pt
NH 3
3
6
CO
1
Br
Ph 3 P
3
2
Cl
N
M
5
NH 3
NM e3
4
N
N
H 3C
H
M
N
H 3 C CH 2
N
H
CH 3
N CH
3
N H
CH 3
H 3 C CHCH 3
3
21
Chemistry of the
d-Block Elements
Coordination Chemistry - Isomers
…in four-coordinate square-planar complexes:
cis-
&
trans-
and chiral isomers in
square planar complexes
chirality (chiral center) can be incorporated ligand
Chemistry of the
d-Block Elements
Coordination Chemistry - Isomers
…in six-coordinate octahedral complexes:
special case of cis- & transisomers:
carboxyl group
trans to tertiary N
carboxyl group
cis to tertiary N
22
Chemistry of the
d-Block Elements
Coordination Chemistry - Isomers
…in six-coordinate octahedral complexes:
in addition to cis- & transand chiral (Chapter 4)
isomers:
N
N
N
N
N
tacn
N
terpy
fac- and mer-isomers
more obvious with
poly (tri-)dentate
ligands such as:
tacn, tp- (fac)
or terpy (mer)
Chemistry of the
d-Block Elements
Coordination Chemistry - Isomers
…in six-coordinate octahedral complexes:
special case of
chirality in en
or tacn complexes:
N
N
NH2
N
NH 2
tacn, δδδ or λλλ
en
23
Chemistry of the
d-Block Elements
Coordination Chemistry - Isomers
Hydrate Isomerism
CrCl3 • 6H2O (dark green, mostly trans-[CrCl2(H2O)4]Cl)
[Cr(H2O)6]Cl3
blue-green
[CrCl(H2O)5]Cl2 • H2O
dark green
[CrCl2(H2O)4]Cl • 2H2O*
by
tion
ara n
sep ion io e
hy
cat hang grap
o
exc omat
ch r
violet
yellow-green [CrCl3(H2O)3] in conc. HCl
Chemistry of the
d-Block Elements
Coordination Chemistry - Isomers
Ionization Isomerism
[CoCl(NH3)4(H2O)]Br2 and [CoBr2(NH3)4]Cl • H2O
(also hydrate isomers)
[Co(SO4)(NH3)5]NO3
and [Co(NO3)(NH3)5]SO4
[CoCl(NO2)(NH3)4]Cl
and [CoCl2(NH3)4]NO2
24
Chemistry of the
d-Block Elements
Coordination Chemistry - Isomers
Coordination Isomerism
[Pt(NH3)4][PtCl4] (Magnus’ green salt)
different metal ions in different oxidation states:
[Co(en)3][Cr(CN)6] and
[Cr(en)3][Co(CN)6]
[Pt(NH3)4][PtCl6]
[PtCl2(NH3)4][PtCl4]
and
Chemistry of the
d-Block Elements
Coordination Chemistry - Isomers
Linkage (ambidentate) Isomerism
in
t
ra
m
ol
ec
ul
ar
!
Philip Coppens
University at
Buffalo (NY)
25
Chemistry of the
d-Block Elements
Coordination Chemistry - Isomers
Linkage (ambidentate) Isomerism
free rotation
large steric effect
isothiocyanato thiocyanato (1-diphenylphosphine-3dimethylaminepropane)palladium(II)
Chemistry of the
d-Block Elements
Coordination Chemistry – Coordination Numbers
& Structures
Notes & Blackboard
26
Chemistry of the
d-Block Elements
Coordination Chemistry – Bonding in TM Complexes
Ligand Fields & Ligand Strengths
High-Spin & Low-Spin Complexes
The Metals s-, p-, and d-Orbitals:
taken from:
Harvey & Porter
“Introduction to Physical Inorganic Chemistry”
Addison-Wesley 1963
Chemistry of the
d-Block Elements
The five d-orbitals
electron density
on the axes!
electron density in between the axes!
27
Chemistry of the
d-Block Elements
- Review Approx. dependency of orbital
energy on atomic number
(nuclear charge)
Schematic orbital energy diagram
taken from Harvey & Potter “Introduction to Physical
Inorganic Chemistry” Wesley 1963
Remember???
For example: Nickel (1s2)(2s22p6)(3s23p6) (4s2) (3d8)
In complexes: [Ni2+] (1s2)(2s22p6)(3s23p6)
(3d8) Æ unpaired electrons!!!
For a 3d electron: Z* = Z – S
Z*= 28 – [18 x (1.00)] – [7 x (o.35)] = 7.55
(1s, 2s, 2p, 3s, 3p)
(3d)
The 18 electrons in the 1s, 2s, 2p, 3s, and 3p levels contribute 1.00
each (Rule 3b); the other 7 electrons in 3d contribute 0.35 each,
and the 4s electrons do not contribute (Rule 2).
For a 4s electron: Z* = Z – S
Z* = 28 – [10 x (1.00)] – [16 x (o.85)] – [1 x (0.35)]
(1s, 2s, 2p)
(3s, 3p, 3d)
(4s)
Z* = 28 – 23.95 = 4.05 Æ The 4s electrons are held
less tightly than the 3d!
All transition metals loose ns electrons more readily
than (n – 1)d electron:
Ti(III): d1, V(III): d2, Mn(II): d5, Mn(III): d4, Mn(IV): d3, Mn(V): d2
28
Chemistry of the
d-Block Elements
Coordination Chemistry – Magnetism
A) Measurement of Susceptibility by Faraday’s Method
B) Measurement of Magnetization with a SQUID Magnetometer
Principle: In an inhomogeneous field a paramagnetic sample
is attracted into the zone with the largest field; a diamagnetic
sample is repulsed.
Chemistry of the
d-Block Elements
Coordination Chemistry – paired/unpaired d-electrons & magnetism
Measurement of Susceptibility by Faraday’s Method
dF = ½ μ0(χ – χmed)grad(H2)dv
Fz = μ0(χ – χmed)vH dH/dz
in vacuum or helium:
Fz = μ0χg m H(dH/dz) + F’
standard with known χg* and m*
χM = χg* [m* / (Fz* - F’)][Fz – F’)/m] M0
29
Chemistry of the
d-Block Elements
Coordination Chemistry – molecular magnetism
Chemistry of the
d-Block Elements
Coordination Chemistry – molecular magnetism
30
Chemistry of the
d-Block Elements
Coordination Chemistry – molecular magnetism
Chemistry of the
d-Block Elements
Coordination Chemistry – Bonding in TM Complexes
Ligand Fields & Ligand Strengths
High-Spin & Low-Spin Complexes
• Shape and Symmetry of Ligand and Metal Orbitals
• d-Orbital Splitting in Transition Metal Complexes:
1) Nature of the ligand
2) Symmetry of the Complex
31
Chemistry of the
d-Block Elements
Introduction - History
G. N. Lewis
Nevil Vincent Sidgwick
16. Febr. 1901 – 19. Aug. 1994
05. Mai. 1873 – 15. März 1952
Chemistry of the
d-Block Elements
Lewis Acid-Base Concept:
• Formation of Complexes via Ion-Ion and/or Ion-Dipole Forces:
Fe2+ + 4 Cl− Æ [FeCl4]−
ion ion
δ+
δ−
2+
Fe
+ 6 H2O Æ [Fe(OH2)6]2+
ion dipole
e-hole
e-pair
adduct
32
Chemistry of the
d-Block Elements
Lewis Acid-Base Concept:
• Formation of Complexes via Ion-Ion and/or Ion-Dipole Forces:
Fe2+ + 6 |CN− Æ [Fe(CN)6]4−
ion ion
Why not just 5 CN- ?
3d64s04p0 + 6 x 2 Æ 3d104s24p6 : 18 e- Krypton e-configuration
same with Fe(CO)5 but plenty of exceptions to the rule
K3[Fe(CN)6] (17e), [FeCl4]− (13e), ...
Chemistry of the
d-Block Elements
Valence-Bond Theory
Linus Pauling
16. Febr. 1901 – 19. Aug. 1994
only individual in history to have won
two unshared Nobel Prizes
in Chemistry (1954)
"for his research into the nature of the chemical bond and its application to the
elucidation of the structure of complex substances"
Nobel Peace Price (1962)
33
Chemistry of the
d-Block Elements
Valence-Bond Theory
Chemistry of the
d-Block Elements
Shortcomings of the Valence-Bond Theory
1) Fails to predict magnetic properties (unpaired electrons)
e.g.: i) all Co(III) Complexes are diamagnetic; except [CoF6]3-, [CoF3(H2O)3]
ii) Cr(III) in Oh: 3 unpaired e−; Cr(II) in Oh: predicted: 2e−, exp.: 4 unpaired e−
2) Ni(II) planar vs. octahedral is supposed to introduce change from covalent to ionic
e.g.: [Ni(en)2]2+ 2NH3 Æ [Ni(NH3)2(en)2]
3) Two Atomic Orbitals (AOs) produce MO(bonding) and MO(antibonding)
4) Color of Transition Metal Complexes! E.g.: [Ti(H2O)6]3+ λmax = 490 nm
34
Chemistry of the
d-Block Elements
Crystal Field Theory
Hans Bethe (PhD in theor. physics)
2. Juli 06 – 06. März 05 ;=)
Electrostatic Model:
M+ + L− Æ [M—L]
Underlying Principles:
♦ Ligand-Field Strength
♦ Asymmetric part of the electron interaction
♦ Spin-Orbit Splitting
Chemistry of the
d-Block Elements
σ - Symmetrical Metal-Ligand Interaction:
Note Symmetry of Orbitals!
s=g
p=u
d=g
f=u
taken from: Harvey & Porter “Introduction to Physical Inorganic Chemistry” Addison-Wesley 1963
35
Chemistry of the
d-Block Elements
Shortcomings of the Crystal-Field Theory
1) Ligands are not negatively charged hard spheres
2) Many complexes with significantly covalent bonds
Chemistry of the
d-Block Elements
Molecular Orbital Theory
Friedrich Hund
04. Febr. 1896 – 31. März 1997
36
Chemistry of the
d-Block Elements
Molecular Orbital Theory
Erich Hückel
1896 - 1980
Robert S. Mulliken
1896 - 1986
Chemistry of the
d-Block Elements
Molecular Orbital Theory
1) Considers IONIC as well as COVALENT bonding
2) Here: No Mathmatical but Phenomenological Considerations
3) MO Theory Contains Aspects of Valence-Bond (VB-) and Crystal-Field Theory
Molecular Orbitals (MOs) are formed via
Linar Combination of Atomic Orbitals (AOs)
metal center
orbital basis:
5x
nd - orbitals
1 x (n+1)s - orbital
3 x (n+1)p - orbitals
combines with
ligand
valence orbitals
Can be s, p, or spn
37
Chemistry of the
d-Block Elements
Molecular Orbital Theory
1) Only orbitals with same symmetry interact (e.g.: M=O or M≡O?)
2) For optimal interaction, energy difference should not be too large
(e.g.: H-H, H-Cl, NaCl)
3) The better the overlap, the better the orbital combination ( see 2. and distance)
Chemistry of the
d-Block Elements
Molecular Orbital Theory
six σ-orbitals arranged for an
octahedral complex (σ-Interactions only)
not covered in this lecture…
try at home!
taken from Riedel „Moderne Anorganische Chemie“ 2. Auflage
38
Chemistry of the
d-Block Elements
MO Theory
MO Diagram
for octhaedral (Oh)
σ−only complexes
CF
How is Δo (in σ-complexes)
explained in terms of
MO-Theory?
metal dorbitals
VB
ligand
orbitals
Chemistry of the
d-Block Elements
Molecular Orbital Theory
taken from Cotton, Wilkinson, Gaus „Grundlagen der Anorganischen Chemie“, VCH Verlag
39
Chemistry of the
d-Block Elements
Molecular Orbital Theory
taken from Cotton, Wilkinson, Gaus „Grundlagen der Anorganischen Chemie“, VCH Verlag
Chemistry of the
d-Block Elements
Molecular Orbital Theory
ΔE
Cl− vs F−
H3N vs H2O
H2O vs H2S ΔE
large ΔE between M and L orbitals
small ΔE between M and L orbitals
• weak orbital interaction
• small d-splitting (ligand field Δo)
• strong orbital interaction
• large d-splitting (ligand field Δo)
40
Chemistry of the
d-Block Elements
Molecular Orbital Theory
Introduction of metal-ligand
π−Interaction:
Chemistry of the
d-Block Elements
Molecular Orbital Theory
full σ-donor empty π-acceptor
orbital
orbital
full σ-donor full π-donor
orbital
orbital
Destabilization
Stabilization
41
Chemistry of the
d-Block Elements
Molecular Orbital Theory
Interpretation of the Spectrochemical Series in Terms of MO Theory
weak ligands
high-spin complexes
strong ligands
low-spin complexes
strong π-donor< weak π-donor < pure σ-donor < weak π-acceptor < strong π-acceptor
I− < Br− < S2− < SCN− < Cl− < NO3− < F−< OH− <
NO2− < CN− < PR3 < CO
H2O < NCS− < CH3CN < NH3 < en < bpy < phen <
Chemistry of the
d-Block Elements
Type
Description
Ligand examples
pπ—dπ
Donation of electrons from filled p-orbitals of
ligand to empty d-orbitals of metal
RO-, RS-, F-, Cl-,
R2N-
dπ—dπ
Donation of electrons from filled d-orbitals of
metal to empty d-orbitals of ligand
R2S (R3P, R3As)
dπ—π*
Donation of electrons from filled d-orbitals of
metal to empty π* (antibonding)-orbitals of
ligand
CO, RNC,
pyridine, CN-, N2,
NO2-, ethylene
dπ—σ*
Donation of electrons from filled d-orbitals of
metal to empty σ*-orbitals of ligand
H2, alkanes
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Chemistry of the
d-Block Elements
Molecular - Orbital Diagram
for Octahedral Complexes (σ - only)
Chemistry of the
d-Block Elements
43
Chemistry of the
d-Block Elements
Geometry (Symmetry) Dependence of Ligand—Field Splitting (cont’d):
44
A Case Study: The Electronic Structure of Hemoglobin/Myoglobin:
Geometry (Symmetry) Dependence of Ligand—Field Splitting (cont’d):
A Case Study: The Electronic Structure of Hemoglobin/Myoglobin:
Observation: Diamagnetic Spin Ground State for the Oxy-Form
of Hemoglobin/Myoglobin!
N
N
N
…with FeIII (S = 1/2 or 5/2) and 3O2 (S = 1)???
45
A Case Study: The Electronic Structure of Hemoglobin/Myoglobin:
Observation: Diamagnetic Spin Ground State for the Oxy-Form!
A Case Study: The Electronic Structure of Hemoglobin/Myoglobin:
Observation: Diamagnetic Spin Ground State for the Oxy-Form!
Solution A:
46
A Case Study: The Electronic Structure of Hemoglobin/Myoglobin:
Observation: Diamagnetic Spin Ground State for the Oxy-Form!
Solution B:
47