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:
H3N NH3 Cl Cl Pd Pd NH H3N 3 Cl Cl
Louis Nicolas Vauquelin 1813 CN
NC CN CoIII NC CN Gmelin 1822 NC
1 Chemistry of the d-Block Elements
History:
1844: Peyrone’s Chloride 1844: Reiset
[PtCl2(NH3)2] -- note! same formula! -- [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. Since then, Michigan State has collected over $160 million in royalties from cisplatin and a related drug, carboplatin, which Prof. Barnett Rosenberg, MSU was approved by the FDA in 1989 (Prof. S.J. Lippard, MIT) 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 Newest generation: probably the most exciting development in the treatment of cancers that we have had in the past 20 years. It is now the O treatment of first choice in ovarian, bladder, and osteogenic sarcoma [bone] cancers as well." O NH3 —Barnett Rosenberg, who led the research group that discovered Pt cisplatin, commenting on the impact of cisplatin in cancer chemotherapy O NH3 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
SUMMARY: The anticancer activity of cis -diamminedichloroplatinum(II) (cisplatin) arises from its ability to damage DNA, with the major adducts formed being intrastrand Barnett Rosenberg, MSU (1926 - ) 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
SUMMARY: The anticancer activity of cis -diamminedichloroplatinum(II) (cisplatin) arises from its ability to damage DNA, with the major adducts formed being intrastrand Stephen J. Lippard, MIT (??? - ) 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
III • luteo yellow Co Cl3 6NH3
III • purpureo red Co Cl3 5NH3
III • praseo green Co Cl3 4NH3
III • violeo violet Co Cl3 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
Jørgensen Werner NH3—Cl Co—NH3—Cl [Co(NH3)6]Cl3 NH3—NH3—NH3—NH3—Cl
Cl
Co—NH3—Cl [Co(NH3)5Cl]Cl2 NH3—NH3—NH3—NH3—Cl
Cl Co—Cl 2 [Co(NH3)4(Cl)2]Cl i NH3—NH3—NH3—NH3—Cl s o m e r Cl s Co—Cl ! [Co(NH3)4(Cl)2]Cl 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. Since then, Michigan State has collected over $160 million in royalties from cisplatin and a related drug, carboplatin, which Prof. Barnett Rosenberg, MSU was approved by the FDA in 1989 (Prof. S.J. Lippard, MIT) 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 O treatment of first choice in ovarian, bladder, and osteogenic sarcoma [bone] cancers as well." O NH3 —Barnett Rosenberg, who led the research group that discovered Pt cisplatin, commenting on the impact of cisplatin in cancer chemotherapy O NH3 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 O 6+ Br S NH3 O O H 3N NH3 Co definitive proof of NH3 HO H NH3 Alfred Werner’s H 3N O OH octahedron model Co Co H 3N O -> Synthesis of H OH NH HO optically active 3 NH Co 3 complexes! H 3N NH3
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 l oo IUPAC Rules for complex formula: I ks w aw (B ou r) ld k (C u w l s ar • Coordination complex in square brackets, )( e d… I)… charge superscripted
III − II − [Cr (NCO)4(NH3)2] [Pt BrClI(NO2)(NH3)]
IV [Pt BrClI(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 Tetra(a)mminediaquanickel(II) sulfate
Na2[OsCl5N] Disodium-pentachloronitrido- osmate(VI)
[CoCl(NO2)(NH3)4]Cl Tetra(a)mminechloronitrito- cobalt(III) chloride
[CoCl(NH2)(en)2]NO3 Amidochlorobis(ethylenediamine) cobalt(III) nitrate
[FeH(CO)3(NO)] Tricarbonylhydridonitrosyliron(?)
[PtCl(NH2CH3)(NH3)]Cl Amminchlorobis(methylamine) platinum(II) chloride
20 Chemistry of the d-Block Elements
Coordination Chemistry - Nomenclature
Diamminediaqua- dicyanocobalt(III)
Cl 0+ OH2 H 2N CN H 2 PPh NC NH N III NH OC 3 3 2 II Ru Ni Co Co NC CN PPh H 3 NC OH2 N NH2 NC CN H 2 PPh 3 NH3 H 2N
Carbonylchloro- Tris(ethylenediamine)- hydridotris(tri- cobalt(III) pentacyano- phenylphosphine) nickelate(II) ruthenium(II)
Chemistry of the d-Block Elements
Coordination Chemistry - Isomers Priority Rules: …remember Cahn-Ingold-Prelog? practice…
6 CO N 1 3 2 H HO NH 1 CH 3 Br Cl N N N 3 Pt M CH 3 2 H M NH Ph P NH3 N H N 3 3 5 H 3C N 3 CH 3 H C CH 3 NMe3 3 2 N 4 CH H 3C 3 CH 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- & trans- isomers:
carboxyl group carboxyl group trans to tertiary N cis to tertiary N
22 Chemistry of the d-Block Elements
Coordination Chemistry - Isomers
…in six-coordinate octahedral complexes: in addition to cis- & trans- and chiral (Chapter 4) isomers:
fac- and mer-isomers N more obvious with NN N poly (tri-)dentate N N ligands such as: tacn, tp- (fac) tacn terpy 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
NN NH2
NH2 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) s c e e a p t a violet [Cr(H O) ]Cl c x i 2 6 3 c o r h a r h n o a t i io m n o n g n a blue-green [CrCl(H2O)5]Cl2 •H2O t e b o y g r a p dark green [CrCl2(H2O)4]Cl • 2H2O* h y
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] and [PtCl2(NH3)4][PtCl4]
Chemistry of the d-Block Elements
Coordination Chemistry - Isomers
Linkage (ambidentate) Isomerism
in tr am o lec u la r!
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-3- dimethylaminepropane)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 Schematic orbital energy diagram (nuclear charge)
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
2 dF = ½ μ0(χ – χmed)grad(H )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:
2+ − − Fe + 4 Cl Æ [FeCl4] ion - ion
δ+ δ− 2+ 2+ Fe + 6 H2O Æ [Fe(OH2)6] 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:
2+ − 4− Fe + 6 |CN Æ [Fe(CN)6] 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) 3- e.g.: i) all Co(III) Complexes are diamagnetic; except [CoF6] , [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 2+ e.g.: [Ni(en)2] 2NH3 Æ [Ni(NH3)2(en)2]
3) Two Atomic Orbitals (AOs) produce MO(bonding) and MO(antibonding)
3+ 4) Color of Transition Metal Complexes! E.g.: [Ti(H2O)6] 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 Robert S. Mulliken 1896 - 1980 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: combines with 5 x nd - orbitals ligand 1 x (n+1)s - orbital valence orbitals 3 x (n+1)p - 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 not covered in this lecture… octahedral complex (σ-Interactions only) 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 Δ (in σ-complexes) o metal d- VB explained in terms of orbitals ligand MO-Theory? 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
Cl− vs F−
H3N vs H2O ΔE ΔE H2O vs H2S
large ΔE between M and L orbitals small ΔE between M and L orbitals
• weak orbital interaction • strong orbital interaction
• small d-splitting (ligand field Δo) • 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 full σ-donor full π-donor orbital orbital 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 strong ligands high-spin complexes low-spin complexes
strong π-donor< weak π-donor < pure σ-donor < weak π-acceptor < strong π-acceptor
− − 2− − − − − − − − I < Br < S < 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
Donation of electrons from filled p-orbitals of RO-, RS-, F-, Cl-, pπ—dπ - ligand to empty d-orbitals of metal R2N Donation of electrons from filled d-orbitals of R S (R P, R As) dπ—dπ 2 3 3 metal to empty d-orbitals of ligand Donation of electrons from filled d-orbitals of CO, RNC, - dπ—π* metal to empty π* (antibonding)-orbitals of pyridine, CN , N2, - ligand NO2 , ethylene Donation of electrons from filled d-orbitals of H , alkanes dπ—σ* 2 metal to empty σ*-orbitals of ligand
42 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
III 3 …with Fe (S = 1/2 or 5/2) and O2 (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