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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 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 …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