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Transition Elements and Coordination Chemistry

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Presentation on theme: "Transition Elements and Coordination Chemistry"— Presentation transcript:

1 Transition Elements and Coordination Chemistry

2 Chem 1A Review Why Study Coordinated Complexes of Transition metals?
These compounds are used as catalyst in oxidation of organic compounds and pharmaceutical applications. Chem 1A Review Chapter 20

3 Order of orbitals (filling) in multi-electron atom
1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f< 5d< 6p< 7s< 5f< 6d< 7p Chapter 20

4 Chapter 20

5 Electron Configuration and the Periodic Table
ns2np6 Electron Configuration and the Periodic Table ns1 ns2np1 ns2np2 ns2np3 ns2np4 ns2np5 ns2 d10 d1 d5 4f 5f Chapter 20

6 Using periodic table write Noble gas notation
for the following elements: [Ne]3s23p4 a)S [Ar] 4s23d6 b)Fe [Ar] 4s23d104p4 c)Se [Xe]6s24f75d1 d)Gd 1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f< 5d< 6p< 7s< 5f< 6d< 7p

7 Chapter 20

8 Electron Configurations
Chapter 20

9 Why Study Coordinated Complexes of Transition metals?
Are used as catalyst in oxidation of organic compounds. Medicinal applications. “Cisplatin” - a cancer chemotherapy agent Chapter 20

10 Coordination Compounds
Pt(NH3)2Cl2 “Cisplatin” - a cancer chemotherapy agent Co(H2O)62+ Cu(NH3)42+ Chapter 20

11 Coordination Compounds of Ni2+
[Ni(NH3)6]+2 [Ni(NH2C2H4NH2)3]+2 Chapter 20

12 Electron Configurations
Sc (Z = 21): [Ar] 3d1 4s2 Zn (Z = 30): [Ar] 3d10 4s2 Remember that it’s common to list the s electrons last since they are removed first when forming ions. Chapter 20

13 Coordination Compounds
Omit Coordination Compounds Many coordination compound consists of a complex ion. A complex ion contains a central metal cation bonded to one or more molecules or ions. The molecules or ions that surround the metal in a complex ion are called ligands. A ligand has at least one unshared pair of valence electrons H N H O Cl - C O Chapter 20

14 Coordination Compounds
The atom in a ligand that is bound directly to the metal atom is the donor atom. H N H O Ligands with: one donor atom monodentate H2O, NH3, Cl- two donor atoms bidentate ethylenediamine three or more donor atoms polydentate EDTA The number of donor atoms surrounding the central metal atom in a complex ion is the coordination number. Chapter 20

15 Coordination Compounds
Coordination Number: The number of ligand donor atoms that surround a central metal ion or atom. Chapter 20

16 Ligands 02 Chapter 20

17 Ligands 03 Chapter 20

18 Poly DentateLigands EDTA4– is often used to treat heavy metal poisoning such as Hg2+, Pb2+, and Cd2+. EDTA4– bonds to Pb2+, which is excreted by the kidneys as [Pb(EDTA)]2–. Chapter 20

19 Coordination Compounds
H2N CH2 CH NH2 bidentate ligand polydentate ligand (EDTA) Bidentate and polydentate ligands are called chelating agents Chapter 20

20 What is the Oxidation Numbers of Cu?
Naming coordinated complex compounds What is the Oxidation Numbers of Cu? +2 Knowing the charge on a complex ion and the charge on each ligand, one can determine the oxidation number for the metal. Chapter 20

21 Oxidation Number Rules
Applies to Statement 1 Elements The oxidation number of an atom in an element is zero. 2 Monatomic ions The oxidation number of an atom in a monatomic ion equals the charge of the ion. 3 Oxygen The oxidation number of oxygen is –2 in most of its compounds. (An exception is O in H2O2 and other peroxides, where the oxidation number is –1.) Chapter 20

22 Oxidation Number Rules
Applies to Statement 4 Hydrogen +1, it will be -1 when hydrogen comes with metal. NaH 5 Halogens Fluorine is –1 in all its compounds. Each of the other halogens is –1 in binary compounds unless the other element is oxygen. 6 Compounds and ions The sum of the oxidation numbers of the atoms in a compound is zero. The sum in a polyatomic ion equals the charge on the ion. Chapter 20

23 What is the charge on the following Complex, If the Oxidation number of Cr is +3?
Or, knowing the oxidation number on the metal and the charges on the ligands, one can calculate the charge on the complex ion. Chapter 20

24 What are the oxidation numbers of the metals in K[Au(OH)4] and [Cr(NH3)6](NO3)3 ?
OH- has charge of -1 K+ has charge of +1 ? Au x(-1) = 0 NO3- has charge of -1 Au = +3 NH3 has no charge ? Cr + 6x(0) + 3x(-1) = 0 Cr = +3 Chapter 20

25 Oxidation States of the 1st Row Transition Metals
(most stable oxidation numbers are shown in red) Chapter 20

26 Learning Check A complex ion contains a Cr3+ bound to four H2O molecules and two Cl– ions. Write its formula. +1 Chapter 20

27 N [Ag(NH3)2]2 SO4 Coordination Sphere Coordinate bond: N
Coordination Sphere: is the central metal and surrounding ligands. The square brackets separate the complex from counter ions such as SO42–. N N N [Ag(NH3)2]2 SO4 Chapter 20

28 Geometry of Coordination Compounds
Coordination number Structure 2 Linear 4 Tetrahedral or Square planar (mostly d8 ) 6 Octahedral Chapter 20

29 Coordination Number of 7&8
Geometry Pentagonal bipyramid Hexagonal bipyramid Coordination Number of 7 Coordination Number of 8 Chapter 20

30 Coordination Compounds
Geometries: Chapter 20

31 Nomenclature Co(H2O)62+ Hexaaquacobalt(II) H2O as a ligand is aqua
Cu(NH3)42+ Tetraamminecopper(II) Pt(NH3)2Cl2 diamminedichloroplatinum(II) NH3 as a ligand is ammine Systematic naming specifies the type and number of ligands, the metal, and its oxidation state. Chapter 20

32 Ligand’s Names 01 Chapter 20

33 Chapter 20

34 Nomenclature Chapter 20

35 Nomenclature Systematic naming follows IUPAC rules:
If compound is a salt, name cation first and then the anion, just as in naming simple salts. In naming a complex ion or neutral complex, name ligands first and then the metal. If the complex contains more than one ligand of a particular type, indicate the number with the appropriate Greek prefix: di–, tri–, tetra–, penta–, hexa–. Chapter 20

36 Nomenclature If the name of a ligand itself contains a Greek prefix, (ethylenediamine or triphenylphosphine) put the ligand name in parentheses and use: bis (2), tris (3), or tetrakis (4). Use a Roman numeral in parentheses, immediately following the name of the metal, to indicate the metal’s oxidation state. In naming the metal, use the ending –ate if metal is in an anionic complex. Chapter 20

37 Name the following Complexes:
Tris(ethylenediamine)nickel(II) Pt( [Ni(NH2C2H4NH2)3]2+ IrCl(CO)(PPh3)2 Carbonylchlorobis(triphenylphosphine)iridium(I) Chapter 20

38 What is the systematic name of [Cr(H2O)4Cl2]Cl ?
tetraaquadichlorochromium(III) chloride Write the formula of tris(ethylenediamine)cobalt(II) sulfate [Co(en)3]SO4 Chapter 20

39 Constitutional Isomerism
1. Constitutional Isomers: Have different bonds among their constituent atoms. Ionization Isomers : [Co(NH3)5Br]SO4 (violet compound with Co–Br bond), [Co(NH3)5 SO4]Br (red compound with Co–SO4 bond). Linkage Isomers form when a ligand can bond through two different donor atoms. Consider [Co(NH3)5NO2]2+ which is yellow with the Co–NO2 bond and red with the Co–ONO bond. Chapter 20

40 Such a transformation could be used as an energy storage device.
Linkage Isomerism sunlight Such a transformation could be used as an energy storage device. Chapter 20

41 2.Stereoisomers Geometric Isomers of Pt(NH3)2Cl2: In the cis isomer, atoms are on the same side. In the trans isomer, atoms are on opposite sides. DNA-damaging antitumor agents Inactive

42 2.Stereoisomers Geometric Isomers have the same connections among atoms but different spatial orientations of the metal–ligand bonds. cis isomers have identical ligands in adjacent corners of a square. trans isomers have identical ligands across the corners from each other. Chapter 20

43 Isomers Geometric Isomers of [Co(NH3)4Cl2]Cl: Chapter 20

44 Enantiomers Chapter 20

45 Enantiomers Enantiomers are stereoisomers of molecules or ions
that are nonidentical mirror images of each other. Objects that have “handedness” are said to be chiral, and objects that lack “handedness” are said to be achiral. An object or compound is achiral if it has a symmetry plane cutting through the middle. Chapter 20

46 Enantiomers Chapter 20

47 © 2003 John Wiley and Sons Publishers
Unpolarized light. Chapter 20

48 Plane-polarized light.
© 2003 John Wiley and Sons Publishers Plane-polarized light. Chapter 20

49 Reflected glare is plane-polarized light.
© 2003 John Wiley and Sons Publishers Reflected glare is plane-polarized light. Chapter 20

50 Polarizing sunglasses versus glare.
© 2003 John Wiley and Sons Publishers Polarizing sunglasses versus glare. Chapter 20

51 The effect of polarizing lenses on unpolarized light.
© 2003 John Wiley and Sons Publishers Courtesy Andy Washnik The effect of polarizing lenses on unpolarized light. Chapter 20

52 plane-polarized light
Chapter 20

53 Enantiomers and Molecular Handedness
Chapter 20

54 Enantiomers Enantiomers have identical properties except for their
reaction with other chiral substances and their effect on plane-polarized light. Enantiomers are often called optical isomers; their effect on plane-polarized light can be measured with a polarimeter. Chapter 20

55 Enantiomers Plane-polarized light is obtained by passing ordinary light through a polarizing filter. In a polarimeter the plane-polarized light is passed through a chiral solution and the polarization plane measured with an analyzing filter. If the plane rotates to the right it is dextrorotatory. If the plane rotates to the left it is levorotatory. Equal amounts of each are racemic. Chapter 20

56 Isomers 01 Chapter 20

57 sunlight See next slide for Diastereoisomers [Co(NH3)5Br]SO4 (violet),
[Co(NH3)5 SO4]Br (red ). sunlight See next slide for Diastereoisomers

58 Diasteromers Chapter 20

59 Bonding in Complexes 01 Bonding Theories attempt to account for the color and magnetic properties of transition metal complexes. Ni Cu2+ Co2+ Zn2+ Solutions of [Ni(H2O)6]2+, [Ni(NH3)6]2+, & [Ni(en)3]2+ Chapter 20

60 Color of Transition Metal Complexes
DE = E2 - E1 = hn = l hc or Using c = ln. DE hc l = Chapter 20

61 Color of Transition Metal Complexes
Chapter 20

62 Color of Transition Metal Complexes
Chapter 20

63 Bonding in Complexes: Valence Bond Theory
Chapter 20

64 Bonding in Complexes: Which empty orbital is metal using for bonding S, p, d or f ?
The complex is paramagnetic since there are 1 or more unpaired electrons. Chapter 20

65 Hybridization and sp3 Hybrid Orbitals
How can the bonding in CH4 be explained? 4 valence electrons 2 unpaired electrons How can carbon have 4 bonds if there are only 2 unpaired valence electrons? Chapter 20

66 Hybridization and sp3 Hybrid Orbitals
How can the bonding in CH4 be explained? 4 valence electrons 4 unpaired electrons Promotion of 1 electron allows for 4 unpaired valence electrons. Chapter 20

67 Hybridization and sp3 Hybrid Orbitals
How can the bonding in CH4 be explained? 4 nonequivalent orbitals The 4 bonds in CH4 must be equivalent (tetrahedral distribution). Chapter 20

68 Hybridization and sp3 Hybrid Orbitals
How can the bonding in CH4 be explained? 4 equivalent orbitals Chapter 20

69 Hybridization and sp3 Hybrid Orbitals
Chapter 20

70 Hybridization and sp3 Hybrid Orbitals
Chapter 20

71 Other Kinds of Hybrid Orbitals
Summary. Chapter 20

72 Hybrid Orbitals in Coordinated Complexes
We should look at magnetic property of the complex to see if they are high or low spin. Then we could decide whether they are using d2sp3 or sp3d2 hybrid

73 The octahedral d2sp3 and sp3d2
Chapter 20

74 Square Planar geometry of four dsp2
Chapter 20

75 Bonding in Complexes: Valence Bond Theory
The complex is paramagnetic since there are 1 or more unpaired electrons. Experimental results: High Spin Chapter 20

76 Bonding in Complexes: Valence Bond Theory
The complex is diamagnetic since there are 1 or more unpaired electrons. Experimental results: Low Spin Chapter 20

77 High- and Low-Spin Complexes
Experimental results : High Spin [CoF6]3- [Co(CN)6]3- High spin: Maxium number of unpaired electron, Paramagnetic Low spin: Minimum number of unpaired electron Chapter 20

78 Crystal Field Theory Crystal Field Theory:
Effect of charges of ligand on transition metal d-electrons. A model that views the bonding in complexes as arising from electrostatic interactions and considers the effect of the ligand charges on the energies of the metal ion d orbitals. Only electrostatic interactions- no covalent bonds, no shared electrons, and no hybrid orbitals. Chapter 20

79 Directed between ligands
Crystal Field Theory Octahedral Complexes Directed between ligands Directed at ligands Chapter 20

80 Crystal Field Theory Octahedral Complexes Chapter 20

81 [Ni(X)6]2+ X=H2O, NH3, and ethylenediamine (en)
Crystal Field Theory Octahedral Complexes [Ni(X)6]2+ X=H2O, NH3, and ethylenediamine (en) [Ti(H2O)6]3+ see p845 fig 20.25 [Ni(H2O6]2+ see p844 fig 20.24 (red-violet) Chapter 20

82 [Ti(H2O)6]3+ Chapter 20

83 Crystal Field Theory Octahedral Complexes
The crystal field splitting changes depending on nature of the legand. [Ni(X)6]2+ X=H2O, NH3, and ethylenediamine (en) Chapter 20

84 The absorption maximum for the complex ion [Co(NH3)6]3+ occurs at 470 nm. What is the color of the complex and what is the crystal field splitting in kJ/mol? hc l = DE = hn = 4.23 x J DE (kJ/mol) ? = 255 kJ/mol Chapter 20


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