1. 23-1 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 23 The Transition Elements and Their Coordination Compounds

2. 23-2 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Transition Elements and Their Coordination Compounds 23.1 Properties of the Transition Elements 23.2 The Inner Transition Elements 23.3 Highlights of Selected Transition Metals 23.4 Coordination Compounds 23.5 Theoretical Basis for the Bonding and Properties of Complexes

3. 23-3 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 23.1 The transition elements (d block) and inner transition elements (f block) in the periodic table.

4. 23-4 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. General Properties: The transition metals show great similarities within a given period and a group. Their Chemistry does not change as number of valence electron change. They are metals good conductors of heat and electricity: Ex: Ag. More than one oxidation state.

5. 23-5 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. General Properties: Complex ions: Species where transition metal ion is surrounded by a certain number of ligands. Ligand: Molecules or ions that behave as Lewis bases. Paramagnetic-unpaired electrons.

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7. 23-7 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Electronic Configurations: Cr: Cu: Mo3+ Ag+ The energy of 3d orbitals in transition metal ions is less than 4s orbitals.

8. 23-8 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Atomic and Physical Properties of Transition Elements: 1. Atomic size decreases from left to right across the period, but then remain fairly constant. 2. Transition elements exhibit a small change in electronegativity. The values are intermediate. 3. First Ionization energies increase little. 4. Lanthanide contraction- 4f orbitals are filled, increases overall charge on nucleus and not the size.

9. 23-9 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 23.3 Horizontal trends in key atomic properties of the Period 4 elements.

10. 23-10 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Atomic and Physical Properties of Transition Elements: 5.Nuclear charge increases down a group. 6. Heavier transition metals exhibit more covalent character. 7. First I.E increases down a transitional group. 8. Densities increase as atomic mass increases.

11. 23-11 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 23.4 Vertical trends in key properties within the transition elements. 1 st IE highest at bottom of trans group. 2 nd and 3 rd element nearly same size Electronegativity increases down a group. Densities increase as mass increases

12. 23-12 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chemical Properties 1. They have multiple oxidation states. 2. +2 oxi state is most common as ns2 electrons are readily lost. 3. Ionic bonding occurs in lower O.S and covalent in higher O.S. 4. Electrons in a partially filled d sublevels can absorb visible wavelengths and hence their compounds are colored. 5. They are paramagnetic (unpaired d electrons) 6. IE1 increases down a group.

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14. 23-14 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sample Problem 23.2 SOLUTION: Finding the Number of Unpaired Electrons PROBLEM:The alloy SmCo 5 forms a permanent magent because both samarium and cobalt have unpaired electrons. How many unpaired electrons are in the Sm atom (Z = 62)? PLAN:Write the condensed configuration of Sm and, using Hund’s rule and the aufbau principle, place electrons into a partial orbital diagram. Sm is the eighth element after Xe. Two electrons go into the 6s sublevel and the remaining six electrons into the 4f (which fills before the 5d). Sm is [Xe]6s 2 4f 6 6s4f5d There are 6 unpaired e - in Sm.

15. 23-15 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Coordination compounds: They contain atleast one Complex ion, bonded to ligands and associated with other counter ions. Coordination compound: Complex transitional metal ion attached to ligands. Two types of valance: 1. secondary Valence- Ability of metal ion to bind to a Lewis base(ligands)- Coordination number. 2. Primary valence-Ability of metal ion to form ionic bonds with oppositely charged ions.-Oxidation state.

16. 23-16 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Coordination compounds: Complex ions: Species where transition metal ion is surrounded by a certain number of ligands. Ligand: Molecules or ions that behave as Lewis bases.

17. 23-17 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Structures of Complex Ions: Coordination Numbers, Geometries, and Ligands Coordination Number - the number of ligand atoms that are bonded directly to the central metal ion. The coordination number is specific for a given metal ion in a particular oxidation state and compound. Geometry - the geometry (shape) of a complex ion depends on the coordination number and nature of the metal ion. Donor atoms per ligand - molecules and/or anions with one or more donor atoms that each donate a lone pair of electrons to the metal ion to form a covalent bond.

18. 23-18 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The coordination number Varies from 2-8. 6 ligands-octahedral arrangement. 4-Tetrahedral/Square planar. 2- Linear. Most common coord. Number is 6.

19. 23-19 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 23.9 Components of a coordination compound. models wedge diagrams chemical formulas 6 ligands-octahedral 4 ligands-square planar

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21. 23-21 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Ligands: Neutral molecule or ion having a lone pair of electron that can be used to form a bond to metal ion. Metal (Lewis acid-e pair acceptor) _______ Nonmetal ( Lewis base- e pair donor) Monodentate/ Unidentate ligand- Ligand forms 1 bond.CN-, H2O, NH3.

22. 23-22 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Ligands Chelating ligands/ Chelates: Ligands have more than one atom with a lone pair of electrons that can be used to bond a metal ion. Bidentate ligand- can form 2 bonds.Ex: ethylenediamine(en), oxalate Polydentate ligands- can form more than 2 bonds.Ex: EDTA- 6 bonds.

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24. 23-24 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

25. 23-25 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Formulas and Names of Coordination Compounds Rules for writing formulas: 1. The cation is written before the anion. 2. The charge of the cation(s) is balanced by the charge of the anion(s). 3. In the complex ion, neutral ligands are written before anionic ligands, and the formula for the whole ion is placed in brackets.

26. 23-26 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Formulas and Names of Coordination Compounds continued Rules for naming complexes: 1. The cation is named before the anion. 2. Within the complex ion, the ligands are named, in alphabetical order, before the metal ion. 3. Neutral ligands generally have the molecule name, but there are a few exceptions. Anionic ligands drop the -ide and add -o after the root name. 4. A numerical prefix indicates the number of ligands of a particular type. 5. The oxidation state of the central metal ion is given by a Roman numeral (in parentheses). 6. If the complex ion is an anion we drop the ending of the metal name and add -ate.

27. 23-27 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nomenclature: Name cation before anion. In naming a complex ion, name ligands before the metal ion. In naming ligands, add o to the root name of anion(chloro), Use the full name for a neutral ligand. Exceptions to # 3: aqua, ammine, methylamine, carbonyl, nitrosyl.

28. 23-28 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nomenculature. Use prefix mono, di, tri, tetra, penta and hexa for simple ligands. 6. Use prefix bis,tris,tetrakis for complicated ligands that alreadt have bi,tri. 7. Oxidation state for metal in Roman numerals in () 8. When more than one type of ligand are present name alphabetically. 9. If complex ion has negative charge add the suffix - ate to the name of the metal.(Latin name) Iron copper lead silver gold tin

29. 23-29 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sample Problem 23.3 PROBLEM: PLAN: SOLUTION: Writing Names and Formulas of Coordination Compounds (a) What is the systematic name of Na 3 [AlF 6 ]? (b) What is the systematic name of [Co(en) 2 Cl 2 ]NO 3 ? (c) What is the formula of tetraaminebromochloroplatinum( IV ) chloride? (d) What is the formula of hexaaminecobalt (III ) tetrachloro- ferrate( III )? Use the rules presented - and. (a) The complex ion is [AlF 6 ] 3-. Six (hexa-) fluorines (fluoro-) are the ligands - hexafluoro Aluminum is the central metal atom - aluminate Aluminum has only the +3 ion so we don’t need Roman numerals. sodium hexafluoroaluminate

30. 23-30 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sample Problem 23.3Writing Names and Formulas of Coordination Compounds continued (b) There are two ligands, chlorine and ethylenediamine - dichloro, bis(ethylenediamine) The complex is the cation and we have to use Roman numerals for the cobalt oxidation state since it has more than one - (III ) The anion, nitrate, is named last. dichlorobis(ethylenediamine)cobalt(III) nitrate tetraaminebromochloroplatinum( IV ) chloride (c)4 NH 3 Br - Cl- Pt 4+ [Pt(NH 3 ) 4 BrCl]Cl 2 (d) hexaaminecobalt (III ) tetrachloro-ferrate( III ) 6 NH 3 Co 3+ 4 Cl - Fe 3+ [Co(NH 3 ) 6 ][Cl 4 Fe] 3

31. 23-31 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

32. 23-32 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ISOMERS Same chemical formula, but different properties Figure 23.10 Important types of isomerism in coordination compounds. Constitutional (structural) isomersStereoisomers Atoms connected differentlyDifferent spatial arrangement Coordination isomers Ligand and counter-ion exchange Coordination isomers Ligand and counter-ion exchange Linkage isomers Different donor atom Linkage isomers Different donor atom Geometric (cis- trans) isomers (diastereomers) Different arrangement around metal ion Geometric (cis- trans) isomers (diastereomers) Different arrangement around metal ion Optical isomers (enantiomers) Nonsuperimposable mirror images Optical isomers (enantiomers) Nonsuperimposable mirror images

33. 23-33 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Isomerism: Same formula but different properties. Structural isomerism: Isomers contain same atoms but different bonds. –Coordination isomerism: Composition of complex ion varies. Linkage isomerism: Point of attachment of atleast one of the ligands differs

34. 23-34 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Isomerism Stereoisomers: All bonds are same but different spatial arrangements. –Geometrical isomerism –cis-trans-Atoms or group of atoms can assume different positions around a rigid ring or bond. –Optical Isomerism: Have opposite effects on plane polarized light. Chiral: Objects that have nonsuperimposable mirror images. Enantiomers: Isomers that are nonsuperimposable mirror images of each other.

35. 23-35 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Linkage isomers

36. 23-36 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 23.11 Geometric (cis-trans) isomerism.

37. 23-37 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 23.12 Optical isomerism in an octahedral complex ion.

38. 23-38 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sample Problem 23.4 PLAN: SOLUTION: Determining the Type of Stereoisomerism PROBLEM:Draw all stereoisomers for each of the following and state the type of isomerism: (a) [Pt(NH 3 ) 2 Br 2 ](b) [Cr(en) 3 ] 3+ (en = H 2 NCH 2 CH 2 NH 2 ) Determine the geometry around each metal ion and the nature of the ligands. Place the ligands in as many different positions as possible. Look for cis-trans and optical isomers. (a) Pt( II ) forms a square planar complex and there are two pair of monodentate ligands - NH 3 and Br. cistrans These are geometric isomers; they are not optical isomers since they are superimposable on their mirror images.

39. 23-39 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sample Problem 23.4Determining the Type of Stereoisomerism continued(b) Ethylenediamine is a bidentate ligand. Cr 3+ is hexacoordinated and will form an octahedral geometry. Since all of the ligands are identical, there will be no geometric isomerism possible. The mirror images are nonsuperimposable and are therefore optical isomers.

40. 23-40 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 23.13 Hybrid orbitals and bonding in the octahedral [Cr(NH 3 ) 6 ] 3+ ion.

41. 23-41 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 23.14 Hybrid orbitals and bonding in the square planar [Ni(CN) 4 ] 2- ion.

42. 23-42 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 23.15 Hybrid orbitals and bonding in the tetrahedral [Zn(OH) 4 ] 2- ion.

43. 23-43 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Crystal Field Model It focuses on the energies of d orbitals. Metal –ligand bond is ionic. Ligands are negative point charges.

44. 23-44 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 23.16 An artist’s wheel.

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46. 23-46 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Octahedral complexes: Dz2 and dx2-y2 orbitals have lobes that point directly at the ligands. Dxy, dyz,dxy point their lobes between charges. Electrons fill the d orbitals farthest from the ligands to minimize repulsion. Dxy, dyz,dxy ( t2g set) are at lower energy in octahedral complex first. Dz2 and dx2-y2 (eg set) is at higher energy.

47. 23-47 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Octahedral complexes: Splitting of 3d orbital energies explains color and magnetism. Strong field case- splitting produced by ligands is very large, electrons will pair in lower t2g orbitals. Diamagnetic (all electrons are paired) Weak field case-splitting produced by ligands is small, electrons will occupy all 5 orbitals before pairing occurs. Paramagnetic( unpaired electrons)

48. 23-48 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 23.17 The five d-orbitals in an octahedral field of ligands.

49. 23-49 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Problems: 1.Fe (CN)63- has one unpaired electron. Does the CN- ligand produce a strong or weak field? 2.Predict the number of unpaired electrons in the complex ion [Cr(CN)6] 4 –

50. 23-50 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 23.22 The spectrochemical series. For a given ligand, the color depends on the oxidation state of the metal ion. For a given metal ion, the color depends on the ligand. I - < Cl - < F - < OH - < H 2 O < SCN - < NH 3 < en < NO 2 - < CN - < CO WEAKER FIELD STRONGER FIELD LARGER  SMALLER  LONGER SHORTER

51. 23-51 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Color of octahedral compounds: Absorbed color is different than observed color. Transition metals absorb colors in the visible region. ∆E=hc/, ∆E= energy spacing, =walength needed to move an electron from t2g to eg. Color of solution changes as the ligand changes.

52. 23-52 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. In tetrahedral complexes: None of the 3d orbitals point at the ligands. Tetrahedral splitting is 4/9 times that of octahedral. Dxy, dyz,dxy are closer to pint charges than Dz2 and dx2-y2. Weak field case always applies in tetrahedral complexes.

53. 23-53 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 23.18 Splitting of d-orbital energies by an octahedral field of ligands.  is the splitting energy

54. 23-54 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 23.19 The effect of ligand on splitting energy.

55. 23-55 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 23.20 The color of [Ti(H 2 O) 6 ] 3+.

56. 23-56 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 23.21 Effects of the metal oxidation state and of ligand identity on color. [V(H 2 O) 6 ] 2+ [V(H 2 O) 6 ] 3+ [Cr(NH 3 ) 6 ] 3+ [Cr(NH 3 ) 5 Cl ] 2+

57. 23-57 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Problem: Give the crystal field diagram for tetrahedral complex ion CoCl 4 2-

58. 23-58 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sample Problem 23.5 SOLUTION: Ranking Crystal Field Splitting Energies for Complex Ions of a Given Metal PROBLEM:Rank the ions [Ti(H 2 O) 6 ] 3+, [Ti(NH 3 ) 6 ] 3+, and [Ti(CN) 6 ] 3- in terms of the relative value of  and of the energy of visible light absorbed. PLAN:The oxidation state of Ti is 3+ in all of the complexes so we are looking at the crystal field strength of the ligands. The stronger the ligand the greater the splitting and the higher the energy of the light absorbed. The field strength according to is CN - > NH 3 > H 2 O. So the relative values of  and energy of light absorbed will be [Ti(CN) 6 ] 3- > [Ti(NH 3 ) 6 ] 3+ > [Ti(H 2 O) 6 ] 3+

59. 23-59 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 23.23 High-spin and low-spin complex ions of Mn 2+.

60. 23-60 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 23.24 Orbital occupancy for high- and low-spin complexes of d 4 through d 7 metal ions. high spin: weak-field ligand low spin: strong-field ligand high spin: weak-field ligand low spin: strong-field ligand

61. 23-61 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sample Problem 23.6 PLAN: SOLUTION: Identifying Complex Ions as High Spin or Low Spin PROBLEM:Iron ( II ) forms an essential complex in hemoglobin. For each of the two octahedral complex ions [Fe(H 2 O) 6 ] 2+ and [Fe(CN) 6 ] 4-, draw an orbital splitting diagram, predict the number of unpaired electrons, and identify the ion as low or high spin. The electron configuration of Fe 2+ gives us information that the iron has 6d electrons. The two ligands have field strengths shown in. Draw the orbital box diagrams, splitting the d orbitals into e g and t 2g. Add the electrons noting that a weak-field ligand gives the maximum number of unpaired electrons and a high-spin complex and vice-versa. t 2g egeg egeg potential energy [Fe(H 2 O) 6 ] 2+ [Fe(CN) 6 ] 4- no unpaired e -- (low spin) 4 unpaired e -- (high spin)

62. 23-62 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 23.25 Splitting of d-orbital energies by a tetrahedral field and a square planar field of ligands. tetrahedral square planar

63. 23-63 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure B23.1 Hemoglobin and the octahedral complex in heme.

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65. 23-65 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure B23.2 The tetrahedral Zn 2+ complex in carbonic anhydrase.