Coordination Complexes Chapter 20

Copyright © Houghton Mifflin Company. All rights reserved.20 | 2 What we learn from Chap 20 We begin the chapter with what is among the most important coordination complexes of all, iron in hemoglobin (magnesium in chlorophyll might be another). In Section 20.1, we introduce the coordinate covalent bond and reintroduce Lewis acids (central atom) and bases (ligands) as the bonding species in coordination complexes. We also discuss how carbon monoxide can replace oxygen in hemoglobin.

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Copyright © Houghton Mifflin Company. All rights reserved.20 | 4 CHAPTER OUTLINE I.Bonding in Coordination Complexes II.Ligands III.Coordination Number IV.Structure V.Isomers VI.Formulas and Names A. Formulas B. Nomenclature VII.Color and Coordination Compounds A. Transition Metals and Color B. Crystal-Field Theory C. Orbital Occupancy D. The Result of d Orbital Splitting E. Magnetism VIII.Chemical Reactions A. Ligand Exchange Reactions B. Electron Transfer Reactions

Copyright © Houghton Mifflin Company. All rights reserved.20 | Coordination Complex Central metal atom – transition metal. Coordinate covalent bond Ligand – anion or neutral compound such as H 2 O: or :NH 3. [Cu(NH 3 )] 2+ [Fe(CN) 6 ] 3- ·

Copyright © Houghton Mifflin Company. All rights reserved.20 | 6 Complexes Protein FerrodoxinPlastocyanin Wilkin’s catalysyst

Copyright © Houghton Mifflin Company. All rights reserved.20 | Ligands Lewis bases having a lone pair of e - to donate. Bidentate ligands form two bonds to the metal. Chelates are polydentate ligands.

Copyright © Houghton Mifflin Company. All rights reserved.20 | 8 Ligand Names

Copyright © Houghton Mifflin Company. All rights reserved.20 | 9 Ligands

Copyright © Houghton Mifflin Company. All rights reserved.20 | 10 Chelate

Copyright © Houghton Mifflin Company. All rights reserved.20 | 11 EDTA

Copyright © Houghton Mifflin Company. All rights reserved.20 | 12 EDTA

Copyright © Houghton Mifflin Company. All rights reserved.20 | Coordination Number Coordination number (CN) is the number of donor atoms bonded to central metal atom. Common coordination numbers are 4 and 6. May be as low as 2 and as high as 8. CN determined by –The nature of metal ions : eg. Size –Charge on the ligand & metal –Electron configuration of metal

Copyright © Houghton Mifflin Company. All rights reserved.20 | 14 Coordination Number

Copyright © Houghton Mifflin Company. All rights reserved.20 | 15 Coordination Number

Copyright © Houghton Mifflin Company. All rights reserved.20 | Structure CN = 2 –linear complex, 180 o bond angles. CN = 4 –tetrahedral complex, 109 o bond angles. –square planar complex (nd 8 electron configuration), 90 o bond angles. CN = 6 –octahedral complex, 90 o bond angles.

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Copyright © Houghton Mifflin Company. All rights reserved.20 | 18 CN = 4 Tetrahedral eg) Zn(NH 3 ) 4 2+, CoCl 4 2- cf) VSEPR Model Square planar eg) Cu(NH 3 ) 4 2+, Ni(II), Pd(II), Pt(II)

Copyright © Houghton Mifflin Company. All rights reserved.20 | 19 Sample Problem Predict the geometry of the following complexes: [Ni(NH 3 ) 6 ]2 + [Pt(NH 3 ) 2 Cl 2 ] [Au(CN)] + [Ni(NH 3 ) 6 ]2 + [Pt(NH 3 ) 2 Cl 2 ] [Au(CN)] + CN = 6, octahedral CN = 4, square planar CN = 2, linear

Copyright © Houghton Mifflin Company. All rights reserved.20 | Isomers

Copyright © Houghton Mifflin Company. All rights reserved.20 | 21 Linkage Isomer

Copyright © Houghton Mifflin Company. All rights reserved.20 | 22 Ionization Isomers

Copyright © Houghton Mifflin Company. All rights reserved.20 | 23 Coordination (sphere) isomers

Copyright © Houghton Mifflin Company. All rights reserved.20 | 24 Geometric Isomers - SP Cisplatin

Copyright © Houghton Mifflin Company. All rights reserved.20 | 25 Geometric Isomers - Oh

Copyright © Houghton Mifflin Company. All rights reserved.20 | 26 Geometric Isomerism

Copyright © Houghton Mifflin Company. All rights reserved.20 | 27 Optical Isomerism

Copyright © Houghton Mifflin Company. All rights reserved.20 | Formulas

Copyright © Houghton Mifflin Company. All rights reserved.20 | 29 Naming Coordination Compounds

Copyright © Houghton Mifflin Company. All rights reserved.20 | 30 Sample Problem Write the formulas for the following: Sodium hexafluorocobaltate(III) Bisethylenediaminecopper(II) chloride Sodium hexafluorocobaltate(III) = Na 3 [CoF 6 ] Bisethylenediaminecopper(II) chloride=[Cu(en) 2 ]Cl 2

Copyright © Houghton Mifflin Company. All rights reserved.20 | 31 Sample Problem Name the following coordination compounds: [Co(H 2 O) 2 Cl 2 ]ClK 3 [Fe(CN) 6 ] [Co(H 2 O) 2 Cl 2 ]Cldiaquodichlorocobalt(III) chloride K 3 [Fe(CN) 6 ]potassium hexacyanoferrate(III)

Copyright © Houghton Mifflin Company. All rights reserved.20 | 32 K 2 [NiCl 4 ] [Co(NH 3 ) 6 ]Cl 3 [Co(NO 2 ) 2 (NH 3 ) 4 ] 2 SO 4 Diamminebis(ethylenediamine) chronium(II) sulfate Ammonium hexacyanoferrate(III) Potassium tetrachloronikelate(II) Hexaamminecobalt(III) Chloride Diamminedinitrocobalt(IV) sulfate [Cr(NH 3 ) 2 (en) 2 ]SO 4 (NH4) 3 [Fe(CN) 3 ]

Copyright © Houghton Mifflin Company. All rights reserved.20 | Color and Coordination Compounds Coordination compounds are usually colored. The color is due to partially filled d orbitals separated by an energy difference. A photon causes a lower energy electron to move to a higher energy level. The color is the results of the light, missing the absorbed photon, being reflected from the metal.

Copyright © Houghton Mifflin Company. All rights reserved.20 | 34 Color and Coordination Compounds

Copyright © Houghton Mifflin Company. All rights reserved.20 | 35 Crystal Field Theory A free gaseous metal atom or ion does not show an energy level difference among the d orbitals. In the presence of ligands, the d orbital of the metal are split by a slight energy difference, Δ o

Copyright © Houghton Mifflin Company. All rights reserved.20 | 36 Crystal Field Splitting

Copyright © Houghton Mifflin Company. All rights reserved.20 | 37 결정장모델 (Crystal Field Model) Free metal ion in Spherical field in Oh field small  o large  o E oo oo Approach of six ligands to transition metal cation splits d orbitals into two sets of different energy: explain color and magnetic properties Cristal field splitting energy  o, Cristal Field Stabilization Energy  △ o  △ o t 2g egeg

Copyright © Houghton Mifflin Company. All rights reserved.20 | 38 Crystal Field Splitting

Copyright © Houghton Mifflin Company. All rights reserved.20 | 39 Crystal Field Splitting

Copyright © Houghton Mifflin Company. All rights reserved.20 | 40 High and Low Spin

Copyright © Houghton Mifflin Company. All rights reserved.20 | 41 Strong Field Ligand vs. Weak Field Ligand [Co(H 2 O) 6 ] 2+ [CoCl 4 ] 2-

Copyright © Houghton Mifflin Company. All rights reserved.20 | 42 [Co(H 2 O) 6 ] 2+ [CoCl 4 ] 2-

Copyright © Houghton Mifflin Company. All rights reserved.20 | 43 Effect of Ligands on the Colors of Coordination Compounds

Copyright © Houghton Mifflin Company. All rights reserved.20 | 44 Spectrochemical Series The nature of the ligand determines the magnitude of the crystal field splitting, Δ o

Copyright © Houghton Mifflin Company. All rights reserved.20 | 45 Magnetism Ferromagnetism Paramagnetism Diamagnetism Magnetic moment, µ=[n(n+2)] 1/2 n: # unpaired electron [Mn(H 2 O) 6 ] 2+ µ=5.9 vs. [Mn(CN) 6 ] 4- µ= 2.2

Copyright © Houghton Mifflin Company. All rights reserved.20 | 46 Strong field Weak field Hund’s Rule strong paramagnetic

Copyright © Houghton Mifflin Company. All rights reserved.20 | 47 Magnetic Properties Paramagnetism illustrated:

Copyright © Houghton Mifflin Company. All rights reserved.20 | Chemical Reactions Ligand Exchange [Cu(H 2 O) 4 ] NH 3  [Cu(NH 3 ) 4 ] H 2 O K=4x10 8 [Ni(NH 3 ) 6 ] en  [Ni(en) 3 ] 2+ +6NH 3 Chelate effect (entropy) K=5x10 9

Copyright © Houghton Mifflin Company. All rights reserved.20 | 49 3 min. 1 day [Cr(H 2 O) 6 ] 3+ 3 min. 1 day [CrCl 2 (H 2 O) 4 ] + [CoCl 4 ] - [Co(H 2 O) 6 ] 2+ Labile complexes: exchange ligands rapidly Inert complexes: exchange ligands slowly

Copyright © Houghton Mifflin Company. All rights reserved.20 | 50 Electron transfer reaction

Copyright © Houghton Mifflin Company. All rights reserved.20 | 51 Problems 4, 26, 34, 38, 40, 60, 64, 72