Metal Complexes Past Paper PDF

第1３回 ★ 金属錯体の基礎 後半 ブラディ・ジャスパーセン一般化学 （下）21章 配位数と幾何構造  Coordination Number (CN) ▪ Number of bonds formed by metal ions to ligands in complex ions ▪ Varies from 2 to 8 ▪ Depends on:...

第1３回 ★ 金属錯体の基礎 後半 ブラディ・ジャスパーセン一般化学 （下）21章 配位数と幾何構造  Coordination Number (CN) ▪ Number of bonds formed by metal ions to ligands in complex ions ▪ Varies from 2 to 8 ▪ Depends on: 配位数 1. Size of central atom 2. Steric interactions of ligands 3. Electrostatic interactions e.g. [Co(NH3)6]3+ CN = 6 [PtCl4]2− CN = 4 Ni(CO)4 CN = 4 CN 4 and 6 most common Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 3  金属錯体構造の予測 金属錯体の金属原子＝部分的に満たされたｄ軌道 ➝ VSEPRモデルが適用できない 一般には、金属錯体の構造予測にVSEPRは用いない ➝ 満たされたｄ軌道の場合には適用可 例）Ag+ = 満たされたｄ軌道 →VSEPRモデル適用可 Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 4  Structures CN = 2 ML2 Linear H3N Ag NH3 + − NC Ag CN CN = 6 ML6 Octahedral Cl 3− OH2 2+ Cl Cl H2O OH2 Cr Ni Cl Cl H2O OH2 Cl OH2 Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 5  Octahedral（八面体） ML6 Octahedral 正八面体 Cl 3− OH2 2+ Cl Cl H2O OH2 Cr Ni Cl Cl H2O OH2 Cl OH2  Structures CN = 4 ML4 Tetrahedral NH3 2+ CO Zn Ni NH3 CO H3N NH3 OC CO CN = 4 ML4 Square Planar − NH3 2+ NC CN 2 H3N Ni Cu NC CN H3N NH3 Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 7  Tetrahedral（四面体） ML4 Tetrahedral 正四面体 NH3 2+ CO Zn Ni NH3 CO H3N NH3 OC CO  Isomers ▪ Existence of two or more compounds with same chemical formula and different physical properties ▪ Consider Cr・3Cl－·6H2O ▪ Can isolate three compounds with this formula ▪ Each with own characteristic color and distinct physical properties 1. [Cr(H2O)6]Cl3 purple 2. [Cr(H2O)5Cl]Cl2·H2O blue-green 異性体 3. [Cr(H2O)4Cl2]Cl·2H2O green Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 9  Coordination Isomers ▪ Results from interchange of anionic ligand in first coordination sphere with anion outside coordination sphere Ex. ① [Cr(NH3)5Br]SO4 violet ② [Cr(NH3)5(SO4)]Br red ▪ Easily distinguished by tests for counterion ① SO42–(aq) + Ba2+(aq) ⎯→ BaSO4(s) ② Br –(aq) + Ag+(aq) ⎯→ AgBr(s) 溶液中に自由に存在するカウンターイオンの反応性で確認できる. Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 10  Stereoisomerism 立体異性 ▪ Difference among isomers that arises from various possible orientations of atoms in space ▪ Same atoms attached, but in different order in space ▪ Two major types 1. Geometric isomerism 2. Chirality or handedness （掌性） 配位子の空間的配置関係の相違. Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 11  1. Geometric Isomerism CN = 4 Square planar 平面四配位 ▪ trans- and cis- isomers trans- ▪ Occurs only with ML2X2 （反対側に） H3N Cl Pt ▪ trans- isomer Cl NH3 ▪ Opposite each other cis- （同じ側に） ▪ cis- isomer H3N Cl Pt ▪ Next to each other H3N Cl Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 12  Chirality ▪ More subtle form of structural isomerism ▪ Differ only in “handedness” ▪ Right glove doesn’t fit left hand ▪ Mirror-image object is different from original object 鏡像 Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 13  Superimposable Chiral ▪ Object and its mirror image are NOT superimposable Enantiomers ▪ Two non-superimposable isomers e.g. [Co(en)3]2+ 鏡像異性体➝重ね合わせできない Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 14  Geometric Isomers Not Necessarily Optical Isomers M(LL)2X2 ▪ Two bidentate ligands and two monodentate ligands ▪ cis- isomer has two optical isomers ▪ Chiral with two enantiomers 鏡像異性体 mirror + + N N N Cl Cl N Co Co N Cl Cl N N N l- cis d-cis Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 15  Geometric Isomers Not Necessarily Optical Isomers M(LL)2X2 ▪ Two bidentate ligands and two monodentate ligands ▪ Trans-isomer has no optical isomers ▪ Not chiral mirror Cl + Cl + N N N N Co Co N N N N Cl Cl trans Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 16  Unpolarized and Polarized Light ▪ Light possesses electric and magnetic components that behave like vectors ▪ In unpolarized light, electromagnetic oscillations of photons oriented at random angles perpendicular to axis of light propagation Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 17  How to Determine Chirality ▪ Place solution in polarimeter and pass plane polarized light through it ▪ Enantiomers rotate plane-polarized light in opposite directions levo-rotatory=左旋性(−) dextro-rotatory=右旋性(+) Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 18  Isomerism, Chirality Chiral or Optical Isomers ▪ Most important occurs in octahedral geometry ▪ [M(LL)3]n+ N N N N N N Co Co N N N N N N levo-rotatory=左旋性(−) dextro-rotatory=右旋性(+) l- isomer d- isomer Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 19 結晶場と物性  Crystal Field Theory ▪ Localized electron model doesn’t work ▪ No information about how energies of d orbitals are affected by ligands when they form 1.Transition metal complexes are usually colored ▪ Different ligands often give different colors Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 21  Crystal Field Theory 2. Magnetic properties of transition metal complexes often affected by what ligands are attached to metal ▪ Because transition metals have incomplete d subshells, complexes often paramagnetic ▪ But for given metal, number of unpaired spins varies e.g. [Fe(H2O)6]2+ four of its six 3d electrons are unpaired; [Fe(CN)6]4– has no unpaired spins ▪ Any theory that attempts to explain bonding in transition metal complexes must account for color and magnetic properties Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 22  Crystal Field Theory ▪ It is important what directions orbitals point ▪ Three point in between the two axes (x, y, and z) that are their label ▪ dxy, dxz, and dyz ▪ Other two point along the axis named in their label ▪ dx2 – y2 , & dz2 dxy dxz dyz dx2 – y2 dz2 Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 23  Crystal Field Theory ▪ Now construct octahedral metal complex using this coordinate system ▪ Metal at origin ▪ Ligands coming in along positive and negative x, y, and z axes ▪ “What is effect of point negative charges on energies of partially filled d orbitals?” Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 24  Octahedral Crystal Field Splitting ( d x2 – y2, dz2) エネルギー縮退 (dxy, dxz, dyz) ▪  = Crystal field splitting = h = hc/ ▪ Splitting of d orbitals leads to magnetic properties ▪ Magnitude of  depends on ligand and metal Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 25  Spectrochemical Series ▪ Ligand that produces large  with one metal produces large  with other metals ▪ Ligands arranged in order of their effectiveness in producing large crystal field splitting ▪ Spectrochemical Series 分光化学系列 ▪ Common ligands in decreasing  strength ▪ CH3– ~CO > CN– > NO2– > en > NH3 > H2O > C2O42– > OH– > F– > Cl– > Br– > I– ▪ With same metal, １９３８年 槌田先生が発表 ※VSEPRの発見者 ▪ CO produces largest  ▪ I– produces smallest  Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 26  Using Crystal Field Theory ▪ Can use d orbital splitting to explain relative stabilities of oxidation states of metals Ex. Cr2+ easily oxidized to Cr3+ in [Cr(H2O)6]2+ and [Cr(H2O)6]3+ ▪ To explain, look at electron configurations ▪ Cr = [Ar]3d 5 4s1 （価電子数＝6） ▪ For Cr2+ remove two electrons ▪ Cr2+ = [Ar]3d 4 ▪ For Cr3+ remove three electrons ▪ Cr3+= [Ar]3d 3 Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 27  Using Crystal Field Theory ▪ Put electrons into d orbitals using Hund’s Rule dx2 – y2 dz 2 ▪ With Cr2+ we have choice ▪ Experimentally find fourth e– dxy dxz dyz goes into higher energy d set Cr2+ = [Ar] 3d 4 ▪ Cr3+ only has three electrons; all go into lower energy set of d orbitals dx2 – y2, dz2 ▪ Oxidizing Cr2+ means removing an electron from dxy dxz dyz higher energy orbital, leaving a lower energy complex Cr3+ = [Ar] 3d 3 Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 28  Absorption of Light ▪ E = h = hc / =  ▪ When photon of light is same energy as spacing between d levels, ▪ Light absorbed ▪ Electron transfers from dxy, dyz, or dxz orbital to dx 2 – y2 or dz orbital 2 Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 29  Color Wheel ▪ Green-blue is complementary color to red ▪ Yellow is complementary color to violet-blue ▪ If substance absorbs given color when bathed in white light ▪ Perceived color of reflected or transmitted light is complementary color Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 30  Absorption of Light [Cr(H2O)6]3+ ▪ When an electron moves from one set of d orbitals to other ▪ Absorbs light = 575 nm (yellow light) ▪ Transmits violet, so solution appears violet Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 31  Effect of Ligand on  ▪ Color absorbed depends on magnitude of  高エネルギー吸収 ▪ As  increases, energy of ＝blue h increases, and frequency of light increases ▪ For transition metals with same oxidation state,  depends on ligand [Cr(H2O)6]2+ [Cr(NH3)6]2+ NH3 induces larger  than H2O [Cr(NH3)6]2+ absorbs higher energy light than [Cr(H2O)6]2+ [Cr(NH3)6]2+ absorbs blue light so appears orange-yellow Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 32  Using Crystal Field Theory ▪ Cr2+ has d 4 electron configuration どっちが安定？ Pairing Energy = P （スピン対形成エネルギー） ▪ Energy required to overcome Coulombic repulsion of putting two electrons in one orbital Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 33  Using Crystal Field Theory ▪ Where does fourth electron go? ▪ May enter higher d level ▪ Cost is  ▪ Which Occurs? ▪ Depends on magnitude (size) of  スピン対形成 ▪ If  > P ▪ then most stable is pair of electrons in lower d level スピン対つくらない ▪ If  < P ▪ then most stable is to put fourth electron in higher d level Jespersen/Hyslop, Chemistry7E, Copyright © 2015 John Wiley & Sons, Inc. All Rights Reserved. 34  Using Crystal Field Theory Ex. [Cr(H2O)6]2+ vs. [Cr(CN)6]4– ▪ CN– is strong field ligand ▪ >P fourth electron pairs up in lower level ▪ H2O is relatively weak field ligand ▪ 