Chem 1120 1st Edition Lecture 23 Outline of Last Lecture I. Transition Metal Properties and TrendsII. MagnetismIII. Coordination Complexes and LigandsOutline of Current Lecture I. Coordination Numbers and GeometryII. Chelates and Kinetic LabilityIII. NomenclatureIV. IsomerismCurrent LectureI. Coordination Number = number of ligands bonded directly to central metal ion or atom Coordination number is specific for a given metal in a particular oxida-tion state; governed by——> metal size, ligand size, ligand type, ligand chargeFor example, while iron(III) can bind to 6 fluorides, it can only gain 4 chlo-rides because the chlorides are larger than the fluorides Geometry/shape of a complex depends on coordination number and metal ionMost common coordination numbers are: 4 and 6Coordination number of 4: tetrahedral and square planarCoordination number of 6: octahedralWhat are the coordination numbers for the metal ions in the pictures to the right? These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Answer: 4 for both (theres 4 things attached) II. Many organic molecules have multiple donor atoms; chelate = a ligand bonded to a central metal atom at two or more points, for example, ethylenediamine (en) is a bidentate ligand meaning it is bonded to the metal atom in two pointsMore than two donor atoms make the ligand polydentate, for example, EDTA supplies at most 6 donorsBidentate and polydentate ligands are chelating agents, where the metal ion is geld tightly by ligandChelate Effect: increased stability and rate of formation for a metal complex because of polydentate ligands Coordination complexes can exchange inner sphere ligands, however, in de-termining reactivity, we must consider both thermodynamic stability and ki-netic labilityThermodynamic Stability: property of a compound with a large formation constant and thus a large negative ΔGKinetic Lability: the tendency to exchange ligands very quickly in solution; whether or not the compound is stable depends on how fast they exchange; the faster they exchange ligands, the less stable and vice versaIn biological systems, carbon monoxide (CO) and cyanide (CN-) are poi-sonous because they will bind more tightly to the iron than will oxygen III. Square brackets enclose the complex ion and counterions ions are out-side the brackets1. the cation is named before the anionNaCl ——> sodium chlorideK3[Fe(CN)6] ——> Potassium hexacyanoferrate (III)2. Ligands are named first, metals last 3. Ligands are named in alphabetical order4. Ligand names: anions end in -o; most neutral ligands are named as the molecule; exceptions: water = aqua, CO = carbonyl, ammonia = ammine5. Number of each ligand is indi-cated by Greek prefixes:6. Metal oxidation state is indicatedby Roman numerals; determiningoxidation state: Net charge = ΣM(charge) + L(charge)7. Anionic metal complex namesend in -ate; basically, if the netcharge on the complex is nega-tive, add ate to the end of themetal name:Answer: A IV. It’s possible to assemble a coordination complex in several different ways, which results in the formation of isomersIsomers = compounds with the same formulas but different arrangements of atoms 1. Structural Isomers = molecules have the same molecular formula, but arebonded together in different orders; 2 kinds:2. Coordination Sphere Isomers = composition within the brackets is ar-ranged differently3. Linkage Isomers = ligand is bound to the metal by a different atom4. Stereoisomers = have the same molecular formula and sequence of bonded atoms, but differ only in 3D orientation5. Geometric Isomers = have a restricted rotation somewhere in a molecule, usually just involve the carbon-carbon double bond; trans ——> atoms locked on opposite sides of the double bond, cis ——> atoms locked on the same side of the double bond6. Optical Isomers = molecules that are the mirror image, but cannot be su-perimposed Square planar and octahedral complexes can have cis or trans isomers, tetrahedral cannotStereoisomers: enantiomersd - dextrorotatory (right-handed)l - levorotatory