chapter24_CoordinationCompound

chapter24_CoordinationCompound - Chapter 24 Complexes A...

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1 Chapter 24 Coordination Compounds 1 Complexes • A central metal atom bonded a group of molecules or to a group of molecules or ions is a metal complex . • If the complex bears a charge, it is a complex ion . • Compounds containing omplexes are oordination complexes are coordination compounds . 2 Complexes • The molecules or ions coordinating to the metal are the ligands . • They are usually anions or polar molecules. • They must contain lone pairs. 3 Coordination Compounds •M a ny coordination compounds are brightly colored. • Different coordination compounds from the same metal and ligands can give quite different
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2 Coordination Compounds • The central metal and the ligands directly bonded to it make up the coordination sphere of the omplex complex. 5 Coordination Compounds All molecules and ions within the sphere are put in brackets. Those “free” ions (that dissociate from the complex ion when dissolved in water) are put outside the brackets. 6 Coordination Compound 7 Metal-Ligand Bond • The bond is formed when the ligand donates oth electrons to be shared by the ligand and both electrons to be shared by the ligand and the metal. The ligands have nonbonding electrons. The metal has empty orbitals. • The bond is called coordinate covalent bond . 8
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3 Monodentate Ligands • Some ligands connect to the metal atom through one donor atom. hese are called • These are called monodentate ligands . 9 Polydentate Ligands • Some ligands have two or more donor atoms. • These are called polydentate ligands or chelating agents . • In ethylenediamine, NH CH CH NH , 2 2 2 2 represented here as en , each N is a donor atom. • Therefore, en is bidentate . 10 Polydentate Ligands thylenediaminetetraacetate Ethylenediaminetetraacetate, mercifully abbreviated EDTA, has six donor atoms. 11 12
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Chelating Agents • Chelating agents generally form more stable complexes than monodentate ligands. herefore they can render metal ions inactive • Therefore, they can render metal ions inactive without actually removing them from solution. • Phosphates are used to tie up Ca 2+ and Mg 2+ in hard water to prevent them from interfering with detergents. 13 Chelating Agents orphyrins are • Porphyrins are complexes containing a form of the porphine molecule shown at the right. portant biomolecules Important biomolecules like heme and chlorophyll are porphyrins. 14 Chelating Agents orphines (like Porphines (like chlorophyll a ) are tetradentate ligands. 15 Metal-Ligand Bond he coordination of the ligand The coordination of the ligand with the metal can greatly alter its physical properties, such as color, or chemical properties, such as ease of oxidation. 16
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This note was uploaded on 09/14/2009 for the course CHEM 105 taught by Professor Zhao during the Summer '08 term at IUPUI.

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chapter24_CoordinationCompound - Chapter 24 Complexes A...

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