COORDINATION CHEMISTRY STRUCTURES AND ISOMERS - PowerPoint PPT Presentation

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COORDINATION CHEMISTRY STRUCTURES AND ISOMERS

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  1. COORDINATION CHEMISTRY STRUCTURES AND ISOMERS

  2. ELECTRONIC CONFIGURATION Ground State: Progressive filling of the 3d, 4d, and 5d orbitals Exceptions: ns1 (n-1)d5 rather than ns2 (n-1)d4 ns1 (n-1)d10 rather than ns2 (n-1)d9 Transition metal ions: First in first out

  3. TRENDS - IONIC Radii

  4. COORDINATION COMPOUNDS • Coordination compounds – compounds composed of a metal atom or ion and one or more ligands. • [Co(Co(NH3)4(OH2)3]Br6 • Ligands usually donate electrons to the metal • Includes organometallic compounds Werner’s totally inorganic optically active compound.

  5. WERNER’S COORDINATION CHEMISTRY • Performed systematic studies to understand bonding in coordination compounds. • Organic bonding theory and simple ideas of ionic charges were not sufficient. • Two types of bonding • Primary – positive charge of the metal ion is balanced by negative ions in the compound. • Secondary – molecules or ion (ligands) are attached directly to the metal ion. • Coordination sphere or complex ion. • Look at complex on previous slide (primary and secondary)

  6. WERNER’S COORDINATION CHEMISTRY • He largely studied compounds with four or six ligands. • Octahedral and square-planar complexes. • It was illustrated that a theory needed to account for bonds between ligands and the metal. • The number of bonds was commonly more than accepted at that time. • 18-electron rule. • New theories arose to describe bonding. • Valence bond, crystal field, and ligand field.

  7. COORDINATION COMPOUNDS

  8. COORDINATION COMPOUNDS

  9. LIGANDS

  10. LIGANDS

  11. LIGANDS

  12. CHELATING LIGANDS trisoxalatochromate(III) ion or just [Cr(ox)3]3- • Chelating ligands (chelates) – ligands that have two or more points of attachment to the metal atom or ion. • Bidentate, tridentate, tetra.., penta…, hexa… (EDTA).

  13. A HEXADENTATE LIGAND, EDTA • There are six points of attachment to the calcium metal. • Octahedral-type geometry ethylene diamine tetraacetic acid (EDTA) ethylenediaminetetraacetatocalcium ion or just [Ca(EDTA)]2-

  14. LIGANDS

  15. NOMENCLATURE • Coordination compounds that are ionic, the cation is named first and separated by a space from the anion, as is the case for all ionic compounds. The names of neutral coordination complexes are written without spaces. Na[PtCl3(NH3)] Sodium amminetrichloroplatinate(II) K2[CuBr4] Potassium tetrabromocuprate(II)

  16. NOMENCLATURE trans-[Co(en)2I(H2O)](NO3)2 trans-aquabis(ethylenediamine)iodocobalt(III) nitrate mer-[Ru(PPh3)3Cl3] mer-trichlorotris(triphenylphosphine)ruthenium(III)

  17. NOMENCLATURE • The name of the coordination compound (neutral, cationic or anionic) begins with the names of the ligands. The metal is listed next, following in parentheses by the oxidation state of the metal.

  18. NOMENCLATURE When more than one of a given ligand is bound to the same metal atom or ion, the number of such ligands is designated by the following prefixes: 2 di 6 hexa 10 deca 3 tri 7 hepta 11 undeca 4 tetra 8 octa 12 dodeca 5 penta 9 nona

  19. NOMENCLATURE However, when the name of the ligand in question already contains one of these prefixes or ligands with complicated names (generally ligand names that are three syllables or longer), then a prefix from the following list is used instead: 2 bis 6 hexakis 3 tris 7 heptakis 4 tetrakis 8 octakis 5 pentakis 9 ennea

  20. NOMENCLATURE Neutral ligands are given the same name as the uncoordinated molecule, but with spaces omitted. Some examples are: (CH3)3SO dimethylsulfoxide (DMSO) (NH2)2CO urea C5H5N pyridine terpy terpyridine bpy 2,2’-bipyridine en ethylenediamine PCl3 trichlorophosphine PPh3 triphenylphopshine

  21. NOMENCLATURE EXCEPTIONS: Some neutral molecules, when serving as ligands are given special names. These are: NH3 ammine H2O aqua NO nitrosyl CO carbonyl CS thiocarbonyl

  22. NOMENCLATURE • Anionic ligands are given names that end in the letter “o”. When the name of the free, uncoordinated anion ends in “ate”, the ligand name is changed to end in “ato”. Some examples are : CH3CO2- (acetate) acetato SO42- (sulfate) sulfato CO32- (carbonate) carbonato acac acetylacetonato

  23. NOMENCLATURE When the name of the free, uncoordinated anion ends in “ide”, the ligand name is changed to end in “ido”. Some examples are: N3- (nitride) nitrido N3- (azide) azido NH2- (amide) amido

  24. NOMENCLATURE When the name of the free, uncoordinated anion ends in “ite”, the ligand name is changed to end in “ito”. Some examples are: NO2- (nitrite) nitrito SO32- (sulfite) sulfito ClO3- (chlorite) chlorito

  25. NOMENCLATURE Certain anionic ligands are given special names, all ending in “o”: CN- cyano F- fluoro Cl- chloro Br- bromo I- iodo O2- oxo O2- superoxo OH- hydroxo H- hydrido CH3O- methoxo

  26. NOMENCLATURE The ligands are named alphabetically, ignoring the prefixes bis, tris, etc…

  27. NOMENCLATURE When the coordination entity is either neutral or cationic, the usual name of the metal is used, followed in parentheses by the oxidation state of the metal. However, when the coordination entity is an anion, the name of the metal is altered to end in “ate”. This is done for some metals by simply changing the ending “ium” to “ate”: Scandium scandate Titanium titanate Chromium chromate