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Slide 2 of 60 . Slide 3 of 60 . Slide 4 of 60 . Slide 9 of 60 . Slide 10 of 60 . Slide 11 of 60 . Common Ligands. Monodentate. Contain only one donor atom Examples: H 2 O, CN - , NH 3 , NO 2 - , SCN - , OH - , X - , CO, O -2. Bidentate Contain 2 donor atoms

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  1. Slide 2 of 60

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  4. Slide 9 of 60

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  6. Slide 11 of 60

  7. CommonLigands • Monodentate • Contain only one donor atom • Examples: H2O, CN-, NH3, NO2-, SCN-, OH-, X-, CO, O-2 • Bidentate • Contain 2 donor atoms • Examples: oxalate (ox), C2O4-2, ethylenediamine (en), NH2CH2CH2NH2

  8. Common Ligands • Polydendate • Contain more than 2 donor atoms • Example: ethylenediaminetetraacetate ion (edta4-)

  9. Nomenclature of Coordination Compounds: IUPAC Rules • Cation named before anion for ionic compounds • When naming complexes: • Ligands are named first alphabetically • Metal atom/ion is named last • Oxidation state given in Roman numeral follows in parentheses

  10. Nomenclature: IUPAC Rules • Names of anionic ligands end with –o • Change –ide to –o • Change –ite to –ito • Change –ate to –ato • Examples of anionic ligands Bromide (Br-) becomes bromo Chloride (Cl-) becomes chloro

  11. Nomenclature: IUPAC Rules Cyanide (CN-) becomes cyano Hydroxide (OH-) becomes hydroxo Oxide (O2-) becomes oxo Nitrite (NO2-) becomes nitrito (M-O bond) or nitro (M-N bond) Carbonate (CO32-) becomes carbonato Oxalate(C2O42-)(?), SO42- (?), S2O32- (?)

  12. Nomenclature: IUPAC Rules • Neutral ligands referred to by their usual names • Example: ethylenediamine • Exceptions: Water (aqua) NH3 (ammine) CO (carbonyl)

  13. Nomenclature: IUPAC Rules • Number of each type of ligand in a complex is indicated by Greek prefixes: di-, tri-, tetra-, penta-, hexa- • If the name of the ligand begins with/contains a Greek prefix, use prefixes: bis-,2; tris-,3; tetrakis-,4; pentakis-,5; hexakis-,6.

  14. Nomenclature: IUPAC Rules • If complex is an anion, the name ends with –ate apended to either the English or Latin name of the metal. Examples: Scandium, Sc = Scandate Titanium, Ti = Titanate Vanadium, V = Vanadate Chromium, Cr = Chromate Manganese, Mn = Manganate

  15. Nomenclature: IUPAC Rules Iron, Fe = Ferrate Cobalt, Co = Cobaltate Nickel, Ni = Nickelate Copper, Cu = Cuprate Zinc, Zn = Zincate

  16. Square planar

  17. Isomerism in Coordination Compounds Isomers Compounds with the same molecular formula but different arrangement of atoms in space Constitutional Isomers Differ in how the atoms are joined together. (Ex. Ethanol and Dimethyl ether) Stereoisomers Have the same atoms bonded to each other but different spatial arrangements

  18. Constitutional Isomers Ionization Isomers Differ in an anion bonded to the metal Ex.: [Co(NH3)5Br]Cl vs [Co(NH3)5Cl]Br Linkage Isomers Differ in an atom of a ligand bonded to the metal Ex.: [Co(NH3)5(SCN)]Cl vs [Co(NH3)5(NCS)]Cl [Co(NH3)5(ONO)]Cl vs [Co(NH3)5(NO2)]Cl

  19. Stereoisomers Stereoisomers Have same atoms bonded to each other but different spatial arrangements Diastereomers (Geometric Isomers) Not mirror images and nonsuperimposable Enantiomers Mirror images but not superimposable

  20. Diastereomers Pt(NH3)2Cl2

  21. Diastereomers • Diastereomers have different chemical and physical properties • Different colors, melting points, polarities, solubilities, chemical reactivities, etc.

  22. Enantiomers (Optical Isomers) • Have the same chemical and physical properties • Except: • Optical activity • Reactivity toward “chiral” reactants

  23. Bonding in Coordination Compounds • Differences between transition metal complexes and representative metal complexes: • Transition metal complexes usually have color which is dependent on ligand, whereas representative metal complexes are colorless. • Electronic configuration (magnetic properties) of transition metals are affected by the ligands bonded to the central atom, whereas those of representative metals are not.

  24. Bonding in Coordination Compounds • Our understanding of these differences is based on two theories: • Valence Bond Theory • Crystal Field Theory

  25. Valence Bond Theory • A covalent bond forms between two atoms when an orbital on one atom overlaps with the orbital on another atom • Total number of electrons on both orbitals is no more than two.

  26. Valence Bond Theory • In transition metal complexes, covalent bonds are formed via overlap of a completely filled ligand orbital and a vacant hybrid orbital on metal ion. • Hybridization determines the geometry of the molecule If geometry is known, the hybrid orbitals of the metal ion used in the bonding is known.

  27. Valence Bond Theory Hybrid orbitals for common geometries in complexes CN Geometry Hybrid orbitals 2 linear sp 4 tetrahedral sp3 4 square planar dsp2 6 octahedral d2sp3, sp3d2

  28. Spectrochemical Series • Different ligands can be arranged in order of their abilities to produce a splitting of the d energy levels. This arrangement is known as spectrochemical series: CN- >NO2->en >py , NH3 >H2O >SCN- >OH- >F- >Cl->Br-> I- Strong field, large Δ weak field, small Δ

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