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Review of variable valence

Review of variable valence. Transition metal ions have variable oxidation state Electron configurations 4s 2 3d n with some exceptions. Isomerism – same atoms, different arrangement. Constitutional and stereo. Constitutional Different connections between the atoms

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Review of variable valence

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  1. Review of variable valence • Transition metal ions have variable oxidation state • Electron configurations • 4s23dn with some exceptions

  2. Isomerism – same atoms, different arrangement

  3. Constitutional and stereo • Constitutional • Different connections between the atoms • Linkage isomers (choice of linkage atom) • Ionization isomers (different anion bonding) • Stereoisomers • Same connections but different spatial arrangements • Diastereoisomers (geometric isomers) • Enantiomers (handedness)

  4. Linkage isomers • The nitrite ion can use either the O or the N atom as the ligand since both have non-bonding pairs. • Indicate linkage in the name: • Nitro (NO2) links through N • Nitrito (ONO) links through O • Obvious influence on physical properties

  5. Ionization isomers • Different anions are linked to the central atom • In one, the free anion is SO42- • In the second, the free anion is Br-

  6. Diastereo (geometric) isomers • Same attachments but different arrangement • Cis- and trans- (analogous to bonding in alkenes) • Influences physical properties through different polarity • Example with square planar: opposite or side-by-side

  7. Octahedral complex

  8. Not all complexes qualify for geometric isomers • Square planar – • ML2X2 (cis and trans) • ML3X (none) • Tetrahedral – none with any composition • Octahedral – • ML4X2 (cis and trans) • ML3X3 • ML5X (none)

  9. More than two ligands… • ML2XY or ML4XY can also have cis and trans isomers

  10. Isomers or equal?

  11. What hands are these…? • Apparently all same connections and yet… • Enantiomers are molecules or ions that form mirror images of each other • Tetrahedral C atoms with four different groups • Hands are enantiomers. • They possess chirality • Molecules that have no handedness are achiral

  12. Testing for chirality • Presence of planes of symmetry – achiral • Absence of plane of symmetry – chiral

  13. Handedness in complexes with bidentate ligands

  14. How many diastereoisomers and enantiomers are there of Co(en)2Cl2+?

  15. Getting a complex? • Which are chiral? • Which are achiral? • What are the enantiomers?

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