"Transition metal chemistry - Download as PowerPoint"
Review of variable valence Transition metal ions have variable oxidation state Electron configurations 4s23dn with some exceptions Isomerism – same atoms, different arrangement 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) 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 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- CoNH Br SO 3 5 4 CoNH SO Br 3 5 4 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 Octahedral complex 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) More than two ligands… ML2XY or ML4XY can also have cis and trans isomers Isomers or equal? 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 Testing for chirality Presence of planes of symmetry – achiral Absence of plane of symmetry – chiral Handedness in complexes with bidentate ligands How many diastereoisomers and enantiomers are there of Co(en)2Cl2+? Getting a complex? Which are chiral? Which are achiral? What are the enantiomers?