Lecture #31
This will move us to Chapter 19
  CURMUDGEON GENERAL'S WARNING. These "slides" represent highlights from lecture and are neither complete nor meant to replace lecture. It is advised not to use these as a reliable means to replace missed lecture material. Do so at risk to healthy academic performance in 09-105.
Lecture Outline Oxidation numbers

Transition Metal Chemistry

Tramsition metal ion electron configurations

Coordination complexes


  • Structural Isomers
  • Stereoisomers

Geometrical isomers

Leaving the Representative (Main Group) elements and looking at the transition elements brings us back to d-electrons.

Transition metal chemistry
Electron configurations of transition metal ions (which do not follow the conventional order, as you recall)
Third ionization energies: the energy necessary to remove a third electron from a transition metal. Why the drop at Z=26 (iron)?
Transition metal complex ions are transition metal ions surrounded to bound ligands
The compound shown is a salt, and if dissolved in a solvent (water) enables some revealing, simple experiments to be done that help recognize something about the molecule's structure. The experiments are usually one of two types: electrical conductivity and precipitation.
A bidentate ligand connects to the central species through two donor atoms from the same ligand.
Complex ions in compounds

VSEPR was used to determine geometries when central atoms were s and p block (main group) elements. VSEPR does not work well when addressing the geometry of d block (transition metal) elements. The geometries' we'll consider, though, are limited as this slide indicates.
After introducing the phenomenon of "waters of hydration" and, separately, recalling structural and geometrical isomerism, the following structural isomers were listed, all with the formula Cr(H2O)6Cl3.
Geometrical isomerism in octahedral complexes. The bonds are indicated by green lines. Geometrical isomer "trans" dichloro complex is on the left and a "cis" dichloro complex is on the right.
More observations about geometrical isomerism in octahedral complexes.
More observations about geometrical isomerism in octahedral complexes.
A class of isomers called "stereoisomers" consists of geometrical isomers, which we already have seen examples of, and "optical isomers", also called "enantiomers". Optical isomers are said to be "chiral" and have a distinction between them that is similar to the distinction between the left hand and the right hand.
A tetrahedral arrangement symbolized as Mabcd (four different ligands) consists of two possible optical isomers.