Lecture #32
Text: Chapter 19, Sections 1, 3, 4.
  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 metals

Transition metal complexes


Geometrical isomers

Square planar geometries

Octahedral geometries

Oxidation number rules continued. The rest of the main group elements are covered by this rule.
An oxidation number illustration of a salt in which the structures of both ions is known and therefore treated independently when assigning the oxidation numbers. The computer-generated structures on the right show the computer-generated electrostatic charges actually at the different nuclei, thus illustrating that oxidation numbers are an extreme intrepretation of the effect of electronegativity differences on electron deployment.
Oxidation numbers need not be integers!!
Leaving the representative 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
Donor atom illustration
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.
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.