Lecture #31
  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 Transition metal complexes

Structural Isomers


Geometrical isomers

Square planar geometries

Octahedral geometries

Optical isomers

Observations to explain


Magnetic Properties


Crystal Field Theory

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.

The octahedral arrangement symbolized by Ma2b2c2 where the three pairs of ligands are all "cis" with respect to each other has two optical isomers.
The previous structure rotated so as to match up the ligand pairs b and b with that of the mirror image, also matching up one of the a ligands. The two structures are not superimposible meaning that they then must be optical isomers.
The octahedral complex Ma2b2c2 in which the ligands are all "trans" to each other is a geometrical isomer of the "cis" arrangement. Its mirror image will be superimposible and therefore there are no optical isomers of this structure.
The mirror image of the previous complex
The two structures (original + mirror image) are identical.
The electron configuration of the transition metal ion Co3+
Light absorption properties of some Co3+ complex ions
Magnetic properties of some Co3+ ions
Geometrical properties of some transition metal ions.
Crystal field theory addresses all the "puzzles" from the previous lecture.
Developing the idea of crystal field theory..
Following what happens to the outer d-orbitals when a transition metal ion is placed in a spherically distributed negative charge, and then one that has octahedrally deployed negative charges.
The weak field splitting and strong field splitting of the d-orbitals illustrated.
You need to know the relative crystal field strengths of a restricted number of ligands indicated here.
The electron configuration in the weak field complex CoF63- and the strong field complex Co(NH3)63+.