1. Spectrochemical Series: Cr 3+ Safety: –Aqueous Cr 3+ complexes – dispose in liquid waste bottle. –Ligands: en, acacˉ, NO 3 ˉ, Clˉ, NH 3, H 2 O Lab management –Time is of the essence!!! Ligands (Urea is source of NH 3 ) (acacˉ is a bidentate ligand)

2. Spectrochemical Series: Cr 3+ What three factors affect the crystal field splitting of d-orbitals? Ligands: halides < OH - < C 2 O 4 2- < H 2 O < NCS - < py < NH 3 < en < phen < NO 2 - < CN - < CO Geometry(  T ~ 4/9  O ) (octahedral, tetrahedral, tetragonal, square planar, square pyramidal, trigonal prismatic) Nature of the transition metal (1) 3d vs 4d vs 5d (2) higher oxidation state vs lower oxidation state (3) other Mn 2+ < Ni 2+ < Co 2+ < Fe 2+ < V 2+ < Fe 3+ < Co 3+ < Mn 4+ < Mo 3+ < Rh 3+ < Ru 3+ < Pd 4+ < Ir 3+ < Pt 4+

3. Crystal field splitting

4. Origin of diagram Possible transitions Selection rules –Spin (superscript)  S = 0 –Symmetry (g vs u) no change (g→g) Tanabe-Sugano d 3

5. Two allowed, one forbidden transition

6. Assigning transitions (blue arrow reproduces observed transitions)

7. Spectrochem series: Cr 3+ E = hc/ = h  = hc –Energy in units of wavelength, frequency, and wavenumbers ~

8. Rule of average environment CrCl 2 (H 2 O) 4 + vs CrCl 6 3- Cr(H2O) 6 3+ Crystal field gap is a weighted average of those of the homoleptic (single type of ligand) complexes.

9. Beer’s law Saturation effects – avoid them by working at A < 0.25 Guts of a spectrophotometer (source, grating, sample, detector)