Spectrochemical%20Series:%20Cr3

1
Spectrochemical Series Cr3

• Safety
• Aqueous Cr3 complexes dispose in liquid waste
  bottle.
• Ligands en, acac, NO3 , Cl, NH3, H2O
• Lab management
• Time is of the essence!!!
• Ligands

(Urea is source of NH3)
(acac is a bidentate ligand)
2
Spectrochemical Series Cr3

• What three factors affect the crystal field
  splitting of d-orbitals?

Geometry (DT 4/9 DO) (octahedral, tetrahedral,
tetragonal, square planar, square pyramidal,
trigonal prismatic)

• Ligands
• halides lt OH- lt C2O42- lt H2O lt NCS- lt py lt NH3 lt
  en lt phen lt NO2- lt CN- lt CO

Nature of the transition metal (1) 3d vs 4d vs 5d
(2) higher oxidation state vs lower oxidation
state (3) other Mn2 lt Ni2 lt Co2 lt Fe2 lt V2
lt Fe3 lt Co3 lt Mn4 lt Mo3lt Rh3 lt Ru3 lt Pd4 lt
Ir3 lt Pt4
3
Crystal field splitting
4
Tanabe-Sugano d3

• Origin of diagram
• Possible transitions
• Selection rules
• Spin (superscript)
• DS 0
• Symmetry (g vs u)
• no change (g?g)

5
Two allowed, one forbidden transition
6
Assigning transitions(blue arrow reproduces
observed transitions)
7
Spectrochem series Cr3

• E hc/l hn hcn
• Energy in units of wavelength, frequency, and
  wavenumbers

8
Rule of average environment

• CrCl2(H2O)4 vs CrCl63-
• Cr(H2O)63
• Crystal field gap is a weighted average of those
  of the homoleptic (single type of ligand)
  complexes.

9
Beers law

• Saturation effects avoid them by working at A lt
  0.25
• Guts of a spectrophotometer
• (source, grating, sample, detector)