Given the values for ? below and the Jorgensen f - and g -values below, 1. appro
ID: 980364 • Letter: G
Question
Given the values for ? below and the Jorgensen f- and g-values below,
1. approximate CFSE
2. show the appropriate CF diagram for the metal complexes in the following compounds.
a) K3[Ru(C2O4)3].2H2O (Take g to be ca. 27.0; ? ? 22,000 cm-1)
b) Al[Mn(CN)6] (take g to be 16.0 and ? as 25,200 cm-1)
f factors g factors 3d5 Mn(II) 8.0 3d8 Ni (lI) 8.7 3d7 Co(I) 9.0 3d3 V(II) 12.0 3d5 Fe(III) 14.0 3d3 Cr(llI) 17.4 3d6 Co(lIl) 18.2 3d9 Cu(l) 9.5 3d4 Cr(ll) 9.5 4d6 Ru(lI) 20.0 3d3 Mn(IV) 23.0 3d3 Mo(III) 24.6 4d6 Rh(IIl) 27.0 4d3 Tc (IV) 30.0 5d6 Ir(II) 32.0 5d6 Pt(lV) 36.0 Br SCN Cl oxalate2- H2O NCS CH3CN pyridine NH 0.72 0.73 0.78 0.83 0.90 0.99 1.00 1.02 1.22 1.23 1.25 en (ethylenediamine) bipy (2,2' -bipyridine) 1.28 1.33 1.34 Phen (1:10-phenanthroline CN 1.70Explanation / Answer
When one electron occupies one of the lower energy levels, it has been stabilized (compared to the
average energy of all five orbitals by one the x (fraction) x o. This is called the crystal field stabilization energy
or CFSE and is + because of the name “stabilization energy.” The change in energy is negative and simply
given by E = –CFSE. Thus, electronic structures with electrons in the lower energy levels and not the upper
energy levels have a + CFSE and have E < 0.
The binding ability of the ligand affects o. Ligands that bind strongly increase the size of o and are called
“strong field ligands.” Weak field ligands do not increase the size of o. All ligands can be listed in an order
called the spectochemical series.
Spectochemical Series:
I- < Br- < SCN- < Cl- < F- < OH- < ox < H2O < NCS- < py , NH3 < en < bpy < NO2- < CH3- < CN- < CO
Weak field ligands … Strong field ligands
High-spin complexes … Low-spin complexes
The metal’s and the ligand’s contributions to estimating o can be summarized in Jorgensen’s relationship,
o = f x g. The f-factor follows the spectrochemical series. The units are in “wavenumbers” — 1000 cm-1.
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