Chemistry 153 – Advanced Inorganic Chemistry Problem Set 4 (due ...

Chemistry 153 – Advanced Inorganic Chemistry
Problem Set 4 (due 3 February, 2012)
1. The absorption maxima of the 1 A 1 1 T 2 (t 1 e) bands in MO 4 n ions correlate with the force constants
for the symmetric M‐O stretching vibration (f M‐O ) as shown in the graph below.
a. Use your molecular orbital bonding model for MO 4 n to rationalize the trends across rows of the
periodic table.
b. Use your MO model to rationalize the trends among the three rows of the periodic table.
c. Which tetraoxo complex is likely to have the most negative charge on its oxygen ligands
Explain your reasoning.
d. Which tetraoxo complex is likely to have the least negative charge on its oxygen ligands
Explain your reasoning.
2. In 1953, Jack Dunitz and Leslie Orgel (J. Chem. Soc. 1953, 2594‐2596) proposed a molecular orbital
model to describe the metal‐metal interactions in linear oxo‐bridged (L 5 MOML 5 ) metal complexes
with D 4h symmetry. This molecular structure can be considered a high
symmetry analogue of the “blue‐dimer” water oxidation catalyst
([(bpy) 2 (H 2 O)Ru III ORu III (OH 2 )(bpy) 2 ] 4+ ).
a. Construct an MO diagram for a D 4h , d 5 ‐d 5 , L 5 Ru III ORu III L 5 complex using
the following orbitals: two sets of five metal 4d‐orbitals, ten ligand σ‐
orbitals, and the oxo 2s, 2pσ, and two 2pπ orbitals.
b. Determine the term symbol for the ground electronic state.

c. The temperature dependence of the
magnetic susceptibility and magnetic
moment of the blue dimer are shown to the
right. Does the magnetic behavior of this
molecule agree with the prediction based on
your MO model If not, propose a
refinement to your model that will rationalize
the discrepancies.