FIVEFOLD BONDING IN CR(I) DIMER
“Synthesis of a Stable Compound with Fivefold Bonding Between Two Chromium(I) Centers” by
Tailuan Nguyen, Andrew D. Sutton, Marcin Brynda, James C. Fettinger, Gary J. Long, and Philip
P. Power, Science 310, 844-847 (2005).
1. Draw the Lewis structure for the Ar' ligand used in this paper. Keep in mind that the ligand is
anionic with a 1- charge.
2. (a) Draw the MO energy diagram for an isolated [Cr2
]
2+
molecule assuming the interactions of
only the 3d orbitals. (b) Next to each energy level, draw pictures of the molecular orbitals.
© Label each MO with the appropriate symmetry labels from the D∞h
character table. (d)
Fill in the correct number of valence orbitals, write the ground state electronic configuration,
and determine the bond order of the dimer. (e) Finally, how would your MO diagram change
if you lower the symmetry from D∞h
to C2h
?
3. Using the MO diagram from question 3, fill in the correct number of electrons and determine
the bond order for [Fe2
]
2+
and [Co2
]
2+
. Explain the importance of Ar'FeFeAr' and Ar'CoCoAr'
to the discussion of the bonding in Ar'CrCrAr'.
4. Some skeptics might argue that the planar trans-bent core geometry disproves the existence of
a quintuple bond. Describe what their argument might be
PLEASE HELP. Anything would be appreciated
