The compound ArGa[Co(CO)4]2 (Ar=C6H3[CH2N(CH3)2]2) presents an
interesting case of structural disorder. Commonly disorder is encountered among terminal chemical groupsof a metal complex,
e.g. phenyl, t-butyl, or trifluoromethyl. But in this complex the central metal is disordered instead. The disorder arises from
an oversize central cavity (produced by the two bulky Co(CO)4 groups) that allows the smaller
gallium cation to "rattle" around. Early stages of structure refinement show a five-coordinate non-disordered
gallium ion at the center. Further refinement, however, yields an elongated gallium thermal ellipsoid and
a nearby difference map peak indicative of disorder. NMR measurements to liquid nitrogen temperature show equivalence
of the terminal methyl protons is maintained from room temperature, thus indicating that the disorder is dynamic and rapid, relative to the NMR
time scale, even at low temperature.
Literature reference: Olazabal, C. A., Gabbai, F. P., Cowley, A. H., Carrano, C. J.,
Mokry, L. M., and Bond, M. R. "Intermolecular Base Stabilization of Cobalt-Gallium and
Cobalt-Indium Compounds" Organometallics 1994, 13, 421-423.
Companion Structure: ArIn[Co(CO)4]2
Structure Determination Files by FTP
Download X-ray Data Set (co1c.hkl)
Download X-ray Data Collection Parameters (co1c.p4p)
Download Final Refinement Results (co1c.res)
Last changed December 4, 1996
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