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Distorted <i>commo</i>-Cobaltacarboranes Based on the 5,6-Dicarba-<i>nido</i>-decaborane(12): The First Bimetal Cobalt鈥揅opper Zwitterion-Containing Cluster with Four (B鈥揌)<sub>4</sub>路路路Cu Bonds Not Showing Fluxional Behavior in Solution
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of a recently reported complex [Ph<sub>4</sub>P]颅[<i>closo,nido-</i>CoH颅(2,4-C<sub>2</sub>B<sub>8</sub>H<sub>10</sub>)颅(7,8-C<sub>2</sub>B<sub>8</sub>H<sub>11</sub>)] (<b>1</b>) either by H<sub>2</sub>O<sub>2</sub> in acetone or NaH in THF leads to the loss of
both the bridging and terminal hydrides yielding the diamagnetic salt
of an anionic <i>commo</i>-cobaltacarborane [Ph<sub>4</sub>P]颅[Co颅(2,4-<i>isonido</i>-C<sub>2</sub>B<sub>8</sub>H<sub>10</sub>)<sub>2</sub>] (<b>2</b>) with the {CoC<sub>2</sub>B<sub>8</sub>}-cluster units adopting a distorted skeletal geometry
of the <i>isonido</i>-type. The anionic <i>commo</i> complex <b>2</b> reacts with in situ generated cationic [CuPPh<sub>3</sub>]<sup>+</sup> species to give stable copper鈥揷obalt
zwitterion [Ph<sub>3</sub>PCu]颅[Co颅(2,4-<i>isonido</i>-C<sub>2</sub>B<sub>8</sub>H<sub>10</sub>)<sub>2</sub>] (<b>3</b>) with four two-electron, three-center (B鈥揌)<sub>4</sub>路路路Cu
bonds, and exhibits no fluxional behavior in solution. Complex <b>3</b>, at the same time, in CH<sub>2</sub>Cl<sub>2</sub> in the
presence of 2-fold excess of PPh<sub>3</sub> readily converts to a
new anionic species [(Ph<sub>3</sub>P)<sub>3</sub>Cu]颅[Co颅(2,4-<i>isonido</i>-C<sub>2</sub>B<sub>8</sub>H<sub>10</sub>)<sub>2</sub>] (<b>4</b>) which retains initial <i>isonido</i> geometry. All newly obtained diamagnetic <i>commo</i> complexes
were characterized by a combination of analytical and multinuclear
NMR spectroscopic data and by single-crystal X-ray diffraction studies
of complexes <b>2</b> and <b>3</b>
