Thirteen-Vertex Metallocarboranes

The first supraicosahedral monometallocarborane was prepared by polyhedral expansion of 1,2-C2B10Hi2 with C0CI2 and C5H5 (17,18)  

Three isomeric complexes of this formula have been prepared, which are 

The structure of the red isomer of C5H3C0C2B10H12 (Fig. 14), determined by Churchill (8), indicated that the complex was asymmetric, although nB NMR spectroscopy indicated mirror symmetry for this species in solution at room temperature. Low-temperature nB NMR spectral investigations showed that the molecule was fluxional in solution at room temperature. It has been postulated (18) that the complex undergoes rapid diamond-square-diamond rearrangement (Fig. 15) in which enantiomeric complexes interconvert. 

Thirteen-vertex complexes of metals other than cobalt have been prepared, as have commo thirteen-vertex anions and metal carbonyl derivatives (18). In general, these complexes exhibit stabilities similar to or less than their twelve-vertex counterparts. 

The chemistry of the thirteen-vertex monometallocarboranes, although less extensively studied, is similar to that of the twelve-vertex analogs. Thus, C5H6CoC2Bi Hi2 undergoes polyhedral subrogation to produce thirteen-vertex bimetallocarboranes [the metals may be identical (23) or 

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