C2B3 Ring Double-decker Sandwiches

The B-halogenated derivatives, in turn, allow direct introduction of alkynyl and other functional groups desilyla-tion and linkage affords dimers linked by dialkynyl chains 5  

Species functionalized at boron, such as 50-53, have also been prepared from the corresponding MC2B4 closo clusters via the removal of the apex BH unit (decapitation) with I M Kl)A.54 57 The same approach has been employed to link CoC2B3 units to benzene or other arenes 5 As shown in the following subsection, di- and trinuclear complexes such as 53 and 54 are easily converted to multi-triple-decker sandwich systems. 

Organic functional groups can also be placed on the Cp ligands in CpMG2B3 complexes, e.g., 59,60 and this approach has been exploited to generate metallodendrimers such as 60 [DAB-32 = diaminobutane-dend(NH2)32].60 

Metal-promoted fusion or linkage of anionic CoC2B3 complexes affords exceedingly rich and varied chemistry. Thus, FeCl2-promoted oxidative face-to-face fusion gave Co2C4B6 clusters 62. With NiBr2, the product was a B-B 

Oxidative fusion of the ttido-, c/oro-cobaltacarborane 63, which has both C2B3 and C2B4 ligands, yielded the Ru4Co4 tetramer 64 whose structure was confirmed crystallographically.65 

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