Synthesis of 9,9′,12,12′-substituted cobalt bis(dicarbollide) derivatives

A partial degradation of 9,12-disubstituted derivatives of ortho-carboranes 9,12-X-2-1,2-C2B10H10 (X = Br, Alk, Ar) led to the corresponding substituted nido-carboranes [5,6-X-2-7,8-C2B9H10](-), which on the reaction with cobalt(II) chloride gave new 9,9',12,12'-tetrasubstituted derivatives of cobalt bis(dicarbollide) [9,9',12,12'-X-4-3,3'-Co(1,2-C2B9H9)(2)](-).