Synthesis and structure of 1,12-diethynyl-para-carborane

Base desilylation of the novel compound, 1,12-bis(trimethylsilylethynyl)-para-carborane 1,12-(Me3SiCC)2-1,12-C2B10H10, gave the previously unknown compound 1,12-bis(diethynyl)-para-carborane, 1,12-(HCC)2-1,12-C2B10H10. In the structure of the latter carborane, determined by X-ray diffraction, the ethynyl substituents induce a distortion of the carborane icosahedron, lengthening the tropical BB bonds. The structural parameters of the diethynyl carborane are compared with known structures of type 1,12-(XE)2B10H10 bearing substituents on antipodal sites particularly the isostructural and isoelectronic 1,12-B12H10(CO)2.