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Abstract

The assymetric C₂B₇ carborane held until the present for 2,6-C₂B₇H₁₁, is in reality the arachno-4,5-C₂B₇H₁₃ carborane (I) with two adjacent B-H-B bridges, one BH₂, one CH₂ and one CH group in the hexagonal open-face. The arrangement of the boron network was determined on the basis of the ¹¹B, ¹¹B-¹¹B COSY, ¹H and ¹³C NMR spectra and on the T₁(B) study. The connection of B- with C-skeletal atoms was deduced from the positions of deuterium in the deutero analogs prepared by the CH₂O/D₃O⁺ degradation of three selectively deuterated nido-[7,8-C₂B₉H₁₂]^- anions. A selective transmission of D from CD₂O to the B(9) vertex in the course of the CD₂O/D₃O⁺ degradation was observed. The structure of arachno-4,5-C₂B₇H₁₃ is consistent with the different pathways of its preparation.