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Abstract

From the analysis of pK_a values of eight mercaptodicarba-closo-dodecaboranes (1-o, 8-o, 9-o, 1-m, 4-m, 9-m, 1-p, 2-p) and pK_a' values of five of their -SCH₂COOH derivatives was stated: 1) icosahedral skeleton is capable of conjugative interactions with HS- and generally with all groups of +M character, 2) the measure of M interaction with HS is practically the same in all positions and is very similar to that in benzenethiol, 3) pK_a value of HS-isomer reflects the magnitude of the group charge ε on BH or CH according to equation pK_a = 7.43-26.5ε; ε values lie between -0.10 (9-o) and +0.156 (1-o) and correlate well with dipole moment and chemical reactivity.