Collect. Czech. Chem. Commun. 1979, 44, 24-33

Experimental evaluation of charge distribution on particular skeletal atoms in icosahedral carboranes by means of HS-derivatives

Jaromír Plešek and Stanislav Heřmánek

Institute of Inorganic Chemistry, Czechoslovak Academy of Sciences, 250 68 Řež


From the analysis of pKa values of eight mercaptodicarba-closo-dodecaboranes (1-o, 8-o, 9-o, 1-m, 4-m, 9-m, 1-p, 2-p) and pKa' 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) pKa value of HS-isomer reflects the magnitude of the group charge ε on BH or CH according to equation pKa = 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.