Mercury derivatives of polyhedral boranes, carboranes, and metallacarboranes

Synthesis and Reactivity of Cyclic Oxonium Derivatives of nido-Carborane: A Review

“…It is assumed that the selectivity of the reactions in these cases is determined by the fact that the endo-polyhedral hydrogen atom of nido-carborane cage is replaced at the first stage of the reaction by a mercury atom with the formation of η 1 -metallacarborane, in which mercury is bound to the B(10) atom of the dicarbollide ligand [64][65][66][67]. Heating of this complex results in elimination of mercury and generation of quasi-electrophilic center at position 10 followed by its attack by the nucleophile [60].…”

Effect of Nature of Substituents on Coordination Properties of Mono- and Disubstituted Derivatives of Boron Cluster Anions [BnHn]2– (n = 10, 12) and Carboranes with exo-Polyhedral B–X Bonds (X = N, O, S, Hal)

“…The boron atoms in carboranes have a lower negative charge as compared to boron clusters; therefore, their ability to act as a donor of electronic density reduces. In this case, there are the following ways to form complexes with carboranes: (i) the formation of a B-Hg bond during electrophilic mercurization, which proceeds to the position furthest from the carbon atoms (actually, formation of a C-Hg bond is also possible) (see review [57] and references thereof); (ii) B-H activation with the formation of a B-M bond in the presence of a substituent with a donor atom in the ortho position acting as a ligand (the substituent is usually attached to the carbon atom); therefore, activation of neighboring positions is observed (see reviews [58,59] and recent articles [60,61]); (iii) coordination by a substituent, as a rule, attached to the carbon atom of carborane cage (see, for example, review [62]).…”