A Journey from 12-Vertex to 14-Vertex Carboranes and to 15-Vertex Metallacarboranes

Abstract

Icosahedral o-carboranes are readily reduced by group 1 metals to give "carbon atoms apart" (CAp) nido-carborane dianions that can be further reduced to the corresponding arachno-carborane tetraanions with the assistance of transition-metal ions. The geometries of the arachno species are dependent upon the electronic configurations of transition-metal ions. In contrast, "carbon atoms adjacent" (CAd) nidocarborane dianions can react with lithium metal, in the absence of any transition-metal ions, to produce CAd arachno-carborane tetraanions having a significantly different structure from their CAp counterparts. These CAd nido-and arachno-carborane anions possess a reducing power weaker than that of the CAp isomers, which can facilitate the capitation reactions of these anions with boron dihalides. This important discovery provides a very valuable entry point to the synthesis of 13-and 14-vertex carboranes. Subsequently, the largest heteroborane, 15-vertex metallacarborane, has been prepared. These studies open up new possibilities for the development of polyhedral clusters of extraordinary size. This review offers an overview of recent advances in this growing research field.

Direct insertion of sulfur, selenium and tellurium atoms into metallaborane cages using chalcogen powders

“…Although the structural diversity of polyhedral metallaborane chemistry is in theory also accessible to any combinations of main-group elements that have the same numbers of valence electrons, this chemistry is dominated by carboranes [1][2][3][4][5][6] and metallacarboranes [7][8][9][10][11][12][13][14]. Apart from the carboranes and metallacarboranes, the most wide-ranging maingroup polyhedral heteroboranes are thiaboranes and thiametallaboranes.…”

Polyphenylsilsesquioxanes. New structures–new properties

“…84 To some extent, this operation makes them related to another class of unique organoelement polycycles, namely, carboranes. [85][86][87][88] Moreover, two faces can be opened by increasing the amount of the alkali (Fig. 13).…”

On Desilylation of 13‐Vertex Carborane 1,2‐Me2Si(CH2)2‐1,2‐C2B11H11

“…Reduction of 2 with an excess amount of Na metal in THF at room temperature, followed by treatment with 0. 5 (6b) as a beige crystalline solid in 20% isolated yield, respectively (Scheme 1). It is not uncommon that structural rearrangements proceed during capitation process.…”

“…Only in recent years has significant progress been made in the chemistry of supercarboranes. [5] A number of 13-and 14-vertex carboranes have been prepared and structurally characterized. [6][7][8][9][10][11][12][13][14] Such a breakthrough relied on the use of CAd (Carbon-Atoms-Adjacent) nido-carborane dianions or arachno-carborane tetraanions as starting materials.…”