This review summarizes data on the main types of charge-compensated nido-carborane derivatives. Compared with organic analogs, onium derivatives of nido-carborane have increased stability due to the stabilizing electron-donor action of the boron cage. Charge-compensated derivatives are considered according to the type of heteroatom bonded to a boron atom.

The crystal structure of 1,12-diiodo-ortho-carborane 1,12-I₂-1,2-C₂B₁₀H₁₀ was determined by single crystal X-ray diffraction. In contrary to earlier studied 1,12-dibromo analogue 1,12-Br₂-1,2- C₂B₁₀H₁₀, its crystal packing is governed by the presence of the intermolecular I⋯I dihalogen bonds between the iodine atom attached to the carbon atom (acceptor) and the iodine atom attached to the antipodal boron atom (donor) of the carborane cage. The observed dihalogen bonds belong to the II type and are characterized by classical parameters: shortened I⋯I distance of 3.5687(9) Å, C–I⋯I angle of 172.61(11)° and B–I⋯I angle of 92.98(12)°.

The 1,4-dioxane derivative of cobalt bis(dicarbollide) reacts with dialkylsulfides and triphenylphosphine to give the corresponding sulfonium and phosphonium derivatives [8-L(CH₂CH₂O)₂-3,3′-Co(1,2-C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)] (L = SMe₂, S(CH₂CH₂)₂O, PPh₃). The treatment of the triphenylphosphonium derivative with sodium hydroxide results in contraction of the side chain with formation of [8-HOCH₂CH₂O-3,3′-Co(1,2-C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)]⁻. The same product was obtained by treatment of the dimethylsulfonium derivative with the poorly nucleophilic base t-BuOK, whereas the stronger nucleophiles induce the sulfur demethylation to give [8-MeS(CH₂CH₂O)₂-3,3′-Co(1,2-C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)]⁻. The alcohol was used for the synthesis of a series of other short-spacer functional derivatives [8-XOCH₂CH₂O-3,3′-Co(1,2-C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)]⁻ (X = NH₂, SH, N₃). A similar contraction of the disclosed 1,4-dioxane ring via the reactions with SMe₂ and PPh₃ can be used for the synthesis of short-spacer functional derivatives of nido-carborane, whereas the 1,4-dioxane derivatives of closo-decaborate and closo-dodecaborate anions, being stronger electron donors, are more stable and do not react with dimethylsulfide and triphenylphosphine.

The crystal structures of two isomeric triiodo derivatives of ortho-carborane containing substituents in the three most electron-withdrawing positions of the carborane cage, 1,2,3-I₃-1,2-C₂B₁₀H₉, and the three most electron-donating positions, 8,9,12-I₃-1,2-C₂B₁₀H₉, as well as the crystal structure of 8,9,12-Br₃-1,2-C₂B₁₀H₉, were determined by single-crystal X-ray diffraction. In the structure of 1,2,3-I₃-1,2-C₂B₁₀H₉, an iodine atom attached to the boron atom (position 3) donates its lone pairs simultaneously to the σ-holes of both iodine atoms attached to the carbon atoms (positions 1 and 2) with the I⋯I distance of 3.554(2) Å and the C-I⋯I and B-I⋯I angles of 169.2(2)° and 92.2(2)°, respectively. The structure is additionally stabilized by a few B-H⋯I-shortened contacts. In the structure of 8,9,12-I₃-1,2-C₂B₁₀H₉, the I⋯I contacts of type II are very weak (the I⋯I distance is 4.268(4) Å, the B8-I8⋯I12 and B12-I12⋯I8 angles are 130.2(3)° and 92.2(3)°) and can only be regarded as dihalogen bonds formally. In comparison with the latter, the structure of 8,9,12-Br₃-1,2-C₂B₁₀H₉ demonstrates both similarities and differences. No Br⋯Br contacts of type II are observed, while there are two Br⋯Br halogen bonds of type I.