Practical synthesis of 9-methylthio-7,8-nido-carborane [9-MeS-7,8-C2B9H11]-. Some evidences of BH•••X hydride-halogen bonds in 9-XCH2(Me)S-7,8-C2B9H11 (X = Cl, Br, I)

Convenient method of synthesis of 9-methylthio-7,8-nido-carborane [9-MeS-7,8-C2B9H11](-) based on demethylation of the dimethylsulfonium derivative 9-Me2S-7,8-C2B9H11 with sodium amide in toluene was developed. A series of alkylmethylsulfonium derivatives of nido-carborane containing heteroatoms with lone electron pairs at alpha-position of alkyl were prepared 9-XCH2(Me)S-7,8-C2B9H11 (X = Cl, Br, I, OMe) by alkylation of [9-MeS-7,8-C2B9H11](-). The B-11 NMR spectra of these compounds demonstrate splitting signals corresponding to B(5) and B(10) atoms that can be explained by the weak intramolecular B-H center dot center dot center dot X interactions in the diastereomers containing alkyl groups directed downwards and upwards relatively to the nido-carborane pentagonal face. The existence of such interactions was supported by quantum chemical calculations. (C) 2017 Elsevier B.V. All rights reserved.