New synthetic and structural studies on nitroso-ortho-carboranes RCB10H10CNO and bis(ortho-carboranyl)amines (RCB10H10C)2NH (R=Ph or Me)

Abstract: Improved procedures are reported for the preparation of nitroso-carboranes RCb°NO (Cb°=1,2-C2B10H10; R=Ph, Me at cage carbon C2) in 44–77% yield, and of dicarboranylamines (RCb°)2NH in 55–65% yield by reactions between the lithio-carboranes, RCb°Li and nitrosyl chloride, NOCl, in cold mixtures of diethyl ether and either pentane (for RCb°NO) or dimethoxyethane (for (RCb°)2NH). Deprotonation of the amines by KOtBu in toluene in the presence of 18-crown-6, (CH2CH2O)6, affords the salts [K(18-crown-6)]+[(RCb°)2N]−. X-ray crystal structures of PhCb°NO, (PhCb°)2NH, (MeCb°)2NH and [K(18-crown-6)]+[(PhCb°)2N]− are described, and the bonding implications of their cage C…C distances (1.68, 1.80, 1.75 and 1.99Å, respectively) are discussed. These species provide further striking examples of the remarkable capacity of the ortho-carborane cage to act as a sensitive indicator of the π-donor characteristics of ligands attached to its cage carbon atoms. [Copyright &y& Elsevier]