摘要:
Improved procedures are reported for the preparation of nitroso-carboranes RCb degrees NO (Cb degrees = 1,2-C2B10H10; R = Ph, Me at cage carbon C2) in 44-77% yield, and of dicarboranylamines (RCb degrees)(2)NH in 55-65% yield by reactions between the lithio-carboranes, RCb degrees Li and nitrosyl chloride, NOCl, in cold mixtures of diethyl ether and either pentane (for RCb degrees NO) or dimethoxyethane (for (RCb degrees)(2)NH). Deprotonation of the amines by (KOBu)-Bu-t in toluene in the presence of 18-crown-6, (CH2CH2O)(6), affords the salts [K(18-crown-6)](+)[(RCb degrees)(2)N](-), X-ray crystal structures of PhCb degrees NO, (PhCb degrees)(2)NH, (MeCb degrees)(2)NH and [K(18-crown-6)](+)[(PhCb degrees)(2)N](-) are described, and the bonding implications of their cage C center dot center dot center dot C distances (1.68, 1.80, 1.75 and 1.99 angstrom, 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 pi-donor characteristics of ligands attached to its cage carbon atoms. (C) 2008 Elsevier Ltd. All rights reserved.