Direct synthesis of nido-carborane derivatives with pendant functional groups by copper-promoted reactions with dimethylalkylamines

A series of novel neutral nido-carboranes [9-Z(CH2)nMe2N-nido-7,8-C2B9H11] with various pendant functional groups (n = 1, Z = Ph, Ctriple bond; length of mdashN, Ctriple bond; length of mdashCH; n = 2, Z = OH, NMe2; n = 3, Z = OH, Cl) was synthesized by copper(II) promoted reactions of the parent nido-carborane with the corresponding dimethylalkylamines. In solution compound [9-HO(CH2)3Me2N-nido-7,8-C2B9H11] undergoes cyclization to give the unusual product [κO-4,κN-9-(μ-O(CH2)3Me2N)-nido-7,8-C2B9H10] which features a seven-member exo-polyhedral ring. The water-soluble positively charged derivatives with terminal allyl and propargyl groups [9-RCH2Me2N(CH2)nMe2N-nido-7,8-C2B9H11]+ (R = CHdouble bond; length as m-dashCH2, Ctriple bond; length of mdashCH) were prepared by the alkylation of [9-Me2N(CH2)2Me2N-nido-7,8-C2B9H11]. The crystal structures of [9-ZCH2Me2N-nido-7,8-C2B9H11] (Z = Ph, CH2Ctriple bond; length of mdashN, CH2Ctriple bond; length of mdashCH) and cyclic [κO-4,κN-9-(μ-O(CH2)3Me2N)-nido-7,8-C2B9H10] were determined by single-crystal X-ray analysis.