Synthesis of N- and B-substituted derivatives of closo-amino-undecahydro-dodecaborate(1-) anion

The synthesis of nitrogen and boron substituted derivatives of the 1-amino-closo-dodecaborate anion(1-) 1 is reported. Reasonable yields of the [R2NH-B12H11](-) derivatives (R = C6H5CH2, 2-C10H7CH2, n-C16H33, n-C12H25) were obtained via conventional alkylation of 1 in aqueous propan-2-ol, starting from bulky primary alkylhalides. These [R2NH-B12H11](-) derivatives were subsequently methylated by dimethyl sulfate under similar conditions. Reaction of 1 with palmitoyl chloride gave under anhydrous conditions the corresponding N-acyl derivative. Reaction of 1 with hydroxymethyl-18-crown-6 tosylate in THF in the presence of NaH led to the novel [(18-crown-6-CH2)(2)NH-B12H11](-) anion, the Cs+ salt of which exhibits unusual solubility properties. A direct cyclization reaction of pentaethylene glycol ditosylate with 1 gave under similar conditions [(15-azacrown)-5-B12H11](-), the first known closo-borate anion with an attached aza-crown ring. These species exhibit potentially interesting complexation efficiency and solubility properties. Selective substitution of the boron cage by a bulky naphthyl substituent was achieved by palladium-mediated cross-coupling reaction between 1 and 1-BrMgC10H7. All derivatives were characterized by high-field B-11, H-1 NMR and negative FAB mass spectrometry methods.