Synthesis of N- and B-Substituted Derivatives of closo-Amino-undecahydro-dodecaborate(1-) Anion

Abstract

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)2NH-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 11B, 1H NMR and negative FAB mass spectrometry methods.