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 [R 2 NH-B 12 H 11 ] - derivatives (R = C 6 H 5 CH 2 , 2-C 10 H 7 CH 2 , n -C 16 H 33 , n -C 12 H 25 ) were obtained via conventional alkylation of 1 in aqueous propan-2-ol, starting from bulky primary alkylhalides. These [R 2 NH-B 12 H 11 ] - 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-CH 2 ) 2 NH-B 12 H 11 ] - 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-B 12 H 11 ] - , 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-BrMgC 10 H 7 . All derivatives were characterized by high-field 11 B, 1 H NMR and negative FAB mass spectrometry methods.