SYNTHESIS AND CHARACTERIZATION OF CYANOHYDROISOCYANOBORATES - REACTIVITY OF THE ISOCYANO GROUP TOWARDS NUCLEOPHILES

AgCNBH2CN and AgCNBH(CN)(2) were synthesized with AgCN in Me2S from Me 2S . BH2CN and 4-cyanopyridine . BH(CN)(2), respectively. These silver complexes were transformed Into Na[BH2(CN)NC] and Na[BH(CN)(2)NC] sal ts. In these hydrolytically very stable borates the isocyano group pro ved to be the most reactive site. This observation was demonstrated by reactions with nucleophiles, namely H2S, NH4N3 and NH4SCN. In the fir st two cases isocyano group underwent transformation into -N(H)-C(H)=S and -1-(5H)tetrazolyl groups, respectively, which remarkably increase the stability of hydroborates towards acidic hydrolysis. Unlike alkyl - or arylisocyanides, isocyano groups here do not form ring in reactio n with NH4CN, but most probably transform into -N = C(H)- NCS groups. All compounds, including the E- and Z-isomers (where appropriate), wer e characterized by IR, H-1, B-11 and C-13 NMR spectroscopy. (C) 1998 E lsevier Science Ltd. Ail rights reserved.