CYCLIC NIOBIC(V) AND TANTALIC(V) ACID ESTERS

NbCl5 and TaCl5 react in benzene with 2,3-dihydroxynaphthalene, 1,8-dihydroxynaphthalene and 2,2′-dihydroxybiphenylresp. 2,2′-dihydroxybinaphthyl by substitution of chlorine atoms giving hexacoordinated five-, six- and seven-membered rings of types H[M(2,3-C10H6O2)3], H[M(1,8-C10H6O2)3] and H[M(C12H8O2)3] resp. H[M(C20H12O2)3] (M=Nb, Ta). By reaction with amines, NH3 and lithiumbutyl the corresponding ammonium- and lithium salts are obtained. All compounds have been characterised by analytical data, i.r. absorption spectra and polarographic examination. © 1969.