N–H···O=P hydrogen-bonded dimers as the main structural motif of aminophosphonate diesters

Crystal and molecular structures of three aminophosphonate diesters, diethyl and dibutyl (a-(quinolin- 3-ylamino)-N-benzyl)phosphonates (1 and 2) and dibutyl (a-anilino-(quinolin-3-yl)methyl)phosphonate (3) were reported and comparatively discussed. Characteristic struc- tural features for these compounds are strong N-H��� O=P hydrogen bonds that connect two organophosphorus mol- ecules in cyclic centrosymmetric dimer. Phosphoryl oxy- gen forms additional interaction with a C-H donor from the nearby aromatic group. Dimer formation in solution was also confirmed using electrospray ionization mass spectrometry. Mass spectra of six structurally similar aminophosphonate derivatives, 1-3 along with diethyl (a-anilino-(quinolin-3-yl)methyl)phosphonate (4), diethyl and dibutyl (a-anilino-(quinolin-2-yl)methyl)phosphonates (5 and 6) were studied and dimolecular ions (2M ? Na) ? and (2M ? H) ? were observed.