Low-frequency vibrational spectra of some 4-benzylpiperidinium and N-benzylpiperazinium pentahalogenoantimonates(III) and pentahalogenobismuthates(III). Partial crystal structure determination of 4-benzylpiperidinium pentachloroantimonate(III)

Abstract

Some compounds of the type [bzpipn]₂[MX₅] and [bzpipzn][MX₅](bzpipn = 4-benzylpiperidinium cation; bzpipzn =N-benzylpiperazinium dication; M = Sb or Bi; X = Cl or Br) have been prepared and characterized by means of Raman and far-i.r. spectroscopy. The crystal data, although poor, of the [bzpipn]₂[SbCl₅] compound show that the antimony atom is surrounded by six chlorine atoms. Five of these are strictly bonded to the metal atom (2.5 Å), forming a square-pyramidal SbCl₅^2– unit, and another chlorine atom of an adjacent SbCl₅^2– unit completes the octahedral co-ordination around the metal atom through a weak interaction (3.2 Å), giving rise to infinite chains running along the c axis. The molecular structures of the complexes depend more on the halogen atoms than on the counter-cation dimensions and hydrogen-bonding abilities. In fact the vibrational spectra of all the chloro-anions may be interpreted on the basis of the crystal structure of the [bzpipn]₂[SbCl₅] compound, while those of the bromo-anions suggest the presence of a distorted octahedron of bromine atoms around the metal with two bromine bridges that link adjacent metal atoms.