Formation of van der Waals complexes between allene and HCl in cryosolutions.: An IR and ab initio study

The mid-IR spectra of mixtures of allene (C3H4) and hydrogen chloride, dissolved in liquid argon (LAr) and in liquid nitrogen (LN2), have been investigated between 98 and 120 K. They show that a 1 : 1 complex C3H4 . HCl and a 1 : 2 complex C3H4 . (HCl)(2) are formed in LAr, while only the 1 : 1 complex was detected in LN2. The complexation enthalpies for the 1 : 1 complex were determined to be - 6.4(3) kJ mol(-1) (LAr) and -5.1(4) kJ mol(-1) (LN2), while for the 1 : 2 complex a value of -14.6(6) kJ mol(-1) (LAr) was derived. Ab initio calculations, at the MP2/6-31 + G(d,p) level, of structures and IR spectra of monomers and complexes were made. Comparison with the experimental spectra shows that the 1 : 2 complex has a chain structure, in which the second HCl molecule is bonded to the chlorine atom of the first.