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

Abstract

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. Abinitio 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.