Pentavalent P…π phosphorus bonding with associated Cl…π halogen bonding in influencing the geometry of POCl3-Phenylacetylene heterodimers: Evidence from matrix isolation infrared spectroscopy and ab initio computations

Abstract

Of the two diverse oxidation states, phosphorus exists in its pentavalent state in a majority of real-life systems. In the present study, the role of Cl…π halogen bonding with co-operative pentavalent P…π phosphorus bonding in influencing the geometry of POCl3-PhAc heterodimers has been experimentally proved at low temperatures. The experiments were performed by co-deposition of POCl3 and PhAc under matrix isolated conditions followed by infrared spectral characterization. The structural elucidation of all possible 1:1 POCl3-PhAc heterodimers was accomplished using ab initio and DFT computational methodologies. Of the four minima revealed by computations performed at MP2 level of theory using aug-cc-pVDZ basis set, the energetically favoured minimum generated experimentally was stabilized dominantly by Cl…π halogen bonding interactions. However, the associated primary role of P…π phosphorus bonding in determining the geometry of this dimer has been firmly established, with reinforcements from Electrostatic Potential Mapping, Natural Bond Orbital, Energy Decomposition and Non-Covalent Interaction analyses.