Issue 23, 2019

Elusive hypervalent phosphorus⋯π interactions: evidence for paradigm transformation from hydrogen to phosphorus bonding at low temperatures

Abstract

The π electron systems are the conventional electron donors to the hydrogen acceptors in hydrogen bonding. Apart from the hydrogen atom, halogens, chalcogens, pnicogens and triel/tetrel atoms can also be envisaged as electron acceptors involving π clouds. Markedly, in pnicogen⋯π interactions, the bonding of the hypervalent (predominantly pentavalent) state of the phosphorus atom with π electron donors is elusive and can be thought of as an intuitive extension to trivalent phosphorus⋯π interactions. In this work, on the one hand, POCl3 was taken as a prototypical molecule to explore these pentavalent phosphorus interactions and on the other hand, acetylene (C2H2), ethylene (C2H4) and benzene (C6H6), in which phosphorus⋯π bonding can be expected to compete with hydrogen and halogen bonding interactions, were taken as π electron donors. All three POCl3–C2H2, POCl3–C2H4 and POCl3–C6H6 heterodimers were experimentally generated at low temperatures in Ar and N2 matrices and were characterized by both infrared spectroscopy and state-of-the-art quantum chemical computations. Though hydrogen bonding dominates in POCl3–C2H2 and POCl3–C2H4 heterodimers, phosphorus bonding plays a definite and non-trivial role in their overall stabilization. An interesting paradigm transformation was noticed in the POCl3–C6H6 system, where pentavalent phosphorus⋯π bonding was observed to completely influence the hydrogen bonding interaction. To further shed light on these P⋯π systems, the interaction characteristics were analyzed with the help of electrostatic potential mapping, natural bond orbital and energy decomposition analyses.

Graphical abstract: Elusive hypervalent phosphorus⋯π interactions: evidence for paradigm transformation from hydrogen to phosphorus bonding at low temperatures

Supplementary files

Article information

Article type
Paper
Submitted
06 Apr 2019
Accepted
14 May 2019
First published
14 May 2019

Phys. Chem. Chem. Phys., 2019,21, 12250-12264

Elusive hypervalent phosphorus⋯π interactions: evidence for paradigm transformation from hydrogen to phosphorus bonding at low temperatures

P. K. Sruthi, S. Sarkar, N. Ramanathan and K. Sundararajan, Phys. Chem. Chem. Phys., 2019, 21, 12250 DOI: 10.1039/C9CP01925A

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