Hydrogen-Bonded π Complexes between Phosphaethyne and Hydrogen Chloride.

Area of Science:

• Inorganic Chemistry
• Physical Chemistry
• Computational Chemistry

Background:

• Phosphaethyne (HCP) is a highly reactive and unstable molecule.
• Understanding the interactions of HCP with small molecules like HCl is crucial for exploring novel chemical bonding.
• Matrix isolation techniques allow for the study of transient species at low temperatures.

Purpose of the Study:

• To synthesize and characterize novel 1:1 and 1:2 complexes of phosphaethyne (HCP) and hydrogen chloride (HCl).
• To elucidate the structural preferences and isomeric diversity of these labile complexes.
• To investigate the nature of bonding in HCP-HCl complexes using spectroscopic and computational methods.

Main Methods:

• Laser photolysis of molecular precursors (1-chlorophosphaethene and dichloromethylphosphine) in argon and nitrogen matrices at 10 K.
• Infrared (IR) spectroscopy for structural identification.
• Deuterium (D)-isotope labeling studies.
• High-level quantum chemical calculations (CCSD(T)-F12a/cc-pVTZ-F12).

Main Results:

• Successful generation of highly labile 1:1 and 1:2 HCP-HCl complexes.
• Identification of a preferred T-shaped structure for the 1:1 complex, with HCl as the hydrogen donor to the C≡P triple bond.
• Observation of three distinct isomeric structures for the 1:2 complex, all based on the T-shaped 1:1 core.
• Spectroscopic data and computational results corroborate the proposed structures.

Conclusions:

• The study provides the first detailed structural characterization of rare HCP π-electron complexes with HCl.
• The findings highlight the versatility of HCP in forming complexes with varying stoichiometries and isomeric forms.
• This work advances the understanding of non-covalent interactions involving unsaturated phosphorus compounds.