Phosphorus-Boron Multiple Bonding in the π Radical HBP

Area of Science:

• Inorganic Chemistry
• Quantum Chemistry
• Spectroscopy

Background:

• Understanding the electronic structure and bonding of novel small molecules is crucial in chemistry.
• Boron-phosphorus compounds are of interest due to their unique bonding characteristics and potential applications.
• Previous studies on isovalent species like HNB provide a basis for comparison.

Purpose of the Study:

• To synthesize and characterize the hydrogen boron phosphide (HBP) radical.
• To elucidate the electronic ground state and bonding nature of HBP.
• To compare the bonding properties of HBP with its isovalent analog, HNB.

Main Methods:

• Generation of the HBP radical using laser ablation of boron atoms reacting with phosphine (PH3) in a solid neon matrix.
• Identification and characterization via infrared (IR) spectroscopy with isotopic substitutions.
• Validation of experimental findings through quantum chemical calculations.

Main Results:

• The HBP radical was successfully generated and identified.
• HBP exhibits a 2Π electronic ground state with a short boron-phosphorus bond.
• Bonding analysis reveals a σ bond and two degenerate π bonding orbitals with three electrons, resulting in a bond order of 2.5 between P and B.

Conclusions:

• The HBP radical possesses a unique bonding configuration with a bond order of two and a half.
• This bonding characteristic is significantly different from the isovalent HNB radical, which has a triple bond.
• The study provides fundamental insights into the electronic structure and chemical bonding of boron-phosphorus compounds.