Characterizing the B-P stretching vibration in phosphorus-substituted phosphine boranes

Area of Science:

• * Inorganic Chemistry
• * Computational Chemistry
• * Spectroscopy

Background:

• * Phosphine boranes are compounds featuring a boron-phosphorus bond.
• * Understanding their vibrational properties is crucial for characterizing their structure and bonding.
• * Previous studies have explored various phosphorus-containing molecules, but detailed analysis of substituted phosphine boranes is ongoing.

Purpose of the Study:

• * To present and analyze experimental Raman spectra of three novel phosphorus-substituted phosphine boranes.
• * To compare experimental results with theoretical calculations using electronic structure methods.
• * To investigate the vibrational mixing of the boron-phosphorus (B-P) dative bond.

Main Methods:

• * Experimental Raman spectroscopy was employed to obtain spectra of crystalline phosphine boranes.
• * Electronic structure computations were performed using the M06-2X method with the 6-311G(2df, 2pd) basis set.
• * Total-energy distributions (TEDs) were calculated to analyze vibrational modes.

Main Results:

• * The chosen computational level accurately reproduced the experimental B-P stretching frequencies for all studied phosphine boranes.
• * Calculations revealed the degree of mixing between the B-P stretching vibration and other internal coordinates.
• * Simulated Raman spectra for smaller B-P containing molecules, including phosphine borane (BH(3)PH(3)), matched existing experimental data.

Conclusions:

• * The M06-2X/6-311G(2df, 2pd) level of theory is a reliable tool for predicting B-P stretching frequencies in phosphine boranes.
• * Vibrational analysis using TEDs provides insight into the nature of the B-P dative bond.
• * The study validates computational methods for the characterization of these important inorganic compounds.