Evidence for Phosphorus Bonding in Phosphorus Trichloride–Methanol Adduct: A Matrix Isolation Infrared and ab Initio Computational Study

Abstract

The weak interaction between PCl3 and CH3OH was investigated using matrix isolation infrared spectroscopy and ab initio computations. In a nitrogen matrix at low temperature, the noncovalent adduct was generated and characterized using Fourier transform infrared spectroscopy. Computations were performed at B3LYP/6-311++G(d,p), B3LYP/aug-cc-pVDZ, and MP2/6-311++G(d,p) levels of theory to optimize the possible geometries of PCl3-CH3OH adducts. Computations revealed two minima on the potential energy surface, of which, the global minimum is stabilized by a noncovalent P···O interaction, known as a pnictogen bonding (phosphorus bonding or P-bonding). The local minimum corresponded to a cyclic adduct, stabilized by the conventional hydrogen bonding (Cl···H-O and Cl···H-C interactions). Experimentally, 1:1 P-bonded PCl3-CH3OH adduct in nitrogen matrix was identified, where shifts in the P-Cl modes of PCl3, O-C, and O-H modes of CH3OH submolecules were observed. The observed vibrational frequencies of the P-bonded adduct in a nitrogen matrix agreed well with the computed frequencies. Furthermore, computations also predicted that the P-bonded adduct is stronger than H-bonded adduct by ∼1.56 kcal/mol. Atoms in molecules and natural bond orbital analyses were performed to understand the nature of interactions and effect of charge transfer interaction on the stability of the adducts.

Matrix isolation FTIR study of hydrogen-bonded complexes of methanol with heterocyclic organic compounds

“…Gas phase reaction of phosphorus trichloride (PCl 3 ) and MeOH was carried out at different ratios of PCl 3 /MeOH and the products were identied using matrix isolation infrared spectroscopy. 21 Infrared vibrational spectra of matrix isolated PCl 3 , MeOH and their complexes were analyzed and assigned by comparing the observed and calculated frequencies and intensities. The experimental evidence for the noncovalent P/O interaction in PCl 3 -MeOH adducts was provided.…”

Gas phase reaction of phosphorus trichloride and methanol: Matrix isolation infrared and DFT studies

“…Importantly, these new features are not due to the PCl 3 eCH 3 OH adducts in the N 2 matrix, as the adduct features were characterized in the earlier study [25].…”

“…The lone pair of electrons on oxygen of CH 3 OH attacks the electrophilic phosphorus of PCl 3 with a simultaneous cleavage of one of the PeCl bonds and the product DCMP is formed as shown in Fig. 2 3 OH were co-deposited through twin-jet nozzle in a N 2 matrix instead of premixing the gases and then deposited [25]. Recently, extensive [39e43] and named it as pnictogen bonding or more specifically phosphorus bonding.…”

“…1a, grid A). Multiple features observed in the n 3 (e) mode in N 2 matrix has already been assigned to i) isotopic effect of chlorine ( 35 Cl: 37 Cl ¼ 3:0/2:1/1:2), ii) splitting of degenerate vibrational states due to the host matrix atoms and iii) matrix site effect or unification of two or more of these effects [25].…”

Features of the Pnictogen Bonds Formed by Neighboring Nitro Groups in Crystals

“…The B…P bond length was significantly lower than the sum of the van der Waals radii, and the energy value exceeded 10 kcal/mol. In study [24] the presence of a non-covalent O…P bond in the CH 3 -HO…PCl 3 adducts was confirmed using infrared spectroscopy. The formation of a bound adduct was evidenced by displacements of stretching vibrations of the P-Cl, O-C, and O-H bonds into the long-wavelength region.…”