Dipole Moments, Nuclear Quadrupole Coupling, and the Bonding Orbitals in Group V—Trihalides

Abstract

By means of microwave spectral measurements the following molecular parameters have been determined: 1. The dipole moment of NF₃ is 0.235±0.007 Debye. 2. The nuclear quadrupole coupling of arsenic in AsCl₃ is —173±20 Mc. 3. The internuclear distance Sb–Cl and the bond angle Cl–Sb–Cl are 2.325±0.005A and 99.5±1.5°, respectively, in SbCl₃. The measured molecular parameters of the group V‐trihalides are assembled and interpreted in terms of s—p hybridization, partial ionic, and partial multiple bond character. In particular, certain regularities in the dipole moments are pointed out which indicate that apparent anomalies in the dipole moments of these molecules can be understood in terms of s—p hybridization. From the evidence of nuclear hyperfine structure, it appears that NF₃ and AsH₃, as was previously suggested for NH₃, have an s—p hybridization which is not simply related to the bond angles. The quadrupole coupling per p‐electron of N¹⁴, previously reported to have been established by the measurements on NF₃, has been again thrown open to question.