Formation of the elusive tetrahedral P<sub>3</sub>N molecule.

Zhang, Chaojiang; Zhu, Cheng; Eckhardt, André K; Kaiser, Ralf I · Sci Adv · 2022

basic_science · Level V

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Abstract

The tetrahedral 1,2,3-triphospha-4-azatricyclo [1.1.0.0<sup>2,4</sup>] butane (P<sub>3</sub>N) molecule-an isovalent species of phosphorus (P<sub>4</sub>)-was prepared in low-temperature (5 K) phosphine-nitrogen ices and was identified in the gas phase through isomer-selective, tunable, soft photoionization reflectron time-of-flight mass spectrometry. Theoretical calculations reveal that the substitution of a single phosphorus atom by nitrogen in the P<sub>4</sub> molecule results in enhanced spherical aromaticity while simultaneously increasing the strain energy from 74 to 195 kJ mol<sup>-1</sup>. In P<sub>3</sub>N, the P─P bond is shortened compared to those in P<sub>4</sub> by 3.6 pm, while the P─N─P bond angle of 73.0° is larger by 13.0° compared to the P─P─P bond angle of 60.0° in P<sub>4</sub>. The identification of tetrahedral P<sub>3</sub>N enhances our fundamental understanding of the chemical bonding, electronic structure, and stability of binary, interpnictide tetrahedral molecules and reveals a universal route to prepare ring strained cage molecules in extreme environments.