Experimental and theoretical study of phosphinine sulfides

Abstract

The first examples of phosphinine sulfides (3 and 4) were prepared by sulfuration of the corresponding phosphinines (1 and 2). These new compounds have been fully characterised by NMR spectroscopy and X-ray diffraction analysis. The precise electronic structure of the parent phosphinine oxide (III) and sulfide (IV) was investigated at the DFT level and compared to the parent phosphinine (I) and 1-methylphosphininium cation (II). According to this computational study, the phosphinine sulfide and oxide are aromatic compounds. In the phosphinine sulfide the sulfur lone pairs are efficiently stabilized by two σ*(P–C) orbitals and the phosphinine π* system. Oxidation of the phosphinine leads to a complete reorganisation of the P hybridization state. The variations observed across the series follow Bent’s rule and are in excellent agreement with the experimental data.