Synthesis and characterization of phosphorous(iii) diisocyanate and triisocyanate

Abstract

Two phosphorous(III) isocyanates, ClP(NCO)₂ and P(NCO)₃ were isolated as neat substances and characterized with IR (gas-phase and Ne-matrix), Raman (solid), and ³¹P NMR spectroscopy. Their vibrational spectra were analyzed in terms of a single conformer with the aid of quantum chemical computations at the B3LYP/6-311+G(3df) level of theory. In line with the theoretically computed favorable syn-configuration of the NCO ligands with the sterically active lone-pair electrons on the central phosphorous atom (n_P), low-temperature single-crystal X-ray diffraction (XRD) of solid ClP(NCO)₂ reveals a C_s symmetric syn-configuration for both NCO ligands with weak C⋯O (r = 2.9692(4) Å) van der Waals (vdW) interactions. In the binary isocyante P(NCO)₃, all the three NCO ligands adopt similar syn-configuration with n_P, leading to a propeller-shaped structure with slightly distorted C_3v symmetry due to steric repulsion of the NCO ligands and the P⋯O vdW interactions (r = 3.1901(1) Å) in the solid state.