Synthesis and characterization of phosphorous(III) diisocyanate and triisocyanate.

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 (nP), low-temperature single-crystal X-ray diffraction (XRD) of solid ClP(NCO)2 reveals a Cs symmetric syn-configuration for both NCO ligands with weak CO (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 nP, leading to a propeller-shaped structure with slightly distorted C3v symmetry due to steric repulsion of the NCO ligands and the PO vdW interactions (r = 3.1901(1) Å) in the solid state.