2-(Trimethylsilyl)-λ³-Phosphinine: Synthesis, Coordination Chemistry, and Reactivity

The [4+2] cycloaddition reaction between 2-pyrone and Me₃Si−C≡P gives the corresponding 2-(trimethylsilyl)-λ³-phosphinine in good yields as a rather air and moisture stable, colorless oil. Insight into the regioselectivity of the pericyclic reaction was obtained with the help of deuterium-labeling experiments. The silyl-phosphinine acts as a ligand for the preparation of a Cu(I) and the first crystallographically characterized phosphinine-Ag(I) complex. The title compound was further used as a starting material for an alternative preparation of the parent phosphinine C₅H₅P by means of protodesilylation with HCl. C₅H₅P reacts with CuBr⋅S(CH₃)₂ to give an infinite Cu(I)Br coordination polymer. DFT calculations shed light on the influence of the -Si(CH₃)₃ group on the electronic properties of the aromatic phosphorus heterocycle.