2‐(Trimethylsilyl)‐λ 3 ‐Phosphinine: Synthesis, Coordination Chemistry, and Reactivity

The [4+2] cycloaddition reaction between 2‐pyrone and Me 3 Si−C≡P gives the corresponding 2‐(trimethylsilyl)‐λ 3 ‐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 C 5 H 5 P by means of protodesilylation with HCl. C 5 H 5 P reacts with CuBr⋅S(CH 3 ) 2 to give an infinite Cu(I)Br coordination polymer. DFT calculations shed light on the influence of the ‐Si(CH 3 ) 3 group on the electronic properties of the aromatic phosphorus heterocycle.