Synthesis of S‑Alkyl Phosphinocarbodithioates with Switch between P(III) and P(V) Derivatives

Simple and effective synthetic pathways are described to prepare compounds R2P­(X)­C­(S)­SCH­(Me)­Ph with the P atom either in the oxidation state V [R/X = t-Bu/O (6), Ph/S, (7), t-Bu/S (8), t-Bu/Se (9)] or III [R/X = Ph/BH3 (4), t-Bu/BH3 (5), t-Bu/lone pair (10)]. Compound 9 is the first example of carbodithioate ester with a P = Se group, and for the first time, a phosphinocarboditioate with a free phosphine function (compound 10) is described. Stabilization of the latter crucially depends on the steric protection by the t-Bu groups since an analogous derivative with R = Ph is observable but too unstable for isolation. Compound 10 can be reversibly protonated to yield the [t-Bu2PHC­(S)­SCH­(Me)­Ph]+ cation (10-H+), which was isolated as a BF4– salt. A few interconversion processes resulting in the facile addition/removal or exchange of the X group in this family of compounds are also described. The oxidation state of the phosphorus atom and the nature of an electron-withdrawing group have a significant impact on the spectral properties.