Figure 2.

A) Synthesis of 3 and 4 from 2: a) 5 equiv. Se, CDCl₃, 5 d, 25 °C; b) 1 equiv. B(C₆F₅)₃, C₆D₆, 16 h, 25 °C; Molecular structure of 3 (B) and 4 (C) in the solid state (thermal ellipsoids set at the 50 % probability level); hydrogen atoms omitted for clarity. Selected bond lengths [Å] and angles [°]: 3 P1–N1 1.667(2), P1–N2 1.700(2), P1–S1 2.1263(10), P1–Se1 2.0643(7); N1‐P1‐N2 93.05(12), N1‐P1‐S1 115.74(9), N2‐P1‐S1 95.59(9); 4 P1–N1 1.6793(16), P1–N2 1.7126(15), P1–S1 2.1181(6), P1–B1 2.0823(19); N1‐P1‐N2 93.80(8), N1‐P1‐S1 116.62(6), N2‐P1‐S1 93.35(5). ^[9]