Syntheses of the novel cage compounds P3Se3C3Bu3t and P3Se4C3Bu3t and an unusual insertion reaction of [PtCl2(PMe3)] into the Se-Se bond of the latter to give the six-coordinate Pt(IV) complex [PtCl2(PMe3)P3Se4C3Bu3t]

The novel cage compounds P3Se3C3Bu3t and P3Se4C3Bu3t are formed (together w ith the 1,2,4-selenadiphosphole P2SeC2Bu2t) from the reaction of the phosph aalkyne (BuCP)-C-t with selenium; the [PtCl2(PMe3)] fragment undergoes an u nusual insertion reaction into the Se-Se bond of P3Se4C3- Bu-3(t).