Syntheses of the novel cage compounds P3Se3C3But3 and P3Se4C3But3 and an unusual insertion reaction of [PtCl2(PMe3)] into the Se-Se bond of the latterto give the six-coordinate Pt(IV) complex [PtCl2(PMe3)P3Se4C3But3]

The novel cage compounds P3Se3C3But3 and P3Se4C3But3 are formed (together with the 1,2,4-selenadiphosphole P2SeC2But2) from the reaction of the phosphaalkyne ButCP with selenium; the [PtCl2(PMe3)] fragment undergoes an unusual insertion reaction into the Se–Se bond of P3Se4C3- But3.