The reaction of a selenoxide 2 of 1,11-(methanoxomethano)-5H,7H-dibenzo[b,g][1,5]-diselenocine 1 with triflic anhydride gives a new selenurane dication salt 3 with two unsymmetrical apical oxy- and seleno-ligands, i.e. the chair form of 2 is changed to the boat form of 3 by the three centre transannular interaction between the oxygen and the two selenium atoms.
