Hydroselenation and Carboselenation of Electron‐Deficient Alkynes with Isolable (Hydrido)(selenolato)platinum(II) Complexes and a Selenaplatinacycle Bearing a Triptycene Skeleton

The reaction of [PtH(SeTrip)(PPh 3 ) 2 ] (Trip = 9‐triptycyl) ( 3 ) with dimethyl acetylenedicarboxylate (DMAD) or methyl propiolate gave hydroselenation syn adducts. The reaction of [PtH(SeTrip)(dppe)] [dppe = 1,2‐bis(diphenylphosphanyl)ethane], which has a stronger phosphane σ‐donor ligand than 3 , with DMAD gave both syn and anti adducts. The reaction of 3 and DMAD in the presence of PPh 3 yielded no adducts. These observations indicate that, in the hydroselenation, the dissociation of a PPh 3 ligand from 3 is a key step. The selenaplatinacycle 6 , which is a thermal reaction product of 3 , reacted with DMAD to give the carboselenation product, 1 H ‐2‐benzoselenin 7 , which was also formed by the reaction of TripSeH with DMAD.