Aspects of phosphaallene chemistry – heat induced formation of 1,2-dihydrophosphetes by intramolecular nucleophilic aromatic substitution and photochemical generation of tricyclic phosphiranes

3H-Phosphaallenes are accessible on a new and facile route and show a fascinating chemical behavior. The thermally in-duced rearrangement of Mes*-P=C=C(H)R’ (R’ = tBu, Ad) afforded by C-H activation, isobutene elimination, C-C and P-H bond formation bicyclic 1-benzo-dihydrophosphetes (2) with PC3 heterocycles. DFT calculations suggest a mechanism with intramolecular nucleophilic aromatic substitution and replacement of an alkyl group by the nucleophilic α-C atom of the phosphaallene. These bicycles formed W(CO)5 complexes (3) or yielded by catalyst-free hydrophosphination of alkynes 1,2-dihydrophosphetes with P bound alkenyl groups (4 and 5). The resulting bulky phosphines formed complexes with IrCp*Cl2, RuCl2, AuCl or CuO3SCF3. The Ru atom is coordinated by the P atom and a phenyl group. Irradiation of Trip-P=C=C(H)tBu led by the insertion of the central C atom of the P=C=C group into the α-C-H bond of an iPr substituent and by C-C and P-C bond formation to a new isomer of phosphaallenes, 10, which featu...