THE REACTION OF ELECTROPHILIC TERMINAL PHOSPHINIDENE COMPLEXES WITH BENZOPHENONE AND FLUORENONE - THE UNEXPECTED FORMATION OF 6-MEMBERED AND 8-MEMBERED HETEROCYCLES

The phenylphosphinidene-pentacarbonyltungsten complex 2, as generated from the appropriate 7-phosphanorbornadiene complex 1, reacts at 60 de grees C with benzophenone to give a benzo-annellated 1-oxa-2-phosphacy clohex-4-ene 2-oxide as a 1:1 mixture of two isomers 3a,b. The same ph osphinidene complex 2 reacts at 120 degrees C with fluorenone. A deoxy genation of fluorenone takes place leading to the bifluorenylidene 4 a nd to an eight-membered 1,2,8-oxadiphosphocane 2,8-dioxide 5. Both com pounds 3b and 8 have been fully characterized by X-ray crystal structu re analysis. The two reactions are interpreted as resulting from the i nitial formation of a P ... O Lewis adduct between the phosphinidene a nd the ketone.