Persulfuration of phosphinines: Synthesis and X-ray crystal structure analysis of a P2S3 derivative

The reaction of 4,5-dimethyl-2-phenylphosphinine with sulfur in boiling benzene in the presence of N-methylimidazole as a catalyst first yields a P-sulfide. This monosulfide further reacts with sulfur to give a diphosphinine trisulfide and a diphosphinine tetrasulfide. The X-ray crystal structure analysis of the trisulfide has been carried out. The two head-to-tail 1,6-dihydrophosphinine rings are connected by P S C and P C links, thus forming a central 1,2,4-thiadiphospholane heterocycle. The P C bridge is weak [1.881(3) Å] and sulfur can insert into it to give the symmetrical tetrasulfide with two P S C bridges.