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

Abstract

The reaction of 4,5-dimethyl-2-phenylphosphinine with sulfur in boiling benzene in the presence of Nmethylimiduzole 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 I ,2,4-thiadiphospholane heterocy- cle. The P-C bridge is weak [1.881(3) A] and sulfur can insert into it to give the symmetrical tetrasulfide with two P-S-C bridges.According to a preliminary study [ 11, the reaction of phosphinines with sulfur initially yields very reactive phosphinine 1-sulfides in which the . In view of the aromaticity loss that accompanies the sulfuration of phosphorus, it seemed to us that the reaction of phosphinines with sulfur deserved more attention. We therefore decided to investigate in more depth the reaction of 4,S-dimethyl-2-phenylphosphinine (1) with sulfur.In our initial report, phosphinine 1 (a3'P + 185) was allowed to react with sulfur in boiling xylene.A signal at 6 + 145.7 appeared on the 3 i P NMR spectrum of the crude reaction mixture which was assigned to the phosphinine sulfide 2 on the basis of trapping reactions with 2,3-dimethylbutadiene and dimethyl acetylenedicarboxylate (Eq. 1). Me ' s;%CO2Me S C02Mei,