Synthesis and Rearrangement of P-Nitroxyl-Substituted P^IIIand P^VPhosphanes: A Combined Experimental and Theoretical Case Study

Low-temperature generation of P-nitroxyl phosphane 2 (Ph₂POTEMP), which was obtained by the reaction of Ph₂PH (1) with two equivalents of TEMPO, is presented. Upon warming, phosphane 2 decomposed to give P-nitroxyl phosphane P-oxide 3 (Ph₂P(O)OTEMP) as one of the final products. This facile synthetic protocol also enabled access to P-sulfide and P-borane derivatives 7 and 13, respectively, by using Ph₂P(S)H (6) or Ph₂P(BH₃)H (11) and TEMPO. Phosphane sulfide 7 revealed a rearrangement to phosphane oxide 8 (Ph₂P(O)STEMP) in CDCl₃at ambient temperature, whereas in THF, thermal decomposition of sulfide 7 yielded salt 10 ([TEMP-H₂][Ph₂P(S)O]). As well as EPR and detailed NMR kinetic studies, indepth theoretical studies provided an insight into the reaction pathways and spin-density distributions of the reactive intermediates.