Alkyne oligomerization mediated by rhodium complexes with a phosphinosulfonamido ligand and isolation and characterization of a rhodacyclopentadiene complex

Treatment of N-tosyl aziridine with KPPh2 in THF produces Ph2PCH2CH2NTsK (Ts = p-CH3C6H4SO2). Reaction of Ph2PCH2CH2NTsK with [Rh2(μ2-Cl)2(NBD)2] (NBD = norbornadiene) and [Rh2(μ2-Cl)2(COD)2] (COD = 1,5-cyclooctadiene) produces [Rh(NBD)(Ph2PCH2CH2NTs)] and [Rh(COD)(Ph2PCH2CH2NTs)] (4), respectively. Reaction of Ph2PCH2CH2NTsK with [Ir2(μ2-Cl)2(COD)2] gives [Ir(COD)(Ph2PCH2CH2NTs)]. Complex 4 is catalytically active for polymerization of arylalkynes and for cyclotrimerization of HCtriple bond; length of mdashCCOR (R = OEt, Me). The novel metallacycle [Rh(C(CO2Et)double bond; length as m-dashCHC(CO2Et)double bond; length as m-dashCH)(CH(CO2Et)double bond; length as m-dashCCtriple bond; length of mdashCCO2Et)(Ph2PCH2CH2NHTs)2] was isolated from the reaction of 4 with ethyl propiolate. The metallacycle is catalytically active for cyclotrimerization of ethyl propiolate.