Further investigations on the reactivity of rhenium arylimido-complexes and the deoxygenation reaction of RNO in [ReCl3(RNO)(OPPh3)]

Abstract

By treating [ReCl₃(NR)(PPh₃)₂](R = C₆H₄Me-p)(1) with elemental sulphur, [{ReCl₃(NR)(PPh₃)}_n](2)(n probably two) is formed, one phosphine being removed as SPPh₃. By the action of PPh₃, complex(2) can easily be converted into(1). Compound(2) proved to be more reactive than (1). The reaction with dioxygen, leading to [ReCl₃(RNO)(OPPh₃)](3), requires milder conditions when (2) is used instead of (1) and was shown to occur even with such a mild oxidant as MeC₆H₄NO₂-p. As a by-product of the reaction with dioxygen, the paramagnetic [ReCl₄(NR)(OPPh₃)](4) was formed; compound (4) is the main product when the reaction of (2) with O₂ is carried out in CCl₄. The reactions of (2) with neutral ligands such as CO, CNC₆H₁₁, OCNC₆H₁₁, and NH₂(C₆H₁₁) have been studied, the complexes [ReCl₃(NR)(PPh₃)(CO)](5), [ReCl₃(NR)(PPh₃)(CNC₆H₁₁)](6), [ReCl₃(NR)(PPh₃){NH₂(C₆H₁₁)}](7) and [{ReCl₂(NR)[NH₂(C₆H₁₁)][NH(C₆H₁₁)]}₂](8) being obtained respectively. The arylnitroso-ligand of complex (3) can be deoxygenated by reaction with tertiary phosphines PR′₂Ph (R′Ph or Et) leading to [ReCl₃(NR)(PR′₂Ph)₂] with concomitant displacement of OPPh₃ and OPR′₂Ph, or with CNC₆H₁₁ leading to [ReCl₃(NR)(CNC₆H₁₁)₂](9) and [{ReCl₃(NR)(CNC₆H₁₁)}₂O](10), the fate of CNC₆H₁₁ being unclear.