Formation of phosphanoxy-substituted phosphaalkenes via sterically promoted cleavage of the P=P diphosphene bond

Gold(I) Complexation of Phosphanoxy-Substituted Phosphaalkenes for Activation-Free LAuCl Catalysis

The phosphanoxy-substituted phosphaalkene bearing the P=C-O-P skeleton can be prepared from diphosphene Mes*P=PMes* (Mes*=2,4,6-tBu₃ C₆ H₂ ), and their use for catalysis is of interest. In this paper, complexation of the phosphanoxy-substituted phosphaalkenes with gold are investigated, and the catalytic activity of the mono- and bis(chlorogold) complexes are subsequently evaluated. Reaction of the P=C-O-P compound with (tht)AuCl (tht=tetrahydrothiophene) showed dominant coordination on the sp³ phosphorus, and complete coordination on the sp² phosphorus required removal of tetrahydrothiophene. Atoms In Molecules (AIM) analysis based on the X-ray structure of the mono(chlorogold) complex indicated a pseudo coordinating interaction between the gold center and the P=C unit. The bis(chlorogold) complexes displayed conformational isomerism, and catalyzed the cycloisomerization/alkoxycyclization of 1,6-enyne and for hydration of terminal alkyne without activation treatment. Even the mono(chlorogold) complexes catalyzed the alkoxycyclization reactions without a silver co-catalyst, indicating that the alcohols were effective in activating the AuCl unit.

Free Radical Reactivity of a Phosphaalkene Explored Through Studies of Radical Isotopologues

Muonium (Mu), an H atom analogue, is employed to probe the addition of free radicals to the P=C bond of a phosphaalkene. Specifically, two unprecedented muoniated free radicals, MesP^. -CMu(Me)₂ (1 a, minor product) and MesPMu-C^. Me₂ (1 b, major product), were detected by muon spin spectroscopy (μSR) when a solution of MesP=CMe₂ (1: Mes=2,4,6-trimethylphenyl) was exposed to a beam of positive muons (μ⁺ ). The μ⁺ serves as a source of Mu (that is, Mu=μ⁺ +e^- ). To confirm the identity of the major product 1 b, its spectral features were compared to its isotopologue, MesPH-C^. (Me)CH₂ Mu (2 a). Conveniently, 2 a is the sole product of the reaction of MesPH(CMe=CH₂ ) (2) with Mu. For all observed radicals, muon, proton, and phosphorus hyperfine coupling constants were determined by μSR and compared to DFT-calculated values.