Muonated radicals formed from phenyl- and silyl-substituted acetylenes

Implantation of positive muons into samples of PhCCPh and PhCCMe at 298 K led to the formation of the radicals PhĊC(Mu)Ph and PhĊC(Mu)Me; in the case of the latter compound, the alternative MeĊC(Mu)Ph radical was not detected. Additionally, cyclohexadienyl radicals formed by muonium atom addition to the aromatic rings were observed, in lower yield, allowing spin-delocalisation parameters (Δx) to be determined for the –CCR substituents. During irradiation of Me3SiCCMe, the Me3SiĊC(Mu)Me radical was observed.