ESR SPECTROSCOPIC CHARACTERIZATION OF A COORDINATED ALKYNE RADICAL, AND REDOX-INDUCED VINYLIDENE ALKYNE COMPLEX ISOMERIZATION

One-electron oxidation of [Cr(CO)2(RC2R)(eta-C6Me6)] 1 gives paramagnetic [Cr(CO)2(RC2R)(eta-C6Me6)]+ 1+ in which the unpaired electron is highly delocalised onto the alkyne; the radical cation (1+; R = SiMe3) is an intermediate in the oxidative isomerisation of the vinylidene complex [Cr(CO)2{C=C(SiMe3)2}(eta-C6Me6)] 2 to [Cr(CO)2(Me3SiC2SiMe3)(eta-C6Me6)] (1; R = SiMe3).