Reversible Complexation of Alkynes by a Germylene

Abstract

The diarylgermylene Ge(ArMe6)2 (ArMe6 = C6H3-2,6-(C6H2-2,4,6-Me3)2) is shown to react reversibly with the four unstrained alkynes 3-hexyne, diphenylacetylene, trimethylsilylacetylene, and phenylacetylene at ambient temperature in toluene. The germirene products (ArMe6)2GeC(R)═C(R′) (R, R′ = Et, Et (1a), Ph, Ph (1b), H, SiMe3 (1c), H, Ph (1d) were characterized by 1H and 13C NMR spectroscopy and by X-ray crystallography in the case of 1a and 1d. The thermodynamic parameters of the reactions were determined by variable-temperature 1H NMR spectroscopy, and the experimental Gibbs free energies indicated their near-thermoneutrality and relatively weak alkyne coordination.