Reactivity of a Bis(alkynyl)-Vinylidene Osmium Complex: Access to Carbynes, Vinyl Ester Derivatives, and C–C and C–N Bond-Forming Reactions

Subsequent protonation of <b>2</b> with HOTf or Et₃N·3HF affords the bis(alkynyl)-carbyne derivatives [Os(C≡C^tBu)₂(≡CCH₂^tBu)(PⁱPr₃)₂]OTf (<b>3</b>) and OsF(C≡C^tBu)₂(≡CCH₂^tBu)(PⁱPr₃)₂ (<b>4</b>), respectively.

In contrast, treatment of <b>2</b> with acetic acid leads to the alkynyl-vinylidene-vinyl ester derivative Os(C≡C^tBu){κ²-<i>O,C</i>-OC(CH₃)OC=CH^tBu}(=C=CH^tBu)(PⁱPr₃)₂ (<b>5</b>). Density functional theory (DFT) calculations, together with deuterium labeling experiments, demonstrate that the protonation may occur either at the C_β carbon of the vinylidene ligand or at the C_β carbon atom of one of the alkynyl groups, and that the formation of <b>5</b> is governed by thermodynamic control.