The First OCCCO Pentadentate Chelates: Osmium Mediated Stepwise Oxidations of Terminal Alkynes by Pyridine N-Oxide

The Summary of main observation and conclusion Oxygen atom transfer reactions between alkynes and heteroareneN-oxides are currently mediated by transition metal, such as gold, ruthenium or rhodium, but they have never been catalyzed by osmium. Herein, we report stepwise oxidations of terminal alkynes mediated by an osmium carbolong complex, using pyridineN-oxide as the oxidant, yielding novel aldehyde- or carboxylic acid-coordinated osmapentalyne derivatives selectively. The mechanism was illustrated by density functional theory calculations, providing a new route for oxygen atom transfer between heteroareneN-oxides and alkynes.