Osmium-Centered Oxetylidene: Formation and Cleavage

The first transition-metal-oxetylidene complex has been prepared by reaction of OsCl(η5-C5H5)(CO)(P iPr3) with 3,3-di(methoxycarbonyl)-5-hexyn-1-al and AgBF4. This novel compound is transformed into a hydroxyalkenylcarbene isomer by deprotonation and subsequent protonation of the resulting α,β-unsaturated acyl transient species. In fluorobenzene at 90 C, the four-membered ring undergoes cycloreversion to afford a cis-dicarbonyl derivative and the cycloalkene. © 2012 American Chemical Society.Financial support from the MINECO of Spain (proyect number CTQ2011-23459) and Consolider Ingenio 2010 (CSD2007- 00006), The Diputación General de Aragón (E35), and the European Social Fund are acknowledged. M.B. thanks the Spanish MEC for a predoctoral grant.Peer Reviewe