Synthesis and characterization of rhenaannulynes†
Most reported metallacycles are limited to small cyclic complexes that contain six-membered or smaller rings. Larger-membered metallacycles are still rare and mainly focus on dimetallacycles. Herein, we report the first rhenaannulyne, a ten-membered metallacycle with a single metal center. The complex was isolated by the treatment of a silyl alkyne tethered rhenium vinyl carbyne complex with tetrabutylammonium fluoride. Its structure was identified by single-crystal X-ray diffraction and NMR studies. DFT calculation studies suggest that there is a thermodynamic origin for the conversion of the rhenavinylcarbyne complex to a rhenaannulyne. The rhenaannulyne represents a new metallacycle bearing a large ten-membered ring.