Forging Three Single Bonds on One Carbon via Metal Carbynes or Carbyne Equivalents

Metal carbyne(M≡C)complexes have been discovered for nearly half a century,however,they gained far less study in comparison with metal-carbon single bond(M—C)and metal carbene(M=C)species in synthetic chemistry.Up to three sigma bonds are possibly forged on a single carbon through metal carbynes or carbyne equivalents,which holds great potentials in organic synthesis but also requires high efficiency of bond formation and precise control of reactivity and selectivity.Along this line,two systems based on stoi-chiometric transformations of manganese carbynes and ruthenium/rhodium-catalyzed reactions of diazo hypervalent iodine reagents,carbyne equivalents,have emerged recently,which will be highlighted herein.Future potentials and challenges in this intriguing area are also briefly discussed.