A focused review on the unconventional alkyne activations by ruthenium(II) and osmium(II) complexes supported by 1,2-bis(diphenylphosphino)methane (dppm)

While the activation of alkynes by ruthenium(II) and osmium(II) bis-diphosphine complexes in the form of [Ru^II/Os^II(P^P)₂X₂] has been studied for nearly three decades and are known to give a variety of metal−vinylidene, −allenylidene, and −alkynyl complexes, recent findings on the isolation of unprecedented organometallic complexes from alkynes and [Ru^II/Os^II(P^P)₂X₂] suggest the existence of unconventional reaction pathways which have been largely overlooked. In this focused review, a brief overview on the conventional reactivities between alkynes and cis-[Ru^II/Os^II(dppm)₂Cl₂] (dppm = 1,2-bis(diphenylphosphino)methane) will first be provided, which is then followed by discussions on the recent discoveries of the unconventional reactivities with emphasis on the mechanistic insights into the Ru/Os-induced alkyne transformations.