W. Dean Harman, James F. Wishart, and Henry Taube Inorg. Chem. 28, 2411-2413 (1989)
Abstract:
When Os(NH3)5(CF3SO3)3 is reduced in the presence of diphenylacetylene, four pentaammineosmium complexes can be isolated and characterized in which the alkyne remains intact. The kinetically favored mononuclear complex features a phenyl group (eta)2-bound to the metal center. This species is observed to undergo a linkage isomerization in which the osmium migrates to the alkyne. Through the use of pulse radiolysis, this isomerization was determined to be greatly accelerated by oxidizing the metal to Os(III). The inherent stability of alkyne complexes for both di- and trivalent osmium species provides the opportunity to assess the ability of this ligand to act as a pi-donor as well as a pi-acceptor.