690258-90-3Relevant academic research and scientific papers
Cleavage of Conjugated Alkenes by Cationic Osmium Nitrides: Scope of the Reaction and Dynamics of the Azaallenium Products
Maestri, Aaron G.,Taylor, Scheroi D.,Schuck, Stephany M.,Brown, Seth N.
, p. 1932 - 1946 (2008/10/09)
The cationic osmium(VI) nitride complex cis-[(terpy)OsNCl 2]PF6 (1; terpy = 2,2′6′,2″-terpyridine) reacts with a variety of aryl-substituted alkenes and acyclic and cyclic dienes to form the η2-azaallenium complexes cis-[(terpy)OsCl 2(RR′C=N=CHR″)]PF6 (2) by net nitrogen atom insertion into a C=C double bond. More electron-rich alkenes are more reactive, and electron-poor alkenes such as cinnamate esters do not react. Isomeric trans-[(terpy)OsNCl2]PF6 (3), as well as the tris(pyrazolyl)methane complex [(Tpm)OsNCl2]PF6 (4), give analogous products, although the scope of the reaction is restricted to dienes with these nitrides. The aryl-substituted azaallenium complexes cis-[(terpy)OsCl2(η2(C,N)-R[Ar]C=N=CHR″)]PF 6 display hindered rotation about the C-Cipso bond, because π-stacking interactions favor a close approach of the aryl group to the terpyridine ligand. The osmium migrates slowly between the two C=N bonds of the azaallenium ligands, leading to both regio- and stereoisomerizations. These two processes can be observed separately in the case of cis-[(terpy)OsCl 2([p-Me2NC6H4]CH=N=CHCH 3)]PF6, with regioisomerization preceding stereoisomerization. The isomerizations appear to take place by an allene-roll mechanism, as judged by the similar rates observed for cyclic and acyclic azaallenium complexes.
