Redox-Promoted Linkage Isomerizations of Aldehydes and Ketones on Pentaammineosmium

Article abstract of DOI:10.1021/ja00216a016

Upon one-electron reduction, 1-(CH3)2CO)>³⁺ undergoes an η¹->η² isomerization at a specific rate of 6*10³ s^-1.Through the investigation of the homogeneous oxidation of 2-(CH3)2CO)>²⁺, a specific rate of 1.3 s^-1 for the η²->η¹ isomerization has also been determined.Thus, η²-coordination is preferred by 5.0 kcal mol^-1 for acetone bound to pentaammineosmium(II).The investigation has been extended to other aldehydes and ketones in order to explore of the effects of strain, conjugation, and steric hindrance in the η⁵-bound ligand.Pentaammineosmium(II) was also found to interact with the aromatic portion of the phenones investigated.In these complexes, the metal coordinates η² to the arene, interrupting its aromaticity.Upon oxidation, an intramolecular isomerization occurs in which the Os(III) species adopt an η¹-coordination at the carbonyl.