Redox Non‐Innocence and Isomer‐Specific Oxidative Functionalization of Ruthenium‐Coordinated β‐Ketoiminate

This article deals with isomeric ruthenium complexes [Ru III (L R ) 2 (acac)] ( S= 1/2) involving unsymmetric β‐ketoiminates (AcNac) (L R =R‐AcNac, R=H ( 1 ), Cl ( 2 ), OMe ( 3 ); acac=acetylacetonate) [R= para ‐substituents (H, Cl, OMe) of N ‐bearing aryl group]. The isomeric identities of the complexes, cct ( cis ‐ cis‐trans , blue, a ), ctc ( cis‐trans‐cis, green, b ) and ccc ( cis ‐ cis‐cis , pink, c ) with respect to oxygen (acac), oxygen (L) and nitrogen (L) donors, respectively, were authenticated by their single‐crystal X‐ray structures and spectroscopic/electrochemical features. One‐electron reversible oxidation and reduction processes of 1 – 3 led to the electronic formulations of [Ru III (L)(L ⋅ )(acac)] + and [Ru II (L) 2 (acac)] − for 1 + ‐ 3 + ( S= 1) and 1 − – 3 − ( S= 0), respectively. The triplet state of 1 + ‐ 3 + was corroborated by its forbidden weak half‐field signal near g ≈4.0 at 4 K, revealing the non‐innocent feature of L. Interestingly, among the three isomeric forms ( a – c in 1 – 3 ), the ctc ( b in 2 b or 3 b ) isomer selectively underwent oxidative functionalization at the central β‐carbon (C−H→C=O) of one of the L ligands in air, leading to the formation of diamagnetic [Ru II (L)(L ′ )(acac)] (L ′ =diketoimine) in 4 / 4′ . Mechanistic aspects of the oxygenation process of AcNac in 2 b were also explored via kinetic and theoretical studies.