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 beta-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 approximately 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 beta-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.