Synthesis and Catalytic Performance of a Novel Ruthenium (II) PNN Pincer Complex Containing a Bipyridine Ring in Olefin Oxidation

ABSTRACT

A novel ruthenium (II) PNN pincer complex (Ru‐1) containing a bipyridine ring was designed and synthesized in this study, and its performance as a homogeneous catalyst in olefin oxidation reactions was systematically investigated. Raw materials were prepared via Schlenk technique, and ligand L ₁ as well as the target complex Ru‐1 were synthesized through multi‐step reactions. The structure of Ru‐1 was characterized by ¹ H NMR, ³¹ P NMR, high‐resolution mass spectrometry (HR‐MS), and X‐ray crystallography, which confirmed the configuration of Ru‐1. Catalytic performance studies showed that Ru‐1 exhibited excellent catalytic activity and stability in styrene oxidation: when the catalyst dosage was as low as 1.00 × 10 ⁻⁷  mol%, 100% conversion could still be achieved, with a turnover number (TON) exceeding 1.0 × 10 ⁹ and a maximum turnover frequency (TOF) reaching 5.0 × 10 ⁷  h ⁻¹ . Using H ₅ IO ₆ as the oxidant and ethyl acetate/water (1:1) as the mixed solvent, the selectivity for benzaldehyde was up to 99.0% at room temperature, which effectively suppressed side reactions. In addition, this catalyst had broad substrate compatibility and could efficiently catalyze the oxidation of styrene derivatives, internal olefins, alkynes, and natural products with a styrene structure, generating the corresponding aldehydes and ketones, respectively. This study provides an efficient and green catalytic system for the selective oxidation of olefins, highlighting the application value of bipyridine‐based PNN ligands in the field of organometallic catalysis.