Rational design of ruthenium complexes: P,Arene-Chelation and Anion effects in bond activation and catalysis

This dissertation explores the rational design of ruthenium complexes with a focus on how ligand architecture and anion identity affect bond activation and catalytic performance. Two complementary strategies are developed: stabilization of low-valent Ru(0) species through P,arene-chelation, and modulation of Ru(II)-catalyzed asymmetric hydrogenation via sulfonate anions.Ruthenium(0) complexes exhibit exceptional potential for atom-economical transformations and inert bond activation, yet their practical use is severely limited by the intrinsic conflict between high reactivity and poor stability, particularly in phosphine-based systems prone to cyclometalation. In Chapter 2, a novel carbonyl-free phosphine-based Ru(0) complex, Ru(BINAP)(PPh₃), is designed and synthesized via dehydrohalogenation. Structural characterization reveals a unique P,arene-chelation mode in which one phosphine donor and a naphthalene moiety from the BINAP ligand simultaneously coordinate to the Ru(0) center. This hemilabile coordination confers remarkable thermal stability while preserving high reactivity. The complex behaves as a “masked” 16-electron species, readily undergoing ligand exchange with alkenes and dienes, and enabling the activation of C–H, N–H, and even inert C–N bonds under mild conditions. These findings demonstrate a viable strategy to reconcile stability and reactivity in phosphine-based Ru(0) chemistry.In Chapter 3, the P,arene-chelation concept is extended to biaryl monophosphine ligands, including MOP and Buchwald-type ligands. A practical one-pot synthetic route to Ru(0) complexes from [Ru(p-cymene)Cl₂]₂ using Zn/LiCl as a mild reductant is developed. Comparative studies reveal how subtle differences in ligand topology and electronic properties dramatically influence coordination behavior and bond activation pathways, offering new insights into the structure–reactivity relationships of low-valent ruthenium complexes.Beyond neutral ligand design, this work also addresses the often-overlooked role of anionic ligands in catalysis. Chapter 4 systematically investigates sulfonate anions (OMs⁻, OTs⁻, and OTf⁻) in Ru(II)-BINAP-catalyzed asymmetric hydrogenation. A facile one-pot synthesis of Ru(diphosphine)-bis-sulfonate complexes is established. These catalysts exhibit enhanced activity and robustness compared to conventional acetate analogues, underscoring the critical influence of weakly coordinating, highly labile anions on catalytic performance.Collectively, this dissertation demonstrates that both coordinating and anionic ligands can be deliberately engineered to control the delicate balance between stability, reactivity, and selectivity in ruthenium catalysis. The concepts developed herein provide new design principles for low-valent and cationic ruthenium complexes, contributing to the broader goal of advancing practical, efficient, and sustainable transition-metal catalysis.