Chiral Cobalt‐Salen Complexes: Ubiquitous Species in Asymmetric Catalysis

Abstract

Since the discovery of their extraordinary reactivity in the hydrolytic kinetic resolution of terminal epoxides about twenty years ago, chiral cobalt‐salen complexes have been shown to be essential for many other asymmetric catalytic reactions. This account summarizes the inspiring works dedicated to the discovery of their new reactivity and their mode of action, as well as the new processes towards the optimization of their cooperativity for bimetallic activation and the implementation of their effective immobilization, including also our contribution on these topics.

Molecular and Electronic Structures of a Series of Dinuclear CoII Complexes Varied by Exogeneous Ligands: Influence of π‐Bonding on Redox Potentials

“…Cobalt complexes gained renewed interest due to their diverse functional properties in metalloenzymes, [1][2][3][4] as single-molecule magnets, [5][6][7][8][9][10][11][12][13][14][15][16] in catalysis, [17][18][19][20][21] water oxidation, [22][23][24][25][26][27] proton reduction, [22,[28][29][30][31][32][33][34][35][36][37][38] carbon dioxide reduction, [28,[39][40][41][42][43][44] and cytotoxicity. [45] In order to mimic dinuclear metalloenzymes active sites and consequently to obtain new dinuclear catalysts we have recently developed a dinucleating ligand system comprised of two tetradentate tripodally coordinating ligand compartments with varying terminal donors that are bridged by an ethylene spacer.…”

Ferrocene functionalized enantiomerically pure Schiff bases and their Zn(ii) and Pd(ii) complexes: a spectroscopic, crystallographic, electrochemical and computational investigation

“…[23][24][25] Schiff bases, characterized by an imine (4CQN-) or an azomethine (-CHQN-) group, 26,27 form an outstanding class of proligands that play a key role in the development of coordination chemistry due to their facile synthesis, structural flexibility, easily tunable electronic properties, selectivity and sensitivity towards the coordinated metal ion and their ability to form stable complexes under various coordination geometries and oxidation states. 22,[28][29][30] Transition-metal complexes of Schiff base ligands have been widely investigated because of their applications in various branches of science such as in catalysis, [31][32][33] sensing, [34][35][36] as NLO molecular materials, 23,[37][38][39] and in biochemistry, [40][41][42] among others. Ferrocene substituted asymmetric N 2 O 2 -tetradentate Schiff bases are generally obtained upon condensation of salicylaldehyde or its derivatives with a preformed tridentate organometallic precursor bearing a free amino group.…”

Theoretical Studies on Bimetallic Salen Complexes Catalyzed Epoxide Hydration: Effects of Metal Centers, Substrates, and Ligands

“…In the past few decades, catalytic hydration of epoxides has been investigated to obtain environmentally friendly glycol at a low energy cost, and various types of catalysts, such as ionic liquids, ,, zeolites, − and metal–salen catalysts, − have been explored. Metal–salen complexes are versatile and have been proven to be effective catalysts for epoxide hydration, apart from asymmetric ring-opening reactions, CO 2 cycloaddition/copolymerization with epoxides, and asymmetric alkene epoxidation/Diels–Alder reactions. − …”