A Low‐Spin Ruthenium(IV)–Oxo Complex: Does the Spin State Have an Impact on the Reactivity?

Abstract

High-valent metal-oxo complexes are key reactive species for oxidation and oxygenation of organic compounds in nature as well as in the laboratory. [1, 2] Although iron is the most common metal species among high-valent metal-oxo complexes, [3] there are also manganese-oxo, [4] ruthenium-oxo, [5] and other metal-oxo complexes.[6] High-valent metal-oxo species are produced by reductive activation of molecular oxygen coupled with proton transfer. [7][8][9] Peroxides such as hydrogen peroxide can provide a so-called "peroxide shunt" to produce high-valent metal-oxo species.[1-3] High-valent metal-oxo species can also be produced by proton-coupled electron transfer (PCET), in which deprotonation of a coordinated water molecule and oxidation of the metal center occur concertedly. [10][11][12][13][14] The reactivity of high-valent metal-oxo species varies depending on the type of metal, the oxidation state of the metal center, ligands, and the spin state. Theoretical studies proposed that the reactivity of high-valent metal-oxo species may be determined by two closely lying spin states, which have different activation barriers for the reactions with substrates. [15][16][17] The most straightforward way to clarify the effects of spin states on the reactivity of highvalent metal-oxo species is to examine the reactivity of an analogous series of metal-oxo complexes that have different spin states. There have been extensive studies on Ru IV

Synthesis, Structural Characterization and Antimicrobial Evaluation of Ruthenium Complexes with Heteroaromatic Carboxylic Acids

“…The existence of the chelatoaromaticity phenomenon can influence the stability of the complex, which is crucial for its application in medicinal chemistry . A similar N,O‐coordination mode was found in trans ‐[Ru(2,3‐pydcH) 2 (PPh 3 ) 2 ] and [Ru(6‐COO − ‐tpa)Cl]ClO 4 . The ruthenium ion also coordinates with two chloride anions to give a RuN 2 O 2 Cl 2 chromophore.…”

“…To the best of our knowledge, no previous study on the antibiofilm activity of ruthenium(III) and (IV) complexes against P. aeruginosa has been reported. Importantly, among the high‐valent ruthenium complexes generally complexes with oxo, nitrido and porphyrin ligands are known and used as catalysts in organic synthesis …”

A Two‐in‐one Pincer Ligand and its Diiron(II) Complex Showing Spin State Switching in Solution through Reversible Ligand Exchange

“…One may speculate about potential sensor applications of such bi-and multistable systems, but we find the prospect of tuning chemical reactivity (e.g., the reaction of diferrous complexes with O 2 ) by temperature-induced spin state changes in solution, such as observed here, a particularly interesting perspective. [24] More generally, in view of the rapidly developing catalytic applications of mononuclear pincer complexes (with a recent emphasis on iron pincer complexes), [13,25] we anticipate exciting chemistry of bimetallic systems with two potentially synergetic pincer-type subunits based on L À or related ligands. .…”

Do spin state and spin density affect hydrogen atom transfer reactivity?

“…10 Singlet metal complexes including d 0 permanganate and chromium(VI) compounds have also been shown, in studies starting in the 1960s, to abstract H • from hydrocarbon substrates. 11,12 A number of recent reports describe H-atom abstractions by a variety of d n metal species (n > 0) with singlet ground states, including Goldberg’s Mn V (O), 13 Kojima’s 7-coordinate Ru IV (O), 14 and Tolman’s Cu III (OH) 15 complexes. 16 …”