Electronic Effects on the Rates of Coupled Two-Electron/Halide Self-Exchange Reactions of Substituted Ruthenocenes

and, Timothy M. Shea; Westmoreland, T. David

doi:10.1021/ic990690b

“…This type of dynamic process has been probed by 2D EXSY techniques very infrequently. In a rare example, Westmoreland and Shea synthesised Ru complex 184 and looked at two‐electron/halide transfer self‐exchange at 25 °C (X=Cl, Br, I, Scheme ). Step‐wise methylation of the Cp ring decreases the rate of exchange monotonically, and plots of ln( k ex ) versus number of methyl groups are linear for constant X.…”

Section: Dynamic Redox Processesmentioning

confidence: 99%

“…This type of dynamic process has been probed by 2D EXSY techniques very infrequently.I narare example, [267] Westmoreland and Shea synthesised Ru complex 184 and looked at twoelectron/halide transfer self-exchange at 25 8C( X = Cl, Br,I , Scheme 60).…”

Section: Atomtransfermentioning

confidence: 99%

Mechanisms and Beyond: Elucidation of Fluxional Dynamics by Exchange NMR Spectroscopy

Nikitin

¹

,

O'Gara

²

2019

Chemistry A European J

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Detailed mechanistic information is crucial to our understanding of reaction pathways and selectivity. Dynamic exchange NMR techniques, in particular 2D exchange spectroscopy (EXSY) and its modifications, provide indispensable intricate information on the mechanisms of organic and inorganic reactions and other phenomena, for example, the dynamics of interfacial processes. In this Review, key results from exchange NMR studies of small molecules over the last few decades are systemised and discussed. After a brief introduction to the theory, the key types of dynamic processes are identified and fundamental examples given of intra‐ and intermolecular reactions, which, in turn, could involve, or not, bond‐making and bond‐breaking events. Following that logic, internal molecular rotation, intramolecular stereomutation and molecular recognition will first be considered because they do not typically involve bond breaking. Then, rearrangements, substitution‐type reactions, cyclisations, additions and other processes affecting chemical bonds will be discussed. Finally, interfacial molecular dynamics and unexpected combinations of different types of fluxional processes will also be highlighted. How exchange NMR spectroscopy helps to identify conformational changes, coordination and molecular recognition processes as well as quantify reaction energy barriers and extract detailed mechanistic information by using reaction rate theory in conjunction with computational techniques will be shown.

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Ruthenium: Organometallic ChemistryBased in part on the article Ruthenium: Organometallic Chemistry by Ulrich Koelle which appeared in the Encyclopedia of Inorganic Chemistry, First Edition .

White

¹

,

Hanusa

²

2005

Encyclopedia of Inorganic Chemistry

0

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In the slightly more than half a century that the organometallic chemistry of ruthenium has had time to develop, it has become clear that the metal's position as the ‘middle child’ of the Group 8 metals is richly reflected in its organometallic derivatives. That is, despite many similarities in the compounds of the iron–ruthenium–osmium triad, addition and elimination reactions of ruthenium, for example, are slower than those of iron but are more facile than those of osmium. Similarly, complexes with hydride and alkyl bonds are generally more stable for ruthenium than for iron, but the ruthenium compounds are often unstable or highly fluxional compared to analogous osmium species. Carbonyl cluster complexes are an important feature of organoruthenium chemistry, and mixed‐ligand carbonyl species with high nuclearity are known, in some cases with more than 10 ruthenium atoms. Interstitial carbides and nitrides are often encountered in ruthenium clusters, and carbonyl hydrides are of interest as hydroformylation catalysts (conversion of alkenes to aldehydes). The cyclopentadienyl ligand is found extensively throughout organoruthenium chemistry, and with a decomposition temperature around 600°C, the sandwich complex ruthenocene Ru(C 5 H 5 ) 2 is among the most stable organometallic compounds known. The stability of ruthenocene and its derivatives allow them to be incorporated as labels into biomolecules such as peptides. Ruthenocene derivatives have also been studied as potential second‐order nonlinear optical materials, and they have played a central role in the development of 30 valence electron triple‐decker cations of the iron group. The high ligand field stabilization of Ru II enables combinations of π‐acceptor ligands together with even the hardest σ‐donors, such as carbonate, sulfate, or nitrate, and hence Ru II carbonyl and phosphine complexes are known with myriad coligand combinations having O, N, or S binding functionalities. In particular, the ability of the (η‐arene)Ru moiety to bind N‐ and O‐ligands has been used to complex various amines, imines, Schiff bases, and amino acids to generate diastereomeric salts, which can serve as chiral catalysts; they are valuable in stereoselective organic syntheses and in the production of biologically active compounds.

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Ruthenium: Organometallic ChemistryBased in part on the article Ruthenium: Organometallic Chemistry by Ulrich Koelle which appeared in the Encyclopedia of Inorganic Chemistry, First Edition .

Quisenberry

¹

,

Hanusa

²

2005

Encyclopedia of Inorganic and Bioinorganic Chemistry

0

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In the slightly more than half a century that the organometallic chemistry of ruthenium has had time to develop, it has become clear that the metal's position as the ‘middle child’ of the Group 8 metals is richly reflected in its organometallic derivatives. That is, despite many similarities in the compounds of the iron–ruthenium–osmium triad, addition and elimination reactions of ruthenium, for example, are slower than those of iron but are more facile than those of osmium. Similarly, complexes with hydride and alkyl bonds are generally more stable for ruthenium than for iron, but the ruthenium compounds are often unstable or highly fluxional compared to analogous osmium species. Carbonyl cluster complexes are an important feature of organoruthenium chemistry, and mixed‐ligand carbonyl species with high nuclearity are known, in some cases with more than 10 ruthenium atoms. Interstitial carbides and nitrides are often encountered in ruthenium clusters, and carbonyl hydrides are of interest as hydroformylation catalysts (conversion of alkenes to aldehydes). The cyclopentadienyl ligand is found extensively throughout organoruthenium chemistry, and with a decomposition temperature around 600°C, the sandwich complex ruthenocene Ru(C 5 H 5 ) 2 is among the most stable organometallic compounds known. The stability of ruthenocene and its derivatives allow them to be incorporated as labels into biomolecules such as peptides. Ruthenocene derivatives have also been studied as potential second‐order nonlinear optical materials, and they have played a central role in the development of 30 valence electron triple‐decker cations of the iron group. The high ligand field stabilization of Ru II enables combinations of π‐acceptor ligands together with even the hardest σ‐donors, such as carbonate, sulfate, or nitrate, and hence Ru II carbonyl and phosphine complexes are known with myriad coligand combinations having O, N, or S binding functionalities. In particular, the ability of the (η‐arene)Ru moiety to bind N‐ and O‐ligands has been used to complex various amines, imines, Schiff bases, and amino acids to generate diastereomeric salts, which can serve as chiral catalysts; they are valuable in stereoselective organic syntheses and in the production of biologically active compounds.

show abstract

Electronic Effects on the Rates of Coupled Two-Electron/Halide Self-Exchange Reactions of Substituted Ruthenocenes

Cited by 5 publications

References 26 publications

Mechanisms and Beyond: Elucidation of Fluxional Dynamics by Exchange NMR Spectroscopy

Mechanisms and Beyond: Elucidation of Fluxional Dynamics by Exchange NMR Spectroscopy

Ruthenium: Organometallic ChemistryBased in part on the article Ruthenium: Organometallic Chemistry by Ulrich Koelle which appeared in the Encyclopedia of Inorganic Chemistry, First Edition .

Ruthenium: Organometallic ChemistryBased in part on the article Ruthenium: Organometallic Chemistry by Ulrich Koelle which appeared in the Encyclopedia of Inorganic Chemistry, First Edition .

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