New types of hydrogen bonding in organometallic chemistry

Epstein, Lina M.; Shubina, Elena S.

doi:10.1016/s0010-8545(02)00118-2

Cited by 276 publications

(197 citation statements)

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“…The palladium-hydrogenoxygen angles involving the hydroxy groups situated closest to palladium were found to be 149.4°and 157.3°. These results, together with the observed stabilization of the transition state in reactions with the hydroxy-containing ligands, are consistent with the interpretation of the interaction as a hydrogen bond (22) and exclude metal-coordinated ligand interacting by means of the oxygen lone pair.…”

Section: Resultssupporting

confidence: 87%

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OH–Pd(0) interaction as a stabilizing factor in palladium-catalyzed allylic alkylations

Hallman

Frölander²,

Wondimagegn³

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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In palladium-catalyzed alkylations of allylic acetates with malonate as nucleophile, catalysts with oxazoline ligands bearing hydroxymethyl substituents in 4-position have been shown by density functional theory computations to undergo a conformational change on nucleophilic attack, which is accompanied by reduction of Pd(II) to Pd(0). The conformations of the Pd(0) complexes were shown to be governed by the presence of a hydrogen bond with the metal center acting as a hydrogen bond acceptor. The conformational change, which is absent in catalysts with O-alkylated analogs, largely affects the enantioselectivity of the catalytic process. This process is a previously uninvestigated example of where this type of weak hydrogen bond has been shown to influence the stereochemistry of a chemical reaction.A symmetric metal catalysis constitutes a powerful method for the preparation of enantiopure chiral compounds (1-3). To achieve high selectivity in the catalytic reactions, proper design of chiral ligands having the ability to transfer the chiral information to the reacting substrates is required. Proper design is usually accomplished by consideration of the steric and electronic demands of the catalytic process under study. Secondary interactions between the chiral ligand and the reacting species may influence the conformation of the catalyst, thereby affecting the stereoselectivity (4). At the same time, such interactions may be used to tune the electronic properties, resulting in increased reactivity of the catalytic system. Several examples of increased stereoselectivity and͞or acceleration of catalytic processes by ligands containing properly situated hydroxy groups have been reported. In rhodium-catalyzed hydrogenations of olefins, hydroxy substituents in the ligands have been shown to have remarkable effects. Thus, Knowles et al. (5) observed that a (R,R)-1,2-ethanediylbis[(2-methoxyphenyl)-phenylphosphine] derivative with the methoxy groups replaced by hydroxy groups provided high enantioselectivity, although it was at the expense of the high reactivity. Later, Börner (ref. 6 and references cited therein) noted similar effects for other types of ligands and provided evidence that properly situated hydroxy groups in the ligands coordinate to the cationic rhodium center by their oxygen lone pairs. Hayashi and coworkers (7-9) observed an accelerating effect by hydroxy groups in palladium-catalyzed allylic alkylations by using ferrocenylphosphine ligands. The effect was believed to be caused by an attractive interaction involving hydrogen bonding between a hydroxy group in the ligand and the nucleophile.We recently found that use of 2-(1-hydroxyalkyl)-(1a) and 2-(1-alkoxyalkyl)pyridinooxazolines (1b) as ligands in palladium-catalyzed allylic alkylations with malonate resulted in profoundly different enantioselectivities, ligands with (R*,R*)-configuration of the former type and those with (R*,S*)-configuration of the latter type, resulting in higher enantioselectivity than their diastereomers (10). This difference...

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Section: Resultssupporting

confidence: 87%

“…Interactions between protons bound to oxygen or nitrogen and late transition metals in low oxidation states have lately been observed in several cases (22)(23)(24)(25)(26). The interaction exhibits features similar to those of the classical hydrogen bond (27), with elongated OOH bonds, short MOH distances, and large OOHOM bond angles.…”

Section: Resultsmentioning

confidence: 95%

OH–Pd(0) interaction as a stabilizing factor in palladium-catalyzed allylic alkylations

Hallman

Frölander²,

Wondimagegn³

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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“…The equilibrium shifts toward the latter product with lowering pH (5.9 → 3.6). 31 In the gas phase, the dihydrido compound trans-[CpRu(H) 2 The low temperature proton transfer of the related Cp*RuH(PPh 2 py) 2 hydride was shown 33 to yield the classical dihydride as well as the DHB species RuH⋅HN. According to DFT calculations, the cause of this behavior is the facile protonation of the pyridine nitrogen atoms, which (after possible rotations around Ru-P and P-C(py) bonds) results in structures with pyH + ⋅⋅⋅py hydrogen bonds.…”

Section: Methodsmentioning

confidence: 99%

“…1,2 This is due to their importance for basic processes such as enzymatic dihydrogen evolution or catalytic ionic hydrogenation. 3 Hydrogen bonding is one of the weak interactions often invoked in molecular recognition or supramolecular assembly design.…”

Section: Introductionmentioning

confidence: 99%

On the peculiarities of hydrogen bonding and proton transfer equilibria for organic vs organometallic bases

Belkova¹,

Epstein²,

Shubina³

2008

Arkivoc

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This review summarizes experimental and theoretical results on hydrogen bonding (HB) and proton transfer processes involving organometallic bases (especially transition metal hydrides) in comparison with organic bases. The competition between different sites for HB and protonation, the proton accepting ability and the HB enthalpy dependence on the atom position in the Periodic Table, proton affinity values and features of proton transfer potential energy profiles are displaying peculiarities of the organometallic bases as proton acceptors.

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“…For example, it has been shown that metals in certain cases can be hydrogen-bond acceptors [23,24]. Moreover, the effect of metal ions on water structure has been thoroughly studied by both experimental and theoretical methods [25,26,27,28,29,30].…”

Section: Introductionmentioning

confidence: 99%

How are hydrogen bonds modified by metal binding?

Husberg

Ryde

2013

J Biol Inorg Chem

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How are hydrogen bonds modified by metal binding?Husberg, Charlotte; Ryde, Ulf General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. AbstractWe have used density-functional theory calculations to investigate how the hydrogenbond strength is modified when a ligand is bound to a metal, using over 60 model systems involving six metals and eight ligands frequently encountered in metalloproteins. We study how the hydrogen-bond geometry and energy vary with the nature of metal, the oxidation state, the coordination number, the ligand involved in the hydrogen bond, other first-sphere ligands, and different hydrogen-bond probe molecules. The results show that in general, the hydrogen-bond strength is increased for neutral ligands and decreased for negatively charged ligands. The size of the effect is mainly determined by the net charge of the metal complex and all effects are typically decreased when the model is solvated. In water solution, the hydrogen-bond strength can increase by up to 37 kJ/mol for neutral ligands, and that of negatively charged ligands can both increase (for complexes with a negative net charge) or decrease (for positively charged complexes). If the net charge of the complex does not change, there is normally little difference between different metals or different types of complexes. The only exception is observed for sulphur-containing ligands (Met and Cys) and if the ligand is redox active (e.g. high-valent Fe-O complexes).Key Words: hydrogen bonds, metalloproteins, quantum-mechanical calculations, densityfunctional theory, dispersion correction, solvation. 2 IntroductionHydrogen bonds play an important role in all types of biochemical systems, strongly affecting catalysis, ligand binding, and enzyme function, for example [1]. They have been thoroughly studied by a variety of experimental and theoretical methods [2,3,4,5,6,7,8,9,10,11,12,13,14,15] so that the strengths of the common hydrogen bonds in biological systems are accurately known.However, it is well-known that metal sites affect the properties of bound ligands. For example, the pK a value of water in aqueous metal complexes is reduced from 15.7 for bulk water, to 12.8 for Ca 2+ and to 2.2 for Fe 3+ [16]. Therefore, it is also likely that metal ions also change the strength and structure of hydrogen bonds inv...

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New types of hydrogen bonding in organometallic chemistry

Cited by 276 publications

References 100 publications

OH–Pd(0) interaction as a stabilizing factor in palladium-catalyzed allylic alkylations

OH–Pd(0) interaction as a stabilizing factor in palladium-catalyzed allylic alkylations

On the peculiarities of hydrogen bonding and proton transfer equilibria for organic vs organometallic bases

How are hydrogen bonds modified by metal binding?

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