Is intermolecular hydrogen-bonding to uncharged metal centers of organometallic compounds widespread in solution? A spectroscopic investigation in hydrocarbon, noble gas, and supercritical fluid solutions of the interaction between fluoro alcohols and (.eta.5-C5R5)ML2 (R = H, Me; M = Co, Rh, Ir; L = CO, C2H4, N2, PMe3) and its relevance to protonation

Kazarian, Sergei G.; Hamley, Paul A.; Poliakoff, Martyn

doi:10.1021/ja00073a024

Cited by 98 publications

(65 citation statements)

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“…Modeling the equilibrium constants using general chemical-physical analysis results in differences in predicted and experimentally calculated equilibrium constants which are greater than accountable by theory alone. This evidence of solute-cosolvent clustering is consistent with the effects of density on hydrogen bonding (Kazarian et al, 1993). Hydrogen bonding has been shown to decrease with increasing density.…”

Section: Kinetic Data Insupporting

confidence: 81%

“…Recent studies of chemical equilibria have focused on the effects of pressure on the equilibrium constants of solutes in pure supercritical fluids (Yagi, 1993;Kazarian, 1993;Yamasaki, 1990). The presence of a cosolvent complicates the system, especially if the cosolvent is capable of participating in specific interactions with the solute molecule and leads to multiple equilibria.…”

Section: Keto-enol Equilibrium Measurementsmentioning

confidence: 99%

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Supercritical Fluid Reactions for Coal Processing

Eckert¹

1997

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Section: Kinetic Data Insupporting

confidence: 81%

Section: Keto-enol Equilibrium Measurementsmentioning

confidence: 99%

Supercritical Fluid Reactions for Coal Processing

Eckert¹

1997

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“…The electron-rich metal center serves as the hydrogen bond acceptor. This type of hydrogen bond is commonly found in the solid state, but it has also been observed in solution (28). To our knowledge, no report of hydrogen bonds involving Pd(0) has appeared, although Ni(0) has been shown theoretically to act as hydrogen bond acceptor (29).…”

Section: Resultsmentioning

confidence: 58%

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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“…[1][2][3] Recently, several authors reported that filled d orbitals of square-planar d 8 metal ions can also act as hydrogen-bond acceptors. [4][5][6][7][8] In particular, a number of square-planar Pt II compounds provide structural evidence for N À H···Pt, O À H···Pt, and C À H···Pt hydrogen bonds. [7][8][9] In most cases the hydrogen bonding is either intramolecular or/ and involves an anionic platinum center.…”

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confidence: 99%

Dispersion‐Driven Hydrogen Bonding: Predicted Hydrogen Bond between Water and Platinum(II) Identified by Neutron Diffraction

et al. 2010

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An alternative to classical? In square‐planar d8 complexes the metal ion can interact with axial H2O molecules either as a Lewis acid or as a Lewis base. Ab initio calculations predicted that uncharged PtII complexes form a hydrogen‐bond‐like interaction with H2O, in which PtII acts as a Lewis base. Such a nonclassical OH⋅⋅⋅Pt hydrogen bond has now been identified in crystals of trans‐[PtCl2(NH3)(N‐glycine)]⋅H2O by neutron diffraction.

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Cited by 98 publications

References 0 publications

Supercritical Fluid Reactions for Coal Processing

Supercritical Fluid Reactions for Coal Processing

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

Dispersion‐Driven Hydrogen Bonding: Predicted Hydrogen Bond between Water and Platinum(II) Identified by Neutron Diffraction

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