A hydrogen atom in an organoplatinum-amine system. 2. The first isolated arylplatinum(IV) hydrides: synthetic and theoretical study (SCF and CAS-SCF calculations) on model complexes with a N-M(IV)-H/M(II)-.cntdot..cntdot..cntdot.H-N+ unit (M = Pd, Pt)

Koten, Gerard van; Wehman-Ooyevaar, Ingrid C. M.; Grove, David M.; Vaal, P. de; Dedieu, Alain

doi:10.1021/ic00052a026

Cited by 62 publications

(58 citation statements)

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“…Another example involving a d 10 metal is provided by the adsorption of water on Pt(111), where recent evidence for hydrogen bonds between hydrogen atoms in water and Pt has been presented (30). Extensive experimental and computational evidence has also been provided for the involvement of a PtOHN hydrogen bond in zwitterionic Pt(II) complexes with a properly situated ammonium group (31)(32)(33). By x-ray crystallography an almost linear three-center PtOHN arrangement was observed (34).…”

Section: Resultsmentioning

confidence: 99%

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: Resultsmentioning

confidence: 99%

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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“…* A qualitative description of the bonding in 3c-2e and 3c-4e X--H...M interactions is presented in Fig. 2. * The vacant Pt 6p-orbital is of suitable symmetry to serve as such an acceptor orbital, but is rather high in energy and at best plays a very minor role in the three-centre interaction (Wehman-Ooyevaar, Grove, de Vaal, Dedieu & van Koten, 1992 Examination of the literature revealed a number of square-planar d~-Pt Ix and -Pd ]l complexes which have N--H...M or C--H...M interactions similar to that observed in (1). Compounds (2)-(5) shown in Fig.…”

Section: Introductionmentioning

confidence: 82%

“…For example, van Koten and coworkers have isolated not only (5), but also a ptlV-hydride complex which is related to that which would result from oxidative addition of the N--H bond to the Pt II centre in (5) (Wehman-Ooyevaar, Grove, de Vaal et al, 1992). The ptlV-hydride and (5) were prepared from similar reactions of the Pt(I-C~¢~H6-NMe2-8-C,N) 2 precursor, but oxidative addition/reductive elimination of N--H has not been demonstrated.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen bonds involving transition metal centres – a brief review

Brammer¹,

Zhao²,

Ladipo³

et al. 1995

Acta Crystallogr Sect B

143

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Hydrogen bonding is a topic which has received much attention over the years and continues to do so as the importance of such interactions is established in all areas of chemistry. The class of hydrogen bonds that directly involves electron-rich transition metal centres in the three-centre interaction has received little attention until quite recently. Such interactions are of importance in understanding intermolecular interactions between organometallic molecules and are particularly relevant to understanding proton transfer reactions that directly involve transition metal centres.

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“…[2,3] A possible deprotonation of a s-methane metal complex has been proposed in parallel with the deprotonation of its isomeric methyl hydride (methanido hydrido) complex. [3,5] Although the direct deprotonation of metal hydridoaryl complexes [11][12][13] and of a metal dihydrogen complex [14][15][16][17][18][19] is known, no clear evidence for deprotonation of a s-alkane ligand is available.…”

Section: Introductionmentioning

confidence: 99%

Proton Walk in the Aqueous Platinum Complex [TpPtMeCO] via a Sticky σ‐Methane Ligand

Lo¹,

Iron²,

Martin³

et al. 2007

Chemistry A European J

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Both experimental and theoretical evidence suggest that the proton exchange between water and the methyl group in [TpPt(CO)CH(3)] (1, Tp=hydridotripyrazolylborate) involves the formation and deprotonation of a "sticky" sigma-methane ligand. The efficiency of this nontrivial process has been attributed to the spatial orientation of functional groups that operate in concert to activate a water molecule and then achieve a multistep proton walk from water to an uncoordinated pyrazolyl nitrogen atom, to the methyl ligand, and then back to the nitrogen atom and water. The overall proton-exchange process has been proposed to involve an initial attack of water at the CO ligand in 1 with concerted deprotonation by the uncoordinated pyrazolyl nitrogen atom. The pyrazolium proton is then transferred to the Pt--CH(3) bond, leading to a sigma-methane intermediate. Subsequent rotation and deprotonation of the sigma-methane ligand, followed by reformation of 1 and water, result in scrambling of the methyl protons with the hydrogen atoms of water. An alternative two-step process that involves oxidative addition and reductive elimination has also been considered. The two competing mechanistic routes from 1 into [D(3)]-1, as well as the conversion of 1 into [TpPt(CH(3))H(2)] (2), have been examined by density functional theory (DFT) using a variety of exchange-correlation methods, primarily PW6B95, which was recently shown to be highly accurate for evaluating reactions of late-transition-metal complexes. The key role played by the free pyrazolyl nitrogen atom, acting as a proton carrier that abstracts a proton from water and transfers the proton to the Pt--CH(3) bond, is reminiscent of the dual functionality of histidine in the catalytic triad of natural serine proteases.

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A hydrogen atom in an organoplatinum-amine system. 2. The first isolated arylplatinum(IV) hydrides: synthetic and theoretical study (SCF and CAS-SCF calculations) on model complexes with a N-M(IV)-H/M(II)-.cntdot..cntdot..cntdot.H-N+ unit (M = Pd, Pt)

Cited by 62 publications

References 0 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

Hydrogen bonds involving transition metal centres – a brief review

Proton Walk in the Aqueous Platinum Complex [TpPtMeCO] via a Sticky σ‐Methane Ligand

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