Reversible activation of covalent molecules by transition-metal complexes. The role of the covalent molecule

Vaska, L.

doi:10.1021/ar50011a003

Cited by 393 publications

(187 citation statements)

References 21 publications

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“…The activation parameters (AH* = 55 kJ, AS* = -11 5 J K-') are quite typical of those observed for oxidative addition reactions at one metal centre (25)(26)(27)), but we are unaware of any useful, comparable data for dinuclear systems. For the present PdZ1+ PdZI1 system, formation of a species such as lb' necessitates breaking the Pd-Pd bond but the electronic promotional energy (25)(26)(27)) is now only for a single electron at each Pd centre and will be less than that required for 2e-oxidative addition at one "comparable" metal centre; the other factors contributing to AH* are breaking of an S-H bond and formation of the Pd-H and Pd-SH bonds.…”

Section: Discussionmentioning

confidence: 67%

“…The reactivity trend of 1 toward H2S (X = C1 > Br > I) is opposite to that normally encountered for oxidative addition of gas molecules to single metal centres, where more basic auxillary ligands promote reaction (25)(26)(27). Within 1, the Pd-Pd bond strength is expected to increase in the order I < Br < C1 (16), the reverse of the trans effect of the halides (32), and thus the reactivity trend is not dominated by differences in the metal-metal bond strength.…”

Section: Using V(s-h)mentioning

confidence: 61%

“…For the present PdZ1+ PdZI1 system, formation of a species such as lb' necessitates breaking the Pd-Pd bond but the electronic promotional energy (25)(26)(27)) is now only for a single electron at each Pd centre and will be less than that required for 2e-oxidative addition at one "comparable" metal centre; the other factors contributing to AH* are breaking of an S-H bond and formation of the Pd-H and Pd-SH bonds. Overall, the activation parameters for the oxidative addition process for the same molecule at one or two metal centres may turn out to be similar.…”

Section: Discussionmentioning

confidence: 94%

“…Warming an nrnr tube containing a lower frozen layer of a CH2C12 solution of l b and an upper layer of frozen H2S generated a green colour in the upper part but only in the narrow temperature range of about -78 to -60°C. The dielectric constants at -65OC (34) of CH2C12 (E = 15), and of liquid H2S (E = 9), are very similar and the difference in solvent polarity is unlikely to affect the rate (oxidative addition of polar molecules are typically enhanced in more polar media (25)(26)(27)). We consider ourselves fortunate to detect the green hydrides -it appears the oxidative addition is detected, perhaps because of high [H2S], or perhaps because a reverse rate (k-I or k-, , step) is slowed down sufficiently at the low temperature.…”

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confidence: 99%

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Mechanistic aspects of the reaction of hydrogen sulfide with dinuclear palladium(I) complexes containing bis(diphenylphosphino)methane and related ligands

Barnabas¹,

Sallin²,

James³

1989

Can. J. Chem.

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Kinetic and low temperature nmr data are presented for the reaction of hydrogen sulfide with PdzX2(k-dpm)2 species in dichloromethane solution (X = halide, dpm = bis(dipheny1phosphino)methane. The reactions form the corresponding bridgedsulfide, A-frame complex via oxidative-addition of H2S across the Pd-Pd bond to give a hydrido(mercapto) intermediate, that subsequently liberates H, to give Pd2X2(p-S) (~-d p m )~ species. Quantitative kinetic data showing first order behaviour in both Pd2 dimer and H2S concentrations are given for the bromide system over the temperature range 0-3S°C, as well as more limited data for the photosensitive iodide system; plausible mechanisms are discussed. Some qualitative findings are presented for related systems containing 1 ,1-bis(dipheny1phosphino)ethane.Key words: palladium complexes, hydrogen sulfide, bis(dipheny1phosphino)methane.A. FREDDY BARNABAS, DOMINIQUE SALLIN et BRIAN R. JAMES. Can. J. Chem. 67,2009Chem. 67, (1989.On prksente des donnkes relatives a la cinktique ainsi qu'i la rmn a basse tempkrature pour la rkaction du sulfure d'hydrogkne avec les espkces Pd2X2(k-dpm)2 (dans lesquelles X = halogknure et dpm = bis(diphknylphosphino)mkthane), en solution dans le dichloromkthane. Par le biais d'une addition oxydative du H2S a travers la liaison Pd-Pd, les rkactions foment le complexe correspondant, de structure en A et comportant un pont sulfure, qui conduit a un intermkdiaire hydrido(mercapto) et qui libkie par la suite du H2 pour foumir des espkces Pd2X2(k-S) ( k -d~r n )~. Des donnkes cinktiques quantitatives dkmontrent que, pour le systkme du bromure i d e s ternpkratures allant de 0 a 30°C et pour des donnkes plus limitkes relatives au systkme photosensibilisk de l'iodure, les rkactions sont du premier ordre relativement aux concentrations tant du dimkre Pd2 que du H2S; on discute de divers mkcanismes plausibles. On presente quelques donnkes qualitatives concemant des systkmes apparentks contenant du 1 , 1-bis(diphCny1phosphino)Cthane.

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Section: Discussionmentioning

confidence: 67%

Section: Using V(s-h)mentioning

confidence: 61%

Section: Discussionmentioning

confidence: 94%

mentioning

confidence: 99%

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Mechanistic aspects of the reaction of hydrogen sulfide with dinuclear palladium(I) complexes containing bis(diphenylphosphino)methane and related ligands

Barnabas¹,

Sallin²,

James³

1989

Can. J. Chem.

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“…In 1968 Vaska noticed that the oxidative addition of HCl to Vaska´s complex IrCl(CO)(PPh 3 ) 2 is reversible, 23 which persuaded us to investigate whether complex 1 would have similar chemical properties. In a CDCl 3 solution of 1, HCl was formed in situ from ethanol and acetyl chloride.…”

Section: Resultsmentioning

confidence: 99%

Experimental and Theoretical Mechanistic Investigation of the Iridium-Catalyzed Dehydrogenative Decarbonylation of Primary Alcohols

et al. 2015

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ABSTRACT:The mechanism for the iridium-BINAP catalyzed dehydrogenative decarbonylation of primary alcohols with the liberation of molecular hydrogen and carbon monoxide was studied experimentally and computationally. The reaction takes place by tandem catalysis through two catalytic cycles involving dehydrogenation of the alcohol and decarbonylation of the resulting aldehyde. The square planar complex IrCl(CO)(rac-BINAP) was isolated from the reaction between [Ir(cod)Cl] 2 , rac-BINAP and benzyl alcohol. The complex was catalytically active and applied in the study of the individual steps in the catalytic cycles. One carbon monoxide ligand was shown to remain coordinated to iridium throughout the reaction and release of carbon monoxide was suggested to occur from a dicarbonyl complex. IrH 2 Cl(CO)(rac-BINAP) was also synthesized and detected in the dehydrogenation of benzyl alcohol. In the same experiment, IrHCl 2 (CO)(rac-BINAP) was detected from the release of HCl in the dehydrogenation and subsequent reaction with IrCl(CO)(rac-BINAP). This indicated a substitution of chloride with the alcohol to form a square planar iridium alkoxo complex that could undergo a β-hydride elimination. A KIE of 1.0 was determined for the decarbonylation and 1.42 for the overall reaction. Electron rich benzyl alcohols were converted faster than electron poor alcohols, but no electronic effect was found when comparing aldehydes of different electronic character. The lack of electronic and kinetic isotope effects implies a rate determining phosphine dissociation for the decarbonylation of aldehydes.

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Mechanisms of Reaction of Organometallic Complexes

Atwood

Rosenberg

2005

Encyclopedia of Inorganic Chemistry

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An overview of the mechanistic features of organometallic reactions is presented. The primary mechanistic types discussed are ligand substitution, oxidative addition, reductive elimination, and electron transfer. Each reaction pathway is discussed within the context of the common electron counts encountered for most organometallic complexes. Examples of how these common reaction pathways extend to polynuclear complexes are also presented. Although reasonable generalizations with regard to overall reaction rates and stepwise mechanisms using the electron count formalism can be made, many recent reports point out that the details of ligand and metal center structure can override these general trends. A considerable amount of quantitative rate data is provided and computational methodologies for understanding the observed rates are discussed.

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Reversible activation of covalent molecules by transition-metal complexes. The role of the covalent molecule

Cited by 393 publications

References 21 publications

Mechanistic aspects of the reaction of hydrogen sulfide with dinuclear palladium(I) complexes containing bis(diphenylphosphino)methane and related ligands

Mechanistic aspects of the reaction of hydrogen sulfide with dinuclear palladium(I) complexes containing bis(diphenylphosphino)methane and related ligands

Experimental and Theoretical Mechanistic Investigation of the Iridium-Catalyzed Dehydrogenative Decarbonylation of Primary Alcohols

Mechanisms of Reaction of Organometallic Complexes

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