Hydrogen bonding and proton transfer involving the trihydride complexes Cp*M(dppe)H<sub>3</sub>(M = Mo, W) and fluorinated alcohols: the competitive role of the hydride ligands and metal

Andrieu, Jacques; Belkova, Natalia V.; Besora, María; Collange, Edmond; Epstein, Lina M.; Lledós, Agustí; Poli, Rinaldo; Revin, Pavel O.; Shubina, Elena S.; Воронцов, Е. В.

doi:10.1023/b:rucb.0000019886.18334.55

Cited by 13 publications

(19 citation statements)

References 12 publications

(6 reference statements)

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“…Since the results of previous investigations into the protonation of [Cp*Mo(dppe)H 3 ] [13][14][15] serve as a basis for the new findings described in this paper, we summarize here the salient points that emerge from those studies. (i) The trihydride complex has a high basicity factor (E j = 1.42 Ϯ 0.02), placing it in the category of the most hydridic complexes known.…”

Section: Resultsmentioning

confidence: 95%

Solvent Control in the Protonation of [Cp*Mo(dppe)H₃] by CF₃COOH

et al. 2007

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The outcome of the reaction between [Cp*Mo(dppe)H3] [dppe = 1,2‐bis(diphenylphosphanyl)ethane] and trifluoroacetic acid (TFA) is highly dependent on the solvent and the TFA/Mo ratio. The dihydride compound [Cp*Mo(dppe)H2(O2CCF3)] is obtained selectively when the reaction is carried out in aromatic hydrocarbons (benzene, toluene) when using less than one equivalent of TFA. The dihydride is also the end product when THF or MeCN are used as solvent, independent of the TFA/Mo ratio. In benzene/toluene the use of excess acid has a profound effect, resulting in the formation of the tetrahydrido complex [Cp*Mo(dppe)H4]+, which did not further evolve into the dihydrido product. Monitoring of the reaction by NMR and IR spectroscopy under different conditions (solvent, temperature, TFA/Mo ratio) reveals the rapid establishment of an equilibrium between the dihydrogen‐bonded adduct, [Cp*Mo(dppe)H3]···HO2CCF3, the ion‐paired proton‐transfer product, [Cp*Mo(dppe)H4]+···–O2CCF3, and the separated ions, followed by a slower irreversible transformation to the final dihydride product with H2 evolution. The activation parameters of the H2 evolution and M–OR product formation were determined. Excess TFA in low‐polarity solvents stabilizes the separated charged species by forming the homoconjugate anion [CF3COO(CF3COOH)n]–. The effect of the solvent on the course of the reaction can be interpreted in terms of the different polarity, H‐bonding ability, and coordinating power of the various solvent molecules.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

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Section: Resultsmentioning

confidence: 95%

Solvent Control in the Protonation of [Cp*Mo(dppe)H₃] by CF₃COOH

et al. 2007

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“…The cutoff between metal site and hydride site is not so clear in those cases because even for M···H separations of about 2.6 (the usual distance for this kind of interaction) there will also be relatively short H···H separation. These hydrogen bonds could be more appropriately described as bifurcated, [59,63] and the steric effects may play more similar roles for the two types of interactions.…”

Section: Discussionmentioning

confidence: 98%

Experimental and Computational Studies of Hydrogen Bonding and Proton Transfer to [Cp*Fe(dppe)H]

Belkova

Collange

Dub

et al. 2005

Chemistry A European J

133

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The present contribution reports experimental and computational investigations of the interaction between [Cp*Fe(dppe)H] and different proton donors (HA). The focus is on the structure of the proton transfer intermediates and on the potential energy surface of the proton transfer leading to the dihydrogen complex [Cp*Fe(dppe)(H2)]+. With p-nitrophenol (PNP) a UV/Visible study provides evidence of the formation of the ion-pair stabilized by a hydrogen bond between the nonclassical cation [Cp*Fe(dppe)(H2)]+ and the homoconjugated anion ([AHA]-). With trifluoroacetic acid (TFA), the hydrogen-bonded ion pair containing the simple conjugate base (A-) in equilibrium with the free ions is observed by IR spectroscopy when using a deficit of the proton donor. An excess leads to the formation of the homoconjugated anion. The interaction with hexafluoroisopropanol (HFIP) was investigated quantitatively by IR spectroscopy and by 1H and 31P NMR spectroscopy at low temperatures (200-260 K) and by stopped-flow kinetics at about room temperature (288-308 K). The hydrogen bond formation to give [Cp*Fe(dppe)H]HA is characterized by DeltaH degrees =-6.5+/-0.4 kcal mol(-1) and DeltaS degrees = -18.6+/-1.7 cal mol(-1) K(-1). The activation barrier for the proton transfer step, which occurs only upon intervention of a second HFIP molecule, is DeltaH(not equal) = 2.6+/-0.3 kcal mol(-1) and DeltaS(not equal) = -44.5+/-1.1 cal mol(-1) K(-1). The computational investigation (at the DFT/B3 LYP level with inclusion of solvent effects by the polarizable continuum model) reproduces all the qualitative findings, provided the correct number of proton donor molecules are used in the model. The proton transfer process is, however, computed to be less exothermic than observed in the experiment.

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“…E j Cp 2 Ru (0.67) < Cp 2 Os (0.81) and Cp* 2 Ru (0.85) < Cp* 2 Os (1.05)]. [21,70,71] The orbital component of a classical hydrogen bond is of donor-acceptor nature; the lone pair orbital of the base donates electrons to an empty s Ã AH orbital that has its main coeffi- www.chemphyschem.org cient on the protonic hydrogen atom (Figure 9 a). Such increase of the M···H interaction strength for 5d transition metals seems to be a general trend.…”

Section: Discussionmentioning

confidence: 99%

Directionality of Dihydrogen Bonds: The Role of Transition Metal Atoms

Filippov¹,

Belkova²,

Epstein³

et al. 2012

ChemPhysChem

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A theoretical study on two series of electron-rich group 8 hydrides is carried out to evaluate involvement of the transition metal in dihydrogen bonding. To this end, the structural and electronic parameters are computed at the DFT/B3PW91 level for hydrogen-bonded adducts of [(PP(3))MH(2)] and [Cp*MH(dppe)] (M = Fe, Ru, Os; PP(3) = κ(4)-P(CH(2)CH(2)PPh(2))(3), dppe = κ(2)-Ph(2)PCH(2)CH(2)PPh(2)) with CF(3)CH(2)OH (TFE) as proton donor. The results are compared with those of adduct [Cp(2)NbH(3)]⋅TFE featuring a "pure" dihydrogen bond, and classical hydrogen bonds in pyridine⋅TFE and Me(3)N⋅TFE. Deviation of the H⋅⋅⋅H-A fragment from linearity is shown to originate from the metal participation in dihydrogen bonding. The latter is confirmed by the electronic parameters obtained by NBO and AIM analysis. Considered together, orbital interaction energies and hydrogen bond ellipticity are salient indicators of this effect and allow the MH⋅⋅⋅HA interaction to be described as a bifurcate hydrogen bond. The impact of the M⋅⋅⋅HA interaction is shown to increase on descending the group, and this explains the experimental trends in mechanisms of proton-transfer reactions via MH⋅⋅⋅HA intermediates. Strengthening of the M⋅⋅⋅H interaction in the case of electron-rich 5d metal hydrides leads to direct proton transfer to the metal atom.

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Hydrogen bonding and proton transfer involving the trihydride complexes Cp*M(dppe)H₃(M = Mo, W) and fluorinated alcohols: the competitive role of the hydride ligands and metal

Cited by 13 publications

References 12 publications

Solvent Control in the Protonation of [Cp*Mo(dppe)H₃] by CF₃COOH

Solvent Control in the Protonation of [Cp*Mo(dppe)H₃] by CF₃COOH

Experimental and Computational Studies of Hydrogen Bonding and Proton Transfer to [Cp*Fe(dppe)H]

Directionality of Dihydrogen Bonds: The Role of Transition Metal Atoms

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Hydrogen bonding and proton transfer involving the trihydride complexes Cp*M(dppe)H3(M = Mo, W) and fluorinated alcohols: the competitive role of the hydride ligands and metal

Cited by 13 publications

References 12 publications

Solvent Control in the Protonation of [Cp*Mo(dppe)H3] by CF3COOH

Solvent Control in the Protonation of [Cp*Mo(dppe)H3] by CF3COOH

Experimental and Computational Studies of Hydrogen Bonding and Proton Transfer to [Cp*Fe(dppe)H]

Directionality of Dihydrogen Bonds: The Role of Transition Metal Atoms

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Hydrogen bonding and proton transfer involving the trihydride complexes Cp*M(dppe)H₃(M = Mo, W) and fluorinated alcohols: the competitive role of the hydride ligands and metal

Solvent Control in the Protonation of [Cp*Mo(dppe)H₃] by CF₃COOH

Solvent Control in the Protonation of [Cp*Mo(dppe)H₃] by CF₃COOH