Hydrogen-bonded complexes involving the metal atom and protonation of metallocenes of the iron subgroup

Shubina, Elena S.; Крылов, А. Н.; Kreindlin, A. Z.; Rybinskaya, M. I.; Epstein, Lina M.

doi:10.1016/0022-328x(94)87063-2

Cited by 34 publications

(29 citation statements)

References 6 publications

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“…For simplicity, it can be assumed that D L ≈ D LH þ , that then yields pK DCE a ¼ 6.5. These results show that the forward current wave results from an assisted proton transfer by osmocene in the organic phase where the protonation of osmocene forms the corresponding hydride complex (19) as confirmed by NMR studies (vide infra). The return peak in the back scan can be ascribed to the interfacial deprotonation of osmocene hydride.…”

Section: Ion Transfer Voltammetrymentioning

confidence: 66%

Biphasic water splitting by osmocene

Todorova

Patır

et al. 2012

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

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The photochemical reactivity of osmocene in a biphasic waterorganic solvent system has been investigated to probe its water splitting properties. The photoreduction of aqueous protons to hydrogen under anaerobic conditions induced by osmocene dissolved in 1,2-dichloroethane and the subsequent water splitting by the osmocenium metal-metal dimer formed during H 2 production were studied by electrochemical methods, UV-visible spectrometry, gas chromatography, and nuclear magnetic resonance spectroscopy. Density functional theory computations were used to validate the reaction pathways.S olar water splitting is undoubtedly a key challenge (1-3), and in the quest for solar fuels, hydrogen is definitely a major target with many industrial applications ranging from transportation to carbon dioxide mitigation (4).Interestingly, some transition metal complexes like metallocenes have been reported to reduce protons to hydrogen. In 1988, cobaltocene was found to produce hydrogen in strong acidic solutions. The mechanism was investigated by pulse radiolysis, and it was found that the reaction kinetics was first order with respect to cobaltocene and the protons pointing to a protonation of the metal as the primary step (5). In 2009, Kunkely and Vogler reported that osmocene dissolved in strong acidic solutions could photogenerate hydrogen and that ½Cp 2 Os IV ðOH − Þ þ could photogenerate oxygen (6). Proton reduction was shown to proceed also by the formation of a hydride followed under UV light by the formation of H 2 and the dimer ½Cp 2 Os III -Os III Cp 2 2þ .One of the major difficulties in studying water splitting by metallocenes is their very poor solubility in aqueous or even acidic solutions. When investigating the reduction of protons in organic phases where metallocenes are soluble, the other major drawback is the low solubility and dissociation of acids in organic solvents. One way to circumvent these issues is to carry out these reactions in biphasic systems.In 2008, we studied the reduction of aqueous protons by decamethylferrocene (DMFc) in 1,2-dichloroethane (1,2-DCE), and, here again the data suggested that the first step is the protonation of the metal (7). In particular, we have shown that hydrogen bubbles can form at the interface and that hydrogen production is associated to the oxidation of the electron donor DMFc. More generally, we have shown that voltammetry at the interface between two immiscible electrolyte solutions (ITIES) is a very useful tool to study proton coupled electron transfer reactions involving aqueous protons and organic electron donors (8-10). This methodology has been also applied to molecular electrocatalysis where an amphiphilic catalyst is used to complex oxygen to facilitate its reduction as recently reviewed (10-13).In this study, the photochemical reactivity of osmocene with water in biphasic systems has been investigated by electrochemical methods on solid electrodes and soft liquid-liquid interfaces to unravel the multistep reaction mechanisms. Density functional theory (DFT)...

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Section: Ion Transfer Voltammetrymentioning

confidence: 66%

Biphasic water splitting by osmocene

Todorova

Patır

et al. 2012

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

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“…By a subsequent hydrogen abstraction the well known hydride complex [OsCp 2 H] + [22] could be formed (5):…”

Section: + H 2 ð1þmentioning

confidence: 99%

Dehydrogenation of 1,3-cyclohexadiene photocatalyzed by osmocene

Kunkely

Vogler

2010

Inorganic Chemistry Communications

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“…Additional stabilization originated from the contact between the dihydrogen ligand and the counter-ion. Structural elucidation of quite a few examples of these intermediates allowed for the generalization of the mechanism of the proton transfer processes under consideration [47,48,3]. NMR spectroscopic evidence for the MHÁÁÁHX hydrogen bonding is acquired by upfield shifts of the hydride resonance and a decrease of the relaxation times (T 1min ) [12].…”

Section: Introductionmentioning

confidence: 99%

“…The superior methodologies to examine these interactions include variable temperature (VT) IR and NMR spectroscopic studies, X-ray and neutron diffraction studies and supporting density functional theory (DFT) calculations. Crabtree's group observed intermolecular dihydrogen bonding in the crystal of the rhenium complex Re-H 5 (PPh 3 ) 3 Áindole by an X-ray diffraction study [38][39][40][41]. Based on HÁÁÁH bond distances and their corresponding bond angles, the strength of the HÁÁÁH bond and linearity of the HÁÁÁHRe fragments could be established.…”

Section: Introductionmentioning

confidence: 99%