The crystal and molecular structure of oxobis(ethane-1,2-diolato)osmium(VI): a five-coordinate diester complex

Phillips, Frederick L.; Skapski, A. C.

doi:10.1107/s0567740875006280

Cited by 27 publications

(5 citation statements)

References 17 publications

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“…We want to point out that compound 6 ( Os ) has been isolated and an X-ray structure analysis of the molecule has been published . The theoretically predicted bond lengths and angles which are presented here and in a previous theoretical study which reported Hartree−Fock geometries are in very good agreement with the experimental data …”

Section: Resultssupporting

confidence: 74%

Why Are Olefins Oxidized by RuO₄under Cleavage of the Carbon−Carbon Bond whereas Oxidation by OsO₄Yieldscis-Diols?

2004

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Quantum chemical calculations using gradient-corrected (B3LYP) density functional theory have been carried out to investigate the mechanism of the oxidative cleavage of alkenes by ruthenium tetraoxide. The initial reaction of the tetraoxide with the olefin occurs via a [3+2] cycloaddition as in the case of osmium tetraoxide. The results clearly show that the bond cleavage does not take place at the primary adduct, but much later in the reaction path. After the formation of the ruthenium(VI)dioxo-2,5-dioxolane, the reaction proceeds with the addition of a second olefin to yield ruthenium(IV)-bis(2,5-dioxolane), which in turn becomes oxidized first to rutheniumoxo(VI)-bis(2,5-dioxolane) 6(Ru) and then to ruthenium(VIII)-dioxo-bis(2,5-dioxolane) 7(Ru). Only in complexes containing the metal center in the formal oxidation state +VIII are low activation barriers for C-C bond cleavage and exothermic formation of carbonyl compounds as products calculated. The lowest activation barrier, DeltaH(++) = 2.5 kcal/mol, is calculated for the C-C bond breaking reaction of 7(Ru) which is predicted as the pivotal intermediate of the oxidation reaction. The calculations of the oxidation reaction with OsO(4) show that those reactions where the oxidation state of the metal increases have larger activation barriers for M = Ru than for M = Os, while reactions which reduce the oxidation state have a lower activation barrier for ruthenium compounds. Also, reactions which increase the oxidation state of the metal are in the case of M = Os more exothermic than for M = Ru. In this work, all important points of the potential energy surface (PES) are reported, and the complete catalytic cycle for the oxidative cleavage of olefins by ruthenium tetraoxide is presented.

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Section: Resultssupporting

confidence: 74%

Why Are Olefins Oxidized by RuO₄under Cleavage of the Carbon−Carbon Bond whereas Oxidation by OsO₄Yieldscis-Diols?

2004

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“…The parameters obtained from the fit are found to be in good agreement with the crystallographic parameters obtained for the parent compound oxobis(ethane-1,2-diolato)osmium(VI), of formula OsO(O 2 C 2 H 4 ) 2 . However, in the solid state structure a splitting in the distances of the four oxygen neighbors and the four carbon contributions is found.…”

Section: Resultssupporting

confidence: 74%

“…In both routes the identification and characterization of the species involved in these sorts of reactions is crucial for understanding the mechanisms. In the past few years several efforts have been made to obtain their structures, mainly as pure compounds in the solid or liquid states, using techniques such as X-ray diffraction, − Raman, − or IR spectroscopy. , The transferability of these results to understanding the active reaction system is not always trivial, as solvent effects are often significant. Furthermore, assumptions that solid and in-solution state structures are interchangeable are also not always valid.…”

Section: Introductionmentioning

confidence: 99%

Determination of the In-Solution Molecular Structure of Reactive Osmium Compounds Involved in the Synthesis of Vicinal Diols

Díaz‐Moreno

Bowron

2002

Organometallics

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Extended X-ray absorption fine structure spectroscopy, EXAFS, has been used to determine the in-solution structure of the two principal reactive components involved in the production of vicinal diols by olefin dihydroxylation using osmium tetroxide. These components are osmium tetroxide (OsO4) and the corresponding diester osmium glycolate complex. The results show that initially the osmium tetroxide molecules are found free and unbound in the investigated solvent (6:1 tertiary butanol in water), with a molecular structure close to that found in the solid state. On addition of an excess of 2,3-dimethyl-2-butene, a compound of formula OsO(O2C6H12)2, a monomeric diester of osmium tetroxide, is formed. The structural refinement of this compound indicates that the osmium center is surrounded by five oxygen atoms, one located at a shorter distance than the other four (1.69 and 1.90 Å, respectively). The same structure has been found for the osmium complex formed as the result of the slow reaction of osmium tetroxide with an excess of ethylene glycol in solution, OsO(O2C2H4)2. This last complex is compared with the known solid state structure.

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“…Furthermore, it was stated that the chemical shift of the methylene group adjacent to the oxygen in 59 and adjacent to the osmium in 60 probably are not as identical as suggested.122 Moreover, it would not be expected that 59 and 60 are formed at nearly equal amounts which is a consequence of the above interpretation.122 Instead of assigning the XH NMR data to the metallaoxetanes, it was proposed that the data are more consistent with a mixture of dimeric osmium(VI) esters,122 which are known to form in the reactions of alkenes with osmium tetraoxide. [123][124][125][126][127] The reaction of alkenes with osmium tetraoxide has been investigated from a theoretical point of view in an attempt to obtain insight into the mechanism. By using extended Huckel calculations the interaction between an alkene and osmium tetraoxide has been studied.128 Some of the frontier orbitals of osmium tetraoxide are shown to the left in Figure 2.…”

Section: Formation and Reactions Of Known Metallaoxetanesmentioning

confidence: 99%

Metallaoxetanes as intermediate in oxygen-transfer reactions - reality or fiction?

Joergensen¹,

Schioett²

1990

Chem. Rev.

201

101

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The crystal and molecular structure of oxobis(ethane-1,2-diolato)osmium(VI): a five-coordinate diester complex

Cited by 27 publications

References 17 publications

Why Are Olefins Oxidized by RuO₄under Cleavage of the Carbon−Carbon Bond whereas Oxidation by OsO₄Yieldscis-Diols?

Why Are Olefins Oxidized by RuO₄under Cleavage of the Carbon−Carbon Bond whereas Oxidation by OsO₄Yieldscis-Diols?

Determination of the In-Solution Molecular Structure of Reactive Osmium Compounds Involved in the Synthesis of Vicinal Diols

Metallaoxetanes as intermediate in oxygen-transfer reactions - reality or fiction?

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The crystal and molecular structure of oxobis(ethane-1,2-diolato)osmium(VI): a five-coordinate diester complex

Cited by 27 publications

References 17 publications

Why Are Olefins Oxidized by RuO4under Cleavage of the Carbon−Carbon Bond whereas Oxidation by OsO4Yieldscis-Diols?

Why Are Olefins Oxidized by RuO4under Cleavage of the Carbon−Carbon Bond whereas Oxidation by OsO4Yieldscis-Diols?

Determination of the In-Solution Molecular Structure of Reactive Osmium Compounds Involved in the Synthesis of Vicinal Diols

Metallaoxetanes as intermediate in oxygen-transfer reactions - reality or fiction?

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Product

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Why Are Olefins Oxidized by RuO₄under Cleavage of the Carbon−Carbon Bond whereas Oxidation by OsO₄Yieldscis-Diols?

Why Are Olefins Oxidized by RuO₄under Cleavage of the Carbon−Carbon Bond whereas Oxidation by OsO₄Yieldscis-Diols?