1H and 13C NMR study of low-energy intramolecular transformations of coordinated propargyl cations [(μ-η2-η3-HCCCR1R2)Cp2Mo2(CO)4]+BF4−

Galakhov, M. V.; Bakhmutov, Vladimir I.; Barinov, I. V.; Reutov, O. A.

doi:10.1016/0022-328x(91)86432-p

Cited by 15 publications

(6 citation statements)

References 13 publications

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“…) 17, 14, and 10 Kcal/mol, respectively. 115 Although there is no crystallographic data reported for [Co 2 ] isolobal cations, their structures, however, were proposed on the basis of NMR analysis. 72 For secondary or tertiary cations possessing nonequivalent or achiral substituents two parameters should be considered to determine the chirality of the species: (a) the chirality of the cluster core, and (b) the chirality of the carbenium center as a consequence of the metal carbenium C + interaction leading to a tetrahedral carbon.…”

Section: Uncharged Bimetallic Acetylenic Complexesmentioning

confidence: 99%

“…) in solid state and in solution at low temperature allow the unambiguous determination of the chemical shifts for the carbons in each diastereomer. 115 [Mo 2 ] propargylium ions possessing chiral ligands, for instance ethynylmestranol 87 or propynylborneol, 91 were also investigated. In these cases it was demonstrated by 1 H NMR analysis that the diastereomeric ratio is influenced by steric factors.…”

Section: Uncharged Bimetallic Acetylenic Complexesmentioning

confidence: 99%

“…Thus the free energy for the fluxional processes decreases as the distance d (M−C + ) increases. From primary to tertiary [Mo 2 Cp 2 (CO) 4 (μ-η 2 ,η 3 -HC⋮CC(R 1 R 2 )][BF 4 ] (R 1 = R 2 = H; R 1 = H, R 2 = CH 3 ; R 1 = R 2 = CH 3 ) cations the distances d (M−C + ) were found to be 2.47, 2.63, and 2.74 Å, respectively, while the corresponding free activation energies were determined as Δ G # = 17, 14, and 10 Kcal/mol, respectively …”

Section: Carbenium Ions Stabilized By Acetylenic Bimetallic Clustermentioning

confidence: 99%

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New Bonding Modes, Fluxional Behavior, and Reactivity in Dinuclear Complexes Bridged by Four-Electron Donor Unsaturated Hydrocarbons

1996

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Section: Uncharged Bimetallic Acetylenic Complexesmentioning

confidence: 99%

Section: Uncharged Bimetallic Acetylenic Complexesmentioning

confidence: 99%

Section: Carbenium Ions Stabilized By Acetylenic Bimetallic Clustermentioning

confidence: 99%

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New Bonding Modes, Fluxional Behavior, and Reactivity in Dinuclear Complexes Bridged by Four-Electron Donor Unsaturated Hydrocarbons

1996

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“…cation there are intimations of a very low-energy fluxional process in which extra cyclopentadienyl resonances are observed. Subsequently, there has been speculation about the possibility of evaluating the barrier to rotation of the (C,H,)Mo(CO), vertices (19).…”

Section: Resultsmentioning

confidence: 99%

A variable-temperature ¹³C NMR study of (η⁵-C₅H₅)₂Mo₂(CO)₄ complexes of chiral alkynes derived from a terpene or a hormonal steroid: interconversion of diastereomers via exchange of terminal and semi-bridging carbonyls

Tondu¹,

Jaouen²,

D'Agostino³

et al. 1992

Can. J. Chem.

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the steroidal hormone 11P-(4-dimethylaminopheny1)-17P-hydroxy-17a-(1-propyny1)-estra-4,9-dien-3-one (RU 38486) or with propynylborneol yields in each case a chiral cluster that exhibits two cyclopentadienyl resonances in both the 'H and I3c NMR regimes. At low temperature the interconversion of diastereomers arising from the different orientations of the semi-bridging carbonyl ligand can be slowed on the NMR time scale. The barrier to diastereomer interchange has been determined for the terpenoid cluster and the mechanism of this process is discussed. La reaction du (C,H,)IMo,(CO)4 avec l'hormone steroidale 11~-(4-dim~thylamino)-17~-hydroxy-17a-(l-propynyl)-estra-4,9-dikn-3-one (RU 38486) ou avec le propynylborneol conduit dans chaque cas h un cluster chiral qui presente deux resonances de cyclopentadienyles en RMN tant du 'H que du I3c. A basses temperatures, sur 17Cchelle de temps de la RMN, on peut ralentir l'interconversion des diaster~oisom&res provenant des differentes orientations dans le ligand carbonyle agissant comme demi-pont.[Traduit par la redaction]

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“…(4) A parallel can be made between the above results which show the effect of the R1 and R2 ligands on the reduction mechanism of the [Mo 2 Cp 2 (CO) 4 {μ-η 2 :η 3 -HC⋮C−C(R1)(R2)}] + compounds and the studies of the fluxional processes in these complexes. It has been demonstrated that the energy barrier to isomerization decreases as the Mo1···C5 separation increases …”

Section: Discussionmentioning

confidence: 99%

Electrochemistry of [Mo₂Cp₂(CO)₄{μ-η²:η³-HC⋮C−C(R1)(R2)}]⁺Complexes (R1 = H, R2 = H, Me, Et, Fc; R1 = Me, R2 = Me, Ph). Control of the Reduction Process (Two-ElectronvsOne-Electron) by the Substituents R1 and R2: EHMO Rationalization

Capon¹,

Kergoat²,

Berre-Cosquer³

et al. 1997

Organometallics

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The electrochemical reduction of [Mo2Cp2(CO)4{μ-η2:η3-HC⋮C−C(R1)(R2)}]+ complexes has been investigated by cyclic voltammetry, controlled-potential electrolysis, and coulometry. On the cyclic voltammetry time scale, the complexes with R1 = H, R2 = H (1 + ), Me (2 + ), Et (3 + ) undergo an irreversible or a quasi-reversible one-electron reduction whereas the analogues with R1 = H, R2 = Fc (4 + ) and R1 = Me, R2 = Me (5 + ) and Ph (6 + ) reduce in a single-step, reversible or quasi-reversible, two-electron process. Two different chemical reactions are involved in the overall reduction mechanism. The first chemical step is assigned as a structural rearrangement, responsible for slowing down the heterogeneous electron transfer. Extended Hückel MO calculations indicate that in the case of the complexes with R1 = H, R2 = Fc and R1 = Me, R2 = Me or Ph, a small increase in the distance between one metal center and the carbon of the C(R1)(R2) group could trigger the two-electron transfer process. The second chemical reaction leading to the final product(s) of the reduction involves radical species, even when a two-electron transfer is observed by cyclic voltammetry. The final products formed in these processes have been identified either by 1H NMR spectroscopy of the compounds extracted from the catholyte after controlled-potential electrolyses or from a comparison of their characteristic redox potentials with those of authentic samples. The nature of the final product(s), either a dimer or μ-alkyne and μ-enyne complexes, is also dependent on the nature of R1 and R2.

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1H and 13C NMR study of low-energy intramolecular transformations of coordinated propargyl cations [(μ-η2-η3-HCCCR1R2)Cp2Mo2(CO)4]+BF4−

Cited by 15 publications

References 13 publications

New Bonding Modes, Fluxional Behavior, and Reactivity in Dinuclear Complexes Bridged by Four-Electron Donor Unsaturated Hydrocarbons

New Bonding Modes, Fluxional Behavior, and Reactivity in Dinuclear Complexes Bridged by Four-Electron Donor Unsaturated Hydrocarbons

A variable-temperature ¹³C NMR study of (η⁵-C₅H₅)₂Mo₂(CO)₄ complexes of chiral alkynes derived from a terpene or a hormonal steroid: interconversion of diastereomers via exchange of terminal and semi-bridging carbonyls

Electrochemistry of [Mo₂Cp₂(CO)₄{μ-η²:η³-HC⋮C−C(R1)(R2)}]⁺Complexes (R1 = H, R2 = H, Me, Et, Fc; R1 = Me, R2 = Me, Ph). Control of the Reduction Process (Two-ElectronvsOne-Electron) by the Substituents R1 and R2: EHMO Rationalization

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1H and 13C NMR study of low-energy intramolecular transformations of coordinated propargyl cations [(μ-η2-η3-HCCCR1R2)Cp2Mo2(CO)4]+BF4−

Cited by 15 publications

References 13 publications

New Bonding Modes, Fluxional Behavior, and Reactivity in Dinuclear Complexes Bridged by Four-Electron Donor Unsaturated Hydrocarbons

New Bonding Modes, Fluxional Behavior, and Reactivity in Dinuclear Complexes Bridged by Four-Electron Donor Unsaturated Hydrocarbons

A variable-temperature 13C NMR study of (η5-C5H5)2Mo2(CO)4 complexes of chiral alkynes derived from a terpene or a hormonal steroid: interconversion of diastereomers via exchange of terminal and semi-bridging carbonyls

Electrochemistry of [Mo2Cp2(CO)4{μ-η2:η3-HC⋮C−C(R1)(R2)}]+Complexes (R1 = H, R2 = H, Me, Et, Fc; R1 = Me, R2 = Me, Ph). Control of the Reduction Process (Two-ElectronvsOne-Electron) by the Substituents R1 and R2: EHMO Rationalization

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A variable-temperature ¹³C NMR study of (η⁵-C₅H₅)₂Mo₂(CO)₄ complexes of chiral alkynes derived from a terpene or a hormonal steroid: interconversion of diastereomers via exchange of terminal and semi-bridging carbonyls

Electrochemistry of [Mo₂Cp₂(CO)₄{μ-η²:η³-HC⋮C−C(R1)(R2)}]⁺Complexes (R1 = H, R2 = H, Me, Et, Fc; R1 = Me, R2 = Me, Ph). Control of the Reduction Process (Two-ElectronvsOne-Electron) by the Substituents R1 and R2: EHMO Rationalization