The protonation mechanism of metallocenes and [1.1]metallocenophanes

Mueller‐Westerhoff, Ulrich T.; Haas, Thomas J.; Swiegers, Gerhard F.; Leipert, Thomas K.

doi:10.1016/0022-328x(94)80210-6

Cited by 41 publications

(61 citation statements)

References 49 publications

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“…1,2 It is of interest because of the fluxional behaviour of protonated ferrocene in solution 3 and the reaction is a prototype for electrophilic attack. Although it is the simplest electrophilic chemical reaction of ferrocene, there is still a debate concerning (i) the reaction mechanism, (ii) the possible structures of the protonated molecule and (iii) their relative energies.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of protonated ferrocene isomers in the gas phase and their study by mass spectrometry

Mason¹,

Kelly²

2012

Arkivoc

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Gas phase protonation of ferrocene has been studied experimentally in four different reaction systems, using high energy Collision Induced Decomposition mass spectrometry to follow the progress of reaction at different temperatures and pressures. Experimental evidence is obtained for the existence of three stable isomers as predicted theoretically. The most stable form is shown to be most probably metal-protonated, but the energies of the metal-protonated and agostic forms are within 10 kJ mol -1 of each other. The ring-protonated isomer is higher in energy by ≤ 62 kJ mol -1 . Intramolecular isomerization could not be detected, indicating relatively high energy or entropy barriers separating the isomers. The intermediate complex formed by exo attack of t-C 4 H 9 + on ferrocene was also studied and observed to change structure, from a σ-to a π-complex, leading to the population of different protonated isomers of ferrocene, depending on the temperature.

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Section: Introductionmentioning

confidence: 99%

Synthesis of protonated ferrocene isomers in the gas phase and their study by mass spectrometry

Mason¹,

Kelly²

2012

Arkivoc

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“…This resulted in a very much slower rate of catalytic hydrogen generation from 1 M strong acids. The mixed tetramer 20 involving opposing ferrocene and ruthenocene groups, displayed an even slower, but still measurable catalytic rate [44]. The catalysis was entirely due to interactions between opposing protonated ferrocenes during flexing.…”

Section: Tethered Ferrocene Catalystsmentioning

confidence: 95%

“…A wide range of mono-and di-ferrocene compounds have been prepared and studied, including 10-14 (Scheme 8) [36,37]. None of these species has ever been reported to display any sort of catalytic properties whatsoever.…”

Section: Tethered Ferrocene Catalystsmentioning

confidence: 99%

“…NMR and cyclic voltammetry studies showed that, in acid solution, protons (H + ) transiently bound the Fe atoms in 15a, with the two ferrocenes separately protonated at each Fe center [44][45][46]. The binding at each Fe center involved a dynamic equilibrium, which included direct Fe-H binding, as well as protonation at the ring carbons, as depicted in Scheme 10 [41,42].…”

Section: Tethered Ferrocene Catalystsmentioning

confidence: 99%

“…The rate of flexing of the tetra-metallocenes 19 and 20 (Scheme 11) also influenced their catalysis [42,44]. In 19, four ferrocenes are tethered in an arrangement that allows opposing Fe centers to alternately mediate collisions between attached hydrogen reactants during flexing at room temperature.…”

Section: Tethered Ferrocene Catalystsmentioning

confidence: 99%

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Kinematic molecular manufacturing machines

Boskovic

Balakrishnan

Huang

et al. 2016

Coordination Chemistry Reviews

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The principles of kinematic manufacturing machines of the type widely used since the industrial revolution are reviewed. Consideration is then given to how the principles of kinematics ('the geometry of motion') may manifest in molecular catalysts. Actions of this type involve synchronized, regular, repeated and rapid conformational flexing along geometrically optimum pathways that define a single degree of freedom. The proposition that many of the catalysts of biology, enzymes, may generally exploit a kinematic action is discussed. Thereafter, in the major portion of this work, representative abiological molecular catalysts whose actions display the characteristic features of kinematic manufacturing processes, are reviewed. In accordance with the principles of kinematics, molecular catalytic actions of this type are shown to be capable of transforming unremarkable chemical species into powerful catalysts with high activities, selectivities, and durabilities. Disciplines Engineering | Physical Sciences and Mathematics Engineering, Wenzhou University, Wenzhou 325027, Peoples Republic of ChinaAbstract: The principles of kinematic manufacturing machines of the type widely used since the industrial revolution are reviewed. Consideration is then given to how the principles of kinematics ('the geometry of motion') may manifest in molecular catalysts. Actions of this type involve synchronized, regular, repeated and rapid conformational flexing along geometrically optimum pathways that define a single degree of freedom. The proposition that many of the catalysts of biology, enzymes, may generally exploit a kinematic action is discussed. Thereafter, in the major portion of this work, representative abiological molecular catalysts whose actions display the characteristic features of kinematic manufacturing processes, are reviewed. In accordance with the principles of kinematics, molecular catalytic actions of this type are shown to be capable of transforming unremarkable chemical species into powerful catalysts with high activities, selectivities, and durabilities.

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