Structure of transition states in organic reactions. General theory and an application to the cyclobutene-butadiene isomerization using a semiempirical molecular orbital method

McIver, James; Komornicki, Andrew

doi:10.1021/ja00763a011

Cited by 827 publications

(333 citation statements)

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“…As expected, this effect is also seen in the A 1 '' CO stretching frequency which decreases as electron density donation from the heteroatom increases [12]. Due to the relative insensitivity of the carbonyl stretching frequencies toward the changes on the carbene substituents [13], little difference is observed in the measured IR frequencies for this series of complexes.…”

Section: Synthesis and Spectroscopic Characterizationsupporting

confidence: 66%

(Spectro)electrochemical investigations on (ferrocenyl)thiophenes modified by tungsten Fischer carbenes

Westhuizen¹,

Speck²,

Korb³

et al. 2014

Journal of Organometallic Chemistry

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A series of thiophene tungsten Fischer carbene complexes of type [(CO) 5 W=C(OMe)R] (1, R = 2-Th; 3, R = fcthFc) and [(CO) 5 W=C(OMe)-R'-(OMe)C=W(CO) 5 ] (2, R' = th; 5, R' = fcthfc) was synthesized for investigating low energy charge transfer interactions between the carbene substituents and the transition metal carbonyl fragment incorporating the thiophene heterocyclic system (Th = Thienyl; th = 2,5-thiendiyl; Fc = ferrocenyl; fc = 1,1'-ferrocenediyl).Electrochemical investigations were carried out on these complexes to get a closer insight into the electronic properties of 1, 2, 4 and 5. They reveal reversible one-electron redox events for the 2 ferrocenyl moieties. Moreover, typical electrode reactions could be found for the carbene reductions itself and for the tungsten carbonyl oxidation processes. However, for the thiophene complex 2 two well-separated one-electron reduction events were observed. During the UV-Vis-NIR spectroelectrochemical investigations typical low energy absorptions for the mixed-valent α,α'-diferrocenyl thiophene increment were found, as well as high energy NIR absorptions, which were attributed to metal-metal charge transfer transition between the tungsten carbonyl increment and the ferrocenyl units in the corresponding species. Further infrared spectroelectrochemical studies reveal that the electronic interactions in the corresponding cationic species can be described with weakly coupled class II systems according to Robin and Day.

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Section: Synthesis and Spectroscopic Characterizationsupporting

confidence: 66%

(Spectro)electrochemical investigations on (ferrocenyl)thiophenes modified by tungsten Fischer carbenes

Westhuizen¹,

Speck²,

Korb³

et al. 2014

Journal of Organometallic Chemistry

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“…Algorithms to locate transition states can generally be divided into single-ended approaches, which simply require a single starting geometry [11,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55], and double-ended methods, which are usually designed to find a transition state between two endpoints [10,56,57,58,59,60,61,62,…”

Section: Introductionmentioning

confidence: 99%

A doubly nudged elastic band method for finding transition states

Trygubenko¹,

Wales²

2004

The Journal of Chemical Physics

377

237

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A modification of the nudged elastic band (NEB) method is presented that enables stable optimisations to be run using both the limited-memory quasi-Newton (L-BFGS) and slow-response quenched velocity Verlet (SQVV) minimisers. The performance of this new 'doubly nudged' DNEB method is analysed in conjunction with both minimisers and compared with previous NEB formulations. We find that the fastest DNEB approach (DNEB/L-BFGS) can be quicker by up to two orders of magnitude. Applications to permutational rearrangements of the seven-atom Lennard-Jones cluster (LJ 7 ) and highly cooperative rearrangements of LJ 38 and LJ 75 are presented. We also outline an updated algorithm for constructing complicated multi-step pathways using successive DNEB runs. *

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“…28 In the case of 3, the IR spectrum measured shows the lifting of the degeneracy of the E-band that appears as two separate signals. In 2, overlapping of the signals associated with the A′ 1 and the E-modes occur.…”

Section: Synthesismentioning

confidence: 94%

Electrochemical illumination of thienyl and ferrocenyl chromium(0) Fischer carbene complexes

et al. 2013

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A series of ferrocenyl and thienyl mono-and biscarbene chromium(0) complexes 1-6 were synthesised.The complexes were characterised both spectroscopically and electrochemically, and the single crystal X-ray structure of 3 was determined. Electrochemical measurements in CH 2 Cl 2 revealed that the carbene double bond of 1-6 is reduced to an anion radical, − Cr-C˙at formal reduction potentials <−1.7 V vs.FcH/FcH + . A computational study on 1, 3 and 4 (B3LYP/def2-SVP level) is consistent with electrochemical results in showing that electrochemically generated chromium(I) species may be further electrochemically irreversibly oxidised to chromium(II) at E pa > 0.95 V. The reactivity towards follow-up chemical reactions of the anodically produced Cr(II) species is much higher than the reactivity of the cathodically produced radical anions as the latter was still observably reoxidised to the parent CrvC species at fast scan rates. The ferrocenyl group is oxidised electrochemically reversibly to ferrocenium at larger potentials than the electrochemically reversible oxidation of the Cr(0) centre to Cr(I). That all redox centres in 1-6 are involved in one-electron transfer steps was confirmed by comparing the ferrocenyl voltammetric wave with those of the other redox centres in linear sweep voltammetric experiments. The ferrocenyl group was electrochemically shown to stabilise the CrvC centre almost as much as the NHBu, and much more than the ethoxy and thienyl groups.

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Structure of transition states in organic reactions. General theory and an application to the cyclobutene-butadiene isomerization using a semiempirical molecular orbital method

Cited by 827 publications

References 1 publication

(Spectro)electrochemical investigations on (ferrocenyl)thiophenes modified by tungsten Fischer carbenes

(Spectro)electrochemical investigations on (ferrocenyl)thiophenes modified by tungsten Fischer carbenes

A doubly nudged elastic band method for finding transition states

Electrochemical illumination of thienyl and ferrocenyl chromium(0) Fischer carbene complexes

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