Über Aromatenkomplexe von Metallen, XXVI. IR‐Untersuchungen an Cyclopentadienyl‐Metall‐Komplexen

Fritz, Heinz P.

doi:10.1002/cber.19590920405

Cited by 79 publications

(11 citation statements)

References 10 publications

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“…[3,37] CAU-TION: Extreme care must be taken in dealing with beryllium compounds because they are very toxic and can cause serious irreversible effects.…”

Section: Methodsmentioning

confidence: 99%

“…[1] It was clear from the outset that [Cp 2 Be] did not possess a highly symmetric geometry (as ferrocene does) because of various measured properties, [2,3] including the dipole moment observed in solution. [1] A structure for the compound was first postulated by Almenningen and co-workers based upon data from vapour-phase electron diffraction.…”

Section: Introductionmentioning

confidence: 97%

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Structure and Dynamics of Homoleptic Beryllocenes: A Solid‐State ⁹Be and ¹³C NMR Study

Hung

Macdonald

Schurko

2004

Chemistry A European J

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The correlation between anisotropic 9Be NMR (quadrupolar and chemical shielding) interactions and the structure and dynamics in [Cp2Be], [Cp2*Be], and [(C5Me4H)2Be] is examined by solid-state 9Be NMR spectroscopy, as well as by ab initio and hybrid density functional theory calculations. The 9Be quadrupole coupling constants in the three compounds correspond well to the relative degrees of spherical ground-state electronic symmetry of the environment about beryllium. Theoretical computations of NMR interaction tensors are in excellent agreement with experimental values and aid in understanding the origins of NMR interaction tensors and their correlation to molecular symmetry. Variable-temperature (VT) 9Be and 13C NMR experiments reveal a highly fluxional structure in the condensed phase of [Cp2Be]. In particular, the pathway by which the Cp rings of [Cp2Be] 'invert' coordination modes is examined in detail using hybrid density functional theory in order to inspect variations of the 9Be NMR interaction tensors. The activation energy for the 'inversion' process is found to be 36.9 kJ mol(-1) from chemical exchange analysis of 13C VT CP/MAS NMR spectra. The low-temperature (ca. -100 degrees C) X-ray crystal structures of all three compounds have been collected and refined, and are in agreement with previously reported structures. In addition, the structure of the same Cp2Be crystal was determined at 20 degrees C and displays features consistent with increased intramolecular motion, supporting observations by 9Be VT NMR spectroscopy.

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“…[3,37] CAU-TION: Extreme care must be taken in dealing with beryllium compounds because they are very toxic and can cause serious irreversible effects.…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Structure and Dynamics of Homoleptic Beryllocenes: A Solid‐State ⁹Be and ¹³C NMR Study

Hung

Macdonald

Schurko

2004

Chemistry A European J

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“…Com base no espectro infravermelho do PFV foi possível verificar: a) a estereoquímica dos grupos vinilena por meio da presença de bandas de deformação angular fora do plano = C-H em 956 e em 859 cm -1 , que sugerem configuração trans e cis, respectivamente; b) a presença de grupos terminais C(=O)H, evidenciada por uma banda fraca em 1701 cm -1 ; e c) a presença dos anéis de ferroceno por meio de bandas de estiramento da ligação C-H em 3085 cm -1 , entre outras [37] . O espectro Raman permitiu confirmar a presença de duplas ligações com configuração trans e cis por meio de bandas características em 1309 e 1235 cm -1 , respectivamente [38] .…”

Section: Resultsunclassified

Síntese de poli(1,1'-ferrocenilenovinileno) via acoplamento de McMurry

Gonçalves

Kawano²,

Gruber

2008

Polímeros

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dispositivos eletroluminescentes [15] e, mais recentemente, com células solares [16] , transistores magnéticos [17][18][19] e narizes eletrônicos [20][21][22] . A combinação da eletroafinidade dos metais de transição com as propriedades eletrônicas dos polímeros conjugados é uma estratégia atrativa para gerar polímeros híbridos, combinando propriedades físicas, eletrônicas e magnéticas propícias para diversas aplicações. A delocalização eletrô-nica ao longo da cadeia polimérica pode, aumentar a comunicação entre os centros metálicos, permitindo um ajuste fino das propriedades magnéticas e espectroscópicas para aplicações específicas [23,24] . Usualmente, polímeros condutores contendo ferroceno na cadeia principal apresentam interessantes propriedades semicondutoras [25] e magnéticas [26] , além de foto-atividade [27] , desta forma é possível a obtenção de materiais nanoestruturados e nanoorganizados, com sí-tios redox ativos e características interessantes para aplicações em dispositivos ópticos, fotônicos e magnéticos [28,29] . Neste artigo, apresentam-se a síntese em uma úni-ca etapa, via reação de McMurry, e a caracterização de poli(1,1'-ferrocenilenovinileno) (1) (PFV), polímero análo-go ao PPV, que possui grupos 1,1'-ferrocenileno incorporados à sua cadeia principal (Figura 2). Cabe ressaltar que este polímero já foi descrito uma única vez na literatura [30] , IntroduçãoAtualmente, o interesse por polímeros conjugados organometálicos tem aumentado consideravelmente. Isso se deve sobretudo à diversidade de aplicações possíveis: em dispositivos fotovoltaicos [1] , diodos emissores de luz [2] , ímãs moleculares [3] , sensores de gases [4] , entre outras. Segundo a literatura, a incorporação de metalocenos a polímeros conjugados altera expressivamente a estrutura eletrônica destes [5] . Com 18 elétrons na camada de valência, o ferroceno é o membro mais estável da série dos metalocenos [6] , não sofrendo modificações por exposição à umidade ou ao ar. Pode ser oxidado reversivelmente por via eletroquímica ou pela ação de oxidantes fracos. O ferroceno pode ser considerado um areno rico em elétrons, possuindo reatividade mais acentuada do que a do benzeno. Em reações de Friedel-Crafts, por exemplo, sua reatividade pode alcançar 10 6 vezes a reatividade do benzeno [7] . Assim, inúmeros derivados podem ser preparados a partir do ferroceno, de modo a construir estruturas diversas com o emprego deste metaloceno (Figura 1) [8][9][10][11][12][13] . Entre as diversas classes de polímeros conjugados, a família dos poli(arilenovinileno)s (PAVs) [14] (Figura 2), cujo representante mais conhecido é o poli(p-fenilenovinileno) (1,1'-ferrocenilenovinileno Resumo: Com base nas grandes modificações das propriedades de materiais poliméricos resultantes da inclusão de unidades organometálicas, descrevem-se neste trabalho a síntese e a caracterização de um polímero organometálico conjugado com estrutura semelhante à de poli(p-fenilenovinileno) (PPV), o qual apresenta grupos 1,1'-ferrocenileno no lugar de 1,4-fenileno em sua cad...

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“…From theoretical considerations and physical chemical measurements, a number of workers (4,(8)(9)(10)(11)(12) have predicted that the ~legative charge on the cyclopentadiellyl anion will not be localized on a partic~ilar carboll atom but will be distributed over the…”

Section: Introductionmentioning

confidence: 99%

“…Pyridi~lium cyclopentadienylide has been described by Lloyd and Sneezum (5) and by Kosower and Ramsey (6). Triphenylphosphonium cyclopentadienylide has also been reported (7).From theoretical considerations and physical chemical measurements, a number of workers (4,(8)(9)(10)(11)(12) have predicted that the ~legative charge on the cyclopentadiellyl anion will not be localized on a partic~ilar carboll atom but will be distributed over theion as a whole, as depicted by I. In the present study, attempts were made to obtain, by the tracer technique, some direct experimental evidence ill support of these theoretical predictions.…”

mentioning

confidence: 99%

A STUDY ON THE STRUCTURE OF THE CYCLOPENTADIENYL ANION WITH C¹⁴ AS TRACER

Tkachuk¹,

Lee²

1959

Can. J. Chem.

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Starting with formaldehyde-C1" 1,2-dibromocyclopentane-4-C" ( X I ) was synthesized in eight steps. Conversion of X I to cyclopentadiene was accomplished in three different ways, namely: the dehydrobromination of X I with quinoline a t 195-198' C, the preparation of 1,2-bis-(trimethylammonium)-cyclopentane-4-14 hydroxide from X I followed by thermal decomposition, and the conversion of X I to 3,5-dibromocyclopentene followed by reaction of the latter with magnesium in d r y ether. Degradations of the samples of cyclopentadiene obtained by these three synthetic routes showed a completely randomized distribution of the Cld activity, with 20y0 of the total activity on each of the five carbon positions. These results led t o the conclusion that these preparations of cyclopentadieile very likely involved ionization to the cyclopentadienyl anion. T h e randomized distribution of C" in the resulting products thus furnishes a strong indication that all five carbon positions in the cyclopentadienyl anion are equivalent. INTRODUCTIONT h e acidity of cyclopentadiene was first recognized i11 1900 by Thiele (I), and its potassium salt was prepared in 1901 (2). This salt is stable, though very reactive. The reason for the stability of salts containing the cyclopentadienyl anion has been given asearly as 1928, by Goss and Ingold (3), and is that this ion has six (n) electrons, distributed over the entire five-membered ring, thus constituting a stable aromatic system similar to benzene. T h e resonance energy of this ion has been calculated to be about 42 kcal per mole (4).Salts of cyclopentadiene with organic cations are also known. Pyridi~lium cyclopentadienylide has been described by Lloyd and Sneezum (5) and by Kosower and Ramsey (6). Triphenylphosphonium cyclopentadienylide has also been reported (7).From theoretical considerations and physical chemical measurements, a number of workers (4,(8)(9)(10)(11)(12) have predicted that the ~legative charge on the cyclopentadiellyl anion will not be localized on a partic~ilar carboll atom but will be distributed over theion as a whole, as depicted by I. In the present study, attempts were made to obtain, by the tracer technique, some direct experimental evidence ill support of these theoretical predictions.If it were possible to synthesize cyclopentadiene-5-C14 (11), conversion of this conlpound to its potassi~~m salt followed by regeneration should yield a cyclopentadiene in which the C14 distribution could provide definitive evidence for the struct~ire of the cyclopentadienyl anion. Should the anion have the symmetrical electronic structure I, on 'Manuscript

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Über Aromatenkomplexe von Metallen, XXVI. IR‐Untersuchungen an Cyclopentadienyl‐Metall‐Komplexen

Cited by 79 publications

References 10 publications

Structure and Dynamics of Homoleptic Beryllocenes: A Solid‐State ⁹Be and ¹³C NMR Study

Structure and Dynamics of Homoleptic Beryllocenes: A Solid‐State ⁹Be and ¹³C NMR Study

Síntese de poli(1,1'-ferrocenilenovinileno) via acoplamento de McMurry

A STUDY ON THE STRUCTURE OF THE CYCLOPENTADIENYL ANION WITH C¹⁴ AS TRACER

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Über Aromatenkomplexe von Metallen, XXVI. IR‐Untersuchungen an Cyclopentadienyl‐Metall‐Komplexen

Cited by 79 publications

References 10 publications

Structure and Dynamics of Homoleptic Beryllocenes: A Solid‐State 9Be and 13C NMR Study

Structure and Dynamics of Homoleptic Beryllocenes: A Solid‐State 9Be and 13C NMR Study

Síntese de poli(1,1'-ferrocenilenovinileno) via acoplamento de McMurry

A STUDY ON THE STRUCTURE OF THE CYCLOPENTADIENYL ANION WITH C14 AS TRACER

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Structure and Dynamics of Homoleptic Beryllocenes: A Solid‐State ⁹Be and ¹³C NMR Study

Structure and Dynamics of Homoleptic Beryllocenes: A Solid‐State ⁹Be and ¹³C NMR Study

A STUDY ON THE STRUCTURE OF THE CYCLOPENTADIENYL ANION WITH C¹⁴ AS TRACER