Substituent effects in cationic bis(arene)chromium compounds. Electronic and ESR spectra, and an x-ray structure of bis(1,3,5-triisopropylbenzene)chromium(I) iodide

Li, Tomi Ting Tung; Kung, Wei Jen; Ward, Donald L.; McCulloch, Beth; Brubaker, Carl H.

doi:10.1021/om00069a023

Cited by 15 publications

(7 citation statements)

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“…Therefore we assigned the signal to a [Cr(bis-arene)] ? type complex, which accounted for the 10 equivalent protons and was in analogy to the EPR spectra of previously reported Cr(I) bis-arene complexes [52,53]. Simulation of the low temperature anisotropic EPR spectrum revealed a reversed g tensor for this new signal ([Cr(bis-arene)] ?…”

Section: Chromium (I) Catalyzed Ethylene Oligomerisationsupporting

confidence: 68%

“…The resulting isotropic EPR spectrum (Fig. 3e) was simulated based on a g iso value of 1.988, with 10 equivalent protons ( 1 H: I = 1/2, H a iso = 9.65 MHz) and a weak 53 Cr hyperfine pattern (9.5 % abundance, I = 3/2, Cr a iso = 50.5 MHz) [51]. As an identical EPR spectrum was obtained following activation with trimethylaluminium (TMA), it was determined that coordinated ethyl or methyl fragments were not responsible for the hyperfine pattern observed.…”

Section: Chromium (I) Catalyzed Ethylene Oligomerisationmentioning

confidence: 99%

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The Role of Low Valent Transition Metal Complexes in Homogeneous Catalysis: An EPR Investigation

Carter

Murphy

2015

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Section: Chromium (I) Catalyzed Ethylene Oligomerisationsupporting

confidence: 68%

Section: Chromium (I) Catalyzed Ethylene Oligomerisationmentioning

confidence: 99%

The Role of Low Valent Transition Metal Complexes in Homogeneous Catalysis: An EPR Investigation

Carter

Murphy

2015

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“…Over time, disappearance of the absorption bands of 2 is observed and a strong CT band is observed. The CT band likely originates from 5 as bis(arene)Cr(I) complexes have been shown to have strong CT bands in a similar region . Due to the intense CT band, it cannot be concluded whether 3 is also being formed in toluene.…”

Section: Resultsmentioning

confidence: 99%

Spectroscopic Investigation of the Activation of a Chromium-Pyrrolyl Ethene Trimerization Catalyst

et al. 2018

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1-Hexene is an important α-olefin for polyethylene production and is produced from ethene. Recent developments in the α-olefin industry have led to the successful commercialization of ethene trimerization catalysts. An important industrially applied ethene trimerization system uses a mixture of chromium 2-ethylhexanoate, AlEt3, AlEt2Cl, and 2,5-dimethylpyrrole (DMP). Here, we have studied the activation of this system using catalytic and spectroscopic experiments (XAS, EPR, and UV–vis) under conditions employed in industry. First, chromium 2-ethylhexanoate was prepared and characterized to be [Cr3O(RCO2)6(H2O)3]Cl. Next, the activation of chromium 2-ethylhexanoate with AlEt3, AlEt2Cl, and DMP was studied, showing immediate reduction (<5 ms) of the trinuclear Cr(III) carboxylate and formation of a neutral polynuclear Cr(II) carboxylate complex. Over time, this Cr(II) carboxylate complex is partially converted into a chloro-bridged dinuclear Cr(II) pyrrolyl complex. In cyclohexane, small quantities of an unknown Cr(I) complex (∼1% after 1 h) are observed, while in toluene, the quantity of Cr(I) is much higher (∼23% after 1 h). This is due to the formation of cationic bis(tolyl)Cr(I) complexes, which likely leads to the observed inferior performance using toluene as the reaction solvent. Catalytic studies allow us to exclude some of the observed Cr(I) and Cr(II) complexes as the active species in this catalytic system. Using this combination of techniques, we have been able to structurally characterize complexes of this selective Cr-catalyzed trimerization system under conditions which are employed in industry.

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“…15 (A)). 26,28 At low temperatures (230 K) the hyperfine structure of the EPR signal can be observed. The very similar values of the superfine coupling constants, a 1 = 3.5 G and a 2 = 3.6 G, indicate the superposition of the signals corresponding to bis(arene)Cr + species with even and odd numbers of aromatic protons in the aromatic rings.…”

Section: The Preparation Of Non-linear Optical Compositions Based On ...mentioning

confidence: 99%

“…Indeed, it is known that bis(arene) complexes with bulky (or numerous) ring substitutents exhibit hyperfine line broadening because of hindered molecular rotation, and no hyperfine structure is observed. 28 Thus, a possible rationalization for the presense of Cr(+1) paramagnetic species giving broadened hyperfine lines even at low temperatures is the presence of bulky polymeric substituents in the benzene rings. It is interesting that the TCNE radical-anion signal is absent in the spectrum unlike for free (arene) 2 Cr + as described in the literature.…”

Section: The Preparation Of Non-linear Optical Compositions Based On ...mentioning

confidence: 99%

Chromium-containing organometallic nanomaterials for non-linear optics

Klapshina¹,

Grigoryev²,

Lopatina³

et al. 2006

New J. Chem.

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International audienceNovel nonlinear optical polymeric film-producing nanocomposites based on bis(arene)chromium complexes incorporated into a CN-containing matrix have been developed. Polymer-precursors were prepared by the reaction of Cr(EtnC6H6 n)2 (n = 1,2,3) with CN-containing vinyl monomers (acrylonitrile, crotononitrile or ethyl 2-cyanopropenoate). Extraordinarily high third-order nonlinear optical susceptibilities of the ultra-fast electronic type have been demonstrated at various wavelengths for polymer films prepared from these composites by using the Z-scan technique and the spectrally-resolved two-beam coupling method. A notable electro-optical response of the composite with an essential contribution of orientational effects was established. The electron-diffraction pattern in films and the presence of a non-zero electro-optical coefficient in the absence of an external poling field indicates the formation of self-organized structures. In CrPAN and [CrPAN]+TCNE–, a single Cr-C distance was found in the EXAFS data refinement, showing that the arene rings are parallel and symmetric as in bis(benzene)chromium. The Cr-C distances in these two materials are very similar to the 2.13 Angstroms in bis(benzene)chromium. In [CrPAN]+OH–, more than one metal-carbon distance was resolved, showing either that the two arene rings are at different distances from the metal, or that they are tilted rather than parallel

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Substituent effects in cationic bis(arene)chromium compounds. Electronic and ESR spectra, and an x-ray structure of bis(1,3,5-triisopropylbenzene)chromium(I) iodide

Cited by 15 publications

References 0 publications

The Role of Low Valent Transition Metal Complexes in Homogeneous Catalysis: An EPR Investigation

The Role of Low Valent Transition Metal Complexes in Homogeneous Catalysis: An EPR Investigation

Spectroscopic Investigation of the Activation of a Chromium-Pyrrolyl Ethene Trimerization Catalyst

Chromium-containing organometallic nanomaterials for non-linear optics

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