Metal-.pi. complexes of benzene derivatives. 23. The radical anion of bis(.eta.6-benzene)chromium

Elschenbroich, Christoph; Bilger, Edgar; Koch, Juergen; Weber, Jacques

doi:10.1021/ja00327a056

Cited by 36 publications

(18 citation statements)

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“…This result is at variance with our previous calculation (6) which concluded to the opposite ordering for the 4elg and 3e2, MOs, and therefore to a LUMO with predominant metal character. The result 3e2, 5 4elg is, however, that deduced for the anion 1-from both a detailed analysis of the esr spectrum and SCF MS X a calculations (18). For the neutral system 1 this question is of minor importance since: ( i ) the energy difference between 3e2, and 4el, is very small and ( i i )…”

Section: Methodsmentioning

confidence: 75%

The electronic structures of bis(η⁶-benzene)- and bis(η⁶-naphthalene)chromium(0)

Weber¹,

Kündig²,

Goursot³

et al. 1985

Can. J. Chem.

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. SCF MS X a molecular orbital calculations are reported for the bis(q"benzene)-and bis(q6-naphthalene)chromium (O) complexes. The bonding may be essentially discussed in terms of the covalent interactions between the metal 3d and ligand .rr and .rr* orbitals. The different charges on chromium atom in the two systems are explained by the different balances between ligand-to-metal (bonding) and metal-to-ligand (back-bonding) electron donations. Some resemblances are found between the electronic structures of the two compounds and it is possible to correlate to a large extent the energy levels of their molecular orbitals. However, a shift towards lower values is predicted for the energy levels of the naphthalene complex, together with a large disruption of all the virtual .rr* and 3d* levels. This would undoubtedly favor nucleophilic attack followed by metal-ring or carbon-carbon bond cleavage, in agreement with the extreme lability of the coordinated arene rings observed in this complex.JACQUES WEBER, E. PETER KUNDIG, ANNICK GOURSOT et EDOUARD PENIGAULT. Can. J. Chem. 63, 1734Chem. 63, (1985.On a effectuC des calculs d'orbitales molCculaires MS Xa en champ autocohCrent pour les complexes bis(q"benzkne)-et bis(q6-naphtal&ne)chrome(0). On peut decrire la liaison dans le complex presque essentiellement l'aide des interactions covalentes entre les orbitales 3d du metal et les orbitales T et T* du ligand. On explique les diffkrentes charges sur l'atome de chrome dans les deux systemes par des bilans differents entre la donation directe d'klectrons ligand-mCtal et la rCtrodonation mCtal-ligand. Toutefois, on prCdit un dkplacement vers des valeurs plus basses pour les niveaux CnergCtiques du complexe de naphtalene ainsi qu'un mClange important de tous les niveaux virtuels .rr* et 3d*. Ceci devrait de toute evidence favoriser une attaque nuclCophile, suivie d'une rupture de la liaison mCtal-cycle ou carbone-carbone, en accord avec la labilitC extrCme observke dans ces complexes pour les cycles areniques coordonnCs.[Traduit par le journal]

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Section: Methodsmentioning

confidence: 75%

The electronic structures of bis(η⁶-benzene)- and bis(η⁶-naphthalene)chromium(0)

Weber¹,

Kündig²,

Goursot³

et al. 1985

Can. J. Chem.

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“…This fast exchange rules out a mechanism in which the triscyclohexyl phosphines undergo rotation around the Rh-P bonds, as this has been shown to be a high energy process 2+ and [Cr(h-C 6 H 6 ) 2 ] with the radical cluster cation generated in situ. 7 In light of these new data that show there is no EPR signal at room temperature we now interpret this original spectrum as actually being due to trace amounts of [Cr(h-C 6 H 6 ) 2 ] + , 41 formed as the co-product of reduction. Indeed reduction in situ so that [Cr(h-C 6 H 6 ) 2 ] + was present gave in solution a strong 13-line spectrum with an isotropic g-value (g~2.01) identical to that previously reported.…”

Section: Solution Nmr and Esi-ms Characterisationmentioning

confidence: 85%

Using EPR to follow reversible dihydrogen addition to paramagnetic clusters of high hydride count: [Rh₆(PCy₃)₆H₁₂]⁺and [Rh₆(PCy₃)₆H₁₄]⁺

et al. 2010

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A combined structural/EPR/computational chemistry investigation is reported on the two paramagnetic hydrido-cluster salts [Rh 6 4 ] EPR measurements indicate two isomers, the proportion of which change with temperature and deuteration-one axial isomer and one rhombic isomer. DFT calculations on a number of plausible isomers give EPR parameters which fit the experimentally determined rhombic isomer to one in which there is an interstitial hydride in the cluster and thirteen hydride ligands on the surface, while the axial isomer has two dihydrogen-like ligands on the cluster surface. That these isomers lie close in energy comes from both the EPR measurements (as measured from equilibrium constants over a variable temperature range) and DFT calculations. Deuteration of the hydrides should favour the isomer with the lowest zero-point energy and this is the case, with the axial isomer (two D 2 ligands on the surface) being favoured over the rhombic.

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“…•+ (g = 1.986) 95 and C 60 •-(g = 2.000-1.996). 39 This is evidence of an exchange interaction between the spins of the Cr I (C 6 H 6 ) 2…”

Section: Methodsmentioning

confidence: 99%

“…95 Consequently, both coordinatively bound (Co II TPP•C 60 -) anions in complex 13 are diamagnetic and are not observed in the ESR spectrum. 95 Consequently, both coordinatively bound (Co II TPP•C 60 -) anions in complex 13 are diamagnetic and are not observed in the ESR spectrum.…”

Section: Coordination Of Fullerene Radical Anions Tomentioning

confidence: 97%

Ionic fullerene compounds containing negatively charged dimers and coordinatively bound anions

2007

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The review summarizes the results of investigations of ionic fullerene compounds contain ing negatively charged dimers and fullerene anions coordinated to metalloporphyrins. Fullerene radical anions were found to form diamagnetic singly bonded (C 60 -) 2 and (C 70 -) 2 dimers. Dimerization is reversible and leads to paramagnetic-diamagnetic phase transitions or a decrease in the magnetic moment of the complexes. The temperature, at which dissociation of the (C 60 -) 2 dimers begins, varies from 140 to 320 K; the corresponding temperature for the (C 70 -) 2 dimers varies from 260 to 360 K and higher. We prepared the first doubly bonded (C 60 -) 2 dimer. At 300 K, this dimer exists as a biradical. The fullerene radical anions form Co-C coordination bonds with cobalt(II) porphyrinates. The resulting anions are diamag netic. In some cases, Co-C coordination bonds undergo reversible dissociation, resulting in magnetic transitions from the diamagnetic to the paramagnetic state.

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Metal-.pi. complexes of benzene derivatives. 23. The radical anion of bis(.eta.6-benzene)chromium

Cited by 36 publications

References 1 publication

The electronic structures of bis(η⁶-benzene)- and bis(η⁶-naphthalene)chromium(0)

The electronic structures of bis(η⁶-benzene)- and bis(η⁶-naphthalene)chromium(0)

Using EPR to follow reversible dihydrogen addition to paramagnetic clusters of high hydride count: [Rh₆(PCy₃)₆H₁₂]⁺and [Rh₆(PCy₃)₆H₁₄]⁺

Ionic fullerene compounds containing negatively charged dimers and coordinatively bound anions

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Metal-.pi. complexes of benzene derivatives. 23. The radical anion of bis(.eta.6-benzene)chromium

Cited by 36 publications

References 1 publication

The electronic structures of bis(η6-benzene)- and bis(η6-naphthalene)chromium(0)

The electronic structures of bis(η6-benzene)- and bis(η6-naphthalene)chromium(0)

Using EPR to follow reversible dihydrogen addition to paramagnetic clusters of high hydride count: [Rh6(PCy3)6H12]+and [Rh6(PCy3)6H14]+

Ionic fullerene compounds containing negatively charged dimers and coordinatively bound anions

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The electronic structures of bis(η⁶-benzene)- and bis(η⁶-naphthalene)chromium(0)

The electronic structures of bis(η⁶-benzene)- and bis(η⁶-naphthalene)chromium(0)

Using EPR to follow reversible dihydrogen addition to paramagnetic clusters of high hydride count: [Rh₆(PCy₃)₆H₁₂]⁺and [Rh₆(PCy₃)₆H₁₄]⁺