π-Olefin—iridium-komplexe XXIV photoreaktionen von [CpM(C2H4)2](M = Rh, Ir) mit Alkinen — Fundgrube für neue π-Komplexe

Müller, Jörn; Akhnoukh, Talaat; Gaede, Petra Escarpa; Ao-Ling, Guo; Moran, Paul H.; Qiao, Ke

doi:10.1016/s0022-328x(97)00063-6

Cited by 29 publications

(8 citation statements)

References 29 publications

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“…Such species are unknown experimentally. However, related metallacyclopentadiene rings are found in Fe, , Co, − Ni, − Ru, − Rh, , and Ir derivatives. Such metallacyclopentadiene derivatives include the metallametallocenes CpM(C 4 H 4 M′)Cp (M, M′ = Fe, Co, Ni) and dinickelametallocenes (η 5 -CpNiC 4 H 4 ) 2 M (M = Fe, Co, Ni) that have been the subjects of recent theoretical studies.…”

Section: Introductionmentioning

confidence: 99%

Metallocene versus Metallabenzene Isomers of Nickel, Palladium, and Platinum

et al. 2014

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The relative energies of singlet and triplet metallocene, metallabenzene, and metallacyclopentadiene C10H10M isomers (M = Ni, Pd, Pt) have been examined using density functional theory. For the C10H10Ni system, the experimentally known triplet nickelocene (η5-Cp)2Ni is the lowest energy isomer by ∼17 kcal/mol with respect to singlet nickelocene. For the C10H10Pd system, the triplet and singlet palladocene structures have similar energies within ∼2 kcal/mol. However, the singlet palladocene has a “slipped ring” (η3-Cp)2Pd structure with two trihapto Cp rings. The C10H10Pt system is different since the platinabenzene CpPtC5H5 isomer is the lowest energy structure. This is in accord with the synthesis of stable substituted CpPtC5H3R2 platinabenzenes by Haley and co-workers [ Haley M. M. Haley M. M. Organometallics2004231174]. However, the slipped ring singlet platinocene (η3-Cp)2Pt to the isomeric platinocene lies only ∼2 kcal/mol above the platinabenzene global minimum, so the energy barrier for conversion of the platinabenzene must be substantial. The following general observations can be made regarding the relative stabilities of isomeric C10H10M (M = Ni, Pd, Pt) structures: (1) Triplet structures become less favorable energetically than isomeric singlet structures in the sequence Ni < Pd < Pt. (2) Slipped metallocene structures with trihapto η3-Cp rather than pentahapto η5-Cp rings leading ultimately to 16- rather than 18-electron metal configurations become increasingly favorable energetically in the sequence Ni < Pd < Pt. (3) Metallabenzene (η5-Cp)MC5H5 structures with pentahapto Cp rings are always more favorable energetically than isomeric metallacyclopentadiene (η6-C6H6)MC4H4 structures with hexahapto benzene rings.

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Section: Introductionmentioning

confidence: 99%

Metallocene versus Metallabenzene Isomers of Nickel, Palladium, and Platinum

et al. 2014

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“…7 The rhodium complex and its analogues lose ethene readily under photochemical conditions, 8-13 but the half sandwich iridium ethene complexes are prone to photochemical isomerization to vinyl hydride complexes in addition to photodissociation of ethene. [14][15][16][17] Several studies have been carried out on the reactivity of [(g 5 -C 5 H 5 )Rh(C 2 H 4 ) 2 ] and [(g 5 -C 5 Me 5 )Rh(C 2 H 4 ) 2 ] towards silanes and species of the type [(g 5 -C 5 H 5 )Rh(SiR 3 )(H)(C 2 H 4 )] have been characterised following irradiation of [(g 5 -C 5 H 5 )Rh(C 2 H 4 ) 2 ]. 8,18-24 Much less is known about the reactivity of their cobalt analogues.…”

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confidence: 99%

Low temperature in situ UV irradiation of [(η⁵-C₅H₅)Co(C₂H₄)₂] in the NMR probe: formation of Co(iii) silyl hydride complexes

2007

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Low temperature in situ UV irradiation of [(eta(5)-C(5)H(5))Co(C(2)H(4))(2)] in the presence of silanes enables the characterisation of unstable fluxional Co(III) silyl hydride complexes [(eta(5)-C(5)H(5))Co(SiR(3))(H)(C(2)H(4))] (SiR(3) = SiEt(3), SiMe(3) or SiHEt(2)) by NMR spectroscopy; the reaction of [Co(eta(5)-C(5)H(5))(C(2)H(4))(2)] with HSiR(3) proceeds thermally to reach an equilibrium when SiR(3) = Si(OMe)(3) or SiClMePh.

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“…The fused five‐membered rings (5MRs) and the 3MR in Figure 2 are almost coplanar, which is reflected by particularly small dihedral angles (ranging from 0.012–0.2°). The metalcarbon bond lengths (i.e., MC1, MC4, and MC7) are all in the range of other metallaaromatics7 except 1‐Rh , in which the RhC7 bond length is 2.387 Å, which is much longer than that in the first‐reported aromatic rhodacyclopentadiene (1.983 Å) 28. The CC bond lengths in 1‐Tc (1.389–1.408 Å), 1‐Re (1.395–1.414 Å), and 1‐Os (1.378–1.401 Å) of the fused 5MRs are between single and double carboncarbon bond lengths, close to those in benzene (1.396 Å).…”

Section: Resultsmentioning

confidence: 82%

“…The metalÀcarbon bond lengths (i.e.,M ÀC1, MÀC4, and MÀC7) are all in the range of other metallaaromatics [7] except 1-Rh,i n which the RhÀC7 bond length is 2.387 , which is much longer than that in the first-reporteda romatic rhodacyclopentadiene (1.983 ). [28] The CÀCb ond lengths in 1-Tc (1.389-1.408 ), 1-Re (1.395-1.414), and 1-Os (1.378-1.401 ) of the fused 5MRs are between single and double carbonÀcarbon bond lengths, close to those in benzene (1.396 ). Thus, the fused 5MRs in class Ac ompounds are delocalized.…”

Section: Geometry Of the Cyclopropametallapentalenesmentioning

confidence: 87%

σ Aromaticity Dominates in the Unsaturated Three‐Membered Ring of Cyclopropametallapentalenes from Groups 7–9: A DFT Study

Hao

Zhu

2015

Chemistry A European J

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Aromaticity, an old but still fantastic topic, has long attracted considerable interest of chemists. Generally, π aromaticity is described by π-electron delocalization in closed circuits of unsaturated compounds whereas σ-electron delocalization in saturated rings leads to σ aromaticity. Interestingly, our recent study shows that σ aromaticity can be dominating in an unsaturated three-membered ring (3MR) of cyclopropaosmapentalene. An interesting question is raised: Can the σ aromaticity, which is dominant in the unsaturated 3MR, be extended to other cyclopropametallapentalenes? If so, how could the metal centers, ligands, and substituents affect the σ aromaticity? Here, we report a thorough theoretical study on these issues. The nucleus-independent chemical shift calculations and the anisotropy of the current-induced density plots reveal the dominant σ aromaticity in these unsaturated 3MRs. In addition, our calculations show that substituents on the 3MRs have significant effects on the σ aromaticity, whereas the ligand effect is particularly small.

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π-Olefin—iridium-komplexe XXIV photoreaktionen von [CpM(C2H4)2](M = Rh, Ir) mit Alkinen — Fundgrube für neue π-Komplexe

Cited by 29 publications

References 29 publications

Metallocene versus Metallabenzene Isomers of Nickel, Palladium, and Platinum

Metallocene versus Metallabenzene Isomers of Nickel, Palladium, and Platinum

Low temperature in situ UV irradiation of [(η⁵-C₅H₅)Co(C₂H₄)₂] in the NMR probe: formation of Co(iii) silyl hydride complexes

σ Aromaticity Dominates in the Unsaturated Three‐Membered Ring of Cyclopropametallapentalenes from Groups 7–9: A DFT Study

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π-Olefin—iridium-komplexe XXIV photoreaktionen von [CpM(C2H4)2](M = Rh, Ir) mit Alkinen — Fundgrube für neue π-Komplexe

Cited by 29 publications

References 29 publications

Metallocene versus Metallabenzene Isomers of Nickel, Palladium, and Platinum

Metallocene versus Metallabenzene Isomers of Nickel, Palladium, and Platinum

Low temperature in situ UV irradiation of [(η5-C5H5)Co(C2H4)2] in the NMR probe: formation of Co(iii) silyl hydride complexes

σ Aromaticity Dominates in the Unsaturated Three‐Membered Ring of Cyclopropametallapentalenes from Groups 7–9: A DFT Study

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Low temperature in situ UV irradiation of [(η⁵-C₅H₅)Co(C₂H₄)₂] in the NMR probe: formation of Co(iii) silyl hydride complexes