[1.1]Ferrocenophanes in solution—Anti or syn isomers?

Karlsson, Annika C.; Löwendahl, Martin; Hilmersson, Görgan; Davidsson, Öjvind; Ahlberg, Per

doi:10.1002/(sici)1099-1395(199606)9:6<436::aid-poc801>3.3.co;2-m

Cited by 4 publications

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“…Recently it was discovered that [1.1]ferrocenophanes such as 7 with anti -structures may exist . Previously only syn -structures were assumed to be energetically possible. , The experimental results gathered so far do not distinguish syn- forms ( 1c and 1d ) from anti- forms ( 1e and 1f ) with the Li in exo- or endo -positions.…”

Section: Resultsmentioning

confidence: 99%

Structure of [1.1]Ferrocenophanyllithium in the Solution and the Solid State. Absence of an Intramolecular [C−H−C]^- Hydrogen Bond

et al. 1997

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[1.1]Ferrocenophanyllithium (1) is shown by dynamic NMR (DNMR) and isotopic perturbation to undergo a rapid intramolecular 1,12-proton transfer coupled with 1,12-lithium ion transfer. The first [C−H−C]- hydrogen bond previously reported to be present in 1 is shown by X-ray crystallography to be absent in the solid state. The 13C NMR spectrum of the bridge-labeled compound [1,12-13C2][1.1]ferrocenophanyl[1-6Li]lithium (6) in 2,5-dimethyltetrahydrofuran (DMTHF) displays a 1:1:1 triplet (1 J(13C,6Li) = 4.0 Hz) showing that 6Li is bonded to C-1 and that 1 is monomeric. Transient nuclear Overhauser effects (tNOE's) measured in DEE-d 10 in bridged monodeuterated 1 show that the bridges in 1 are syn and not anti to each other and that lithium is exo-coordinated to the anionic bridge carbon. The 1 J(13C,1H) coupling constants show that the hybridization of the carbanionic carbon is intermediate between sp2 and sp3. Thus the solution and solid state structures of 1 are similar. UV−vis spectroscopy shows that 1 exists mainly as contact ion pairs (CIPs) in the temperature range −100 to +25 °C in THF, DMTHF, and diethyl ether (DEE). In dimethoxyethane (DME), 1 is mainly CIPs above +25 °C but is mainly separated ion pairs (SIPs) below −30 °C.

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Section: Resultsmentioning

confidence: 99%

Structure of [1.1]Ferrocenophanyllithium in the Solution and the Solid State. Absence of an Intramolecular [C−H−C]^- Hydrogen Bond

et al. 1997

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“…When this isomerization process was monitored with 31 P NMR, the activation barrier was estimated to be ∆G 350 q ) 26.2 ( 0.6 kcal mol -1 . Since the macrocycle frameworks of 3a,b are both considered to be sufficiently flexible, like the related macrocycles (-CH 2 C 5 H 4 FeC 5 H 4 -) n (n ) 2, 3), [56][57][58][59] it is the inversion barrier of the phosphorus center itself that is mainly responsible for the present barrier of ca. 26 kcal mol -1 ; the flexible but bulky ferrocene backbones seem to make no practical steric contribution to the isomerization barrier.…”

Section: Resultsmentioning

confidence: 99%

Structure and Properties of the Macrocyclic Tridentate Ferrocenylphosphine Ligand (−PhPC₅H₄FeC₅H₄−)₃

et al. 2008

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Isolation and characterization were carried out for a novel tridentate ferrocenylphosphine macrocycle, (−PhPC5H4FeC5H4−)3, as follows. A photolytic ring-opening reaction of PPh-bridged [1]ferrocenophane in ether gave a mixture of its oligomers. After their sulfurization, GPC separation of low-molecular-weight species afforded two isomers of a macrocyclic trimer, 1,1′′:1′,1′′′′:1′′′,1′′′′′-tris(phenylthiophosphinidene)tris(ferrocene), in which three 1,1′-ferrocenediyl units and three P(S)Ph groups were alternately linked to form a macrocyclic ring. Although yields of both isomers were low (17% in total), they were successfully desulfurized in good yields without configurational inversion at their phosphorus centers by treatment with MeOTf/P(NMe2)3 (OTf = CF3SO3), to give the respective tridentate macrocyclic phosphine ligands. The molecular structure of one isomer (C 3 isomer) with C 3 symmetry was determined by X-ray analysis, while the other was identified as the C s isomer on the basis of 1H, 13C, and 31P NMR data. When the C 3 isomer was heated in toluene at around 80 °C, it isomerized gradually but almost completely to the C s isomer with the activation energy ΔG 350 ⧧ = 26.2 ± 0.6 kcal mol−1. The reaction of AgOTf with the C 3 isomer in CH2Cl2 gave a mononuclear silver complex in which the C 3 isomer encircled the Ag+ ion as a tridentate ligand. To our surprise, a similar reaction using the C s isomer gave the same silver complex as above, indicating that a facile conversion of the C s isomer to the C 3 isomer took place upon coordination to the Ag+ ion at room temperature.

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“…Moreover, the short C(Cp)-bridge distance of 1.797 Å also contributes to their short H(C5)‚‚‚H(C10*) separation of 1.82 Å, which suggests a substantial steric repulsion present between them. 4, [22][23][24] On the other hand, syn-2 adopts a wider twist angle of 24.81(7)°and therefore has a longer R-H‚‚‚R-H distance of 2.05 Å, leading in turn to a smaller H‚‚‚H repulsion than that of anti-2. In addition, the steric repulsion between the two PPh bridging groups is expected to be small in syn-2 because their endopositions are occupied with lone pairs (see Figure 5), the bulkiness of which is negligible from a stereochemical point of view, though with a slight electrostatic repulsion being anticipated between the lone pairs.…”

Section: Resultsmentioning

confidence: 99%

Phosphorus-Bridged [1.1]Ferrocenophane with syn and anti Conformations

Mizuta¹,

Imamura²,

Miyoshi³

et al. 2005

Organometallics

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Photolysis of PPh-bridged [1]ferrocenophane (1) in THF gave PPh-bridged [1.1]ferrocenophane (2) as a minor dimer along with major polymeric products. After subsequent sulfurization of the reaction mixture with elemental sulfur, both syn and anti isomers of P(S)Ph-bridged [1.1]ferrocenophane (3) were successfully isolated and characterized by X-ray analysis. syn-3 thus obtained was desulfurized stereoretentively to syn-2 with Si 2 Cl 6 in refluxing benzene, while anti-3 primarily gave the isomerized product, syn-2. Stereoretentive desulfurization of anti-3 to anti-2 was achieved with CF 3 SO 3 Me/P(NMe 2 ) 3 at room temperature. anti-2 thus obtained could be converted almost completely to syn-2 upon simple heating in toluene, indicative of the thermal instability of the anti isomer over the syn isomer. The yield of syn-2 was improved from 9% to 32% when THF used in the photolysis was replaced with ether and the reaction mixture was heated so as to isomerize anti-2, which had been formed concomitantly. A potential utility of syn-2 as a ligand was demonstrated by the formation of [CoCl 2 (syn-2)] (5) through a reaction of syn-2 with CoCl 2 .

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[1.1]Ferrocenophanes in solution—Anti or syn isomers?

Cited by 4 publications

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Structure of [1.1]Ferrocenophanyllithium in the Solution and the Solid State. Absence of an Intramolecular [C−H−C]^- Hydrogen Bond

Structure of [1.1]Ferrocenophanyllithium in the Solution and the Solid State. Absence of an Intramolecular [C−H−C]^- Hydrogen Bond

Structure and Properties of the Macrocyclic Tridentate Ferrocenylphosphine Ligand (−PhPC₅H₄FeC₅H₄−)₃

Phosphorus-Bridged [1.1]Ferrocenophane with syn and anti Conformations

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[1.1]Ferrocenophanes in solution—Anti or syn isomers?

Cited by 4 publications

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Structure of [1.1]Ferrocenophanyllithium in the Solution and the Solid State. Absence of an Intramolecular [C−H−C]- Hydrogen Bond

Structure of [1.1]Ferrocenophanyllithium in the Solution and the Solid State. Absence of an Intramolecular [C−H−C]- Hydrogen Bond

Structure and Properties of the Macrocyclic Tridentate Ferrocenylphosphine Ligand (−PhPC5H4FeC5H4−)3

Phosphorus-Bridged [1.1]Ferrocenophane with syn and anti Conformations

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Structure of [1.1]Ferrocenophanyllithium in the Solution and the Solid State. Absence of an Intramolecular [C−H−C]^- Hydrogen Bond

Structure of [1.1]Ferrocenophanyllithium in the Solution and the Solid State. Absence of an Intramolecular [C−H−C]^- Hydrogen Bond

Structure and Properties of the Macrocyclic Tridentate Ferrocenylphosphine Ligand (−PhPC₅H₄FeC₅H₄−)₃