An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
The reaction of NaC5H5 (NaCp) and hexafluorobenzene (1:1 ratio) in THF at 25 °C for 15 h afforded, after hydrolysis, a mixture of regioisomeric (pentafluorophenyl)cyclopentadienes. This mixture was isolated as a monoisomeric dimer of 1-(pentafluorophenyl)cyclopentadiene. The structure of the dimer was determined crystallographically. Flash vacuum thermolytic cracking of the dimer at 200 °C regenerated (pentafluorophenyl)cyclopentadiene as a mixture of regioisomers. In contrast, the reaction of NaCp, NaH, and C6F6 (1:2:5 ratio) in THF at reflux for 3 d affords, after hydrolysis, 1,4-bis(pentafluorophenyl)cyclopentadiene, which does not dimerize. Either the mono- or the disubsubstituted diene reacts with NaH in THF to afford the corresponding stable substituted sodium cyclopentadienides in high yields. Sodium (pentafluorophenyl)cyclopentadienide, (C6F5)C5H4Na, reacted with FeBr2, Re(CO)5Br, and ZrCl4(THF)2, to afford the transition metal complexes (η5-C5H4C6F5)2Fe, (η5-C5H4C6F5)Re(CO)3, and (η5-C5H4C6F5)2ZrCl2. Sodium 1,3-bis(pentafluorophenyl)cyclopentadienide reacted with FeBr2 and Re(CO)5Br to give the corresponding complexes [η5-1,3-C5H3(C6F5)2]2Fe and [η5-1,3-C5H3(C6F5)2]Re(CO)3. Infrared spectroscopic analysis of the tricarbonylrhenium(I) complexes and cyclic voltammetric analysis of the substituted ferrocenes quantified the strong electron-withdrawing effects of the pentafluorophenyl substituents.
Pentafluorophenyl-substituted cyclopentadienide anions are useful ligands for transition metals because the C6F5 substituent is not only highly electron withdrawing but also relatively stable. This chapter presents the synthesis of the monoarylated cyclopentadiene C5H5C6F5 on a useful but manageable scale (50mmol). The sequence begins with a nucleophilic substitution of cyclopentadienide for one fluorine substituent in hexafluorobenzene. Sodium hydride traps the product diene as the corresponding sodium salt Na(C5H4C6F5) in situ so that the diene can neither dimerize nor transfer its acidic proton to unreacted cyclopentadienyl anion. The resulting arylcyclopentadienyl anion (and the excess sodium hydride) is subsequently hydrolyzed in a cold aqueous workup. The resulting diene C5H5C6F5 is not thermally stable, but is easily converted back to the corresponding sodium salt. The procedure uses convenient, commercially available reagents, and product workup has been optimized.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
The metallocenes (C6F5C5H4)CpZrMe2 (1, Cp = C5H5) and (C6F5C5H4)2MMe2 (2a, M = Zr; 2b, M = Hf) were treated with B(C6F5)3 and, separately, with commercial methylalumoxane (MAO, depleted of excess Me3Al). The ensuing methide transfer reactions were followed by 19F NMR. Spectra of the "activated" species obtained using MAO and excess B(C6F5)3 were strikingly similar, suggesting that similar "cation-like" species are formed using either organo-Lewis acid, and the MAO-activated species were tentatively formulated as (C6F5C5H4)CpZrMe+ Me[AlMeO]n- and as (C6F5C5H4)2MMe+ Me[AlMeO]n- (M = Zr, Hf). The relative amount of L2MMe2 and [L2MMe]+ species observed in solution was measured as a function of [MAO] and as a function of [M] at constant [MAO]. Results are interpreted in terms of a canonical model in which MAO contains relatively few highly active Lewis acidic sites.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTricarbonyl(.eta.6-hexachlorobenzene)chromium(0)Paul G. Gassman and Paul A. DeckCite this: Organometallics 1994, 13, 5, 1934–1939Publication Date (Print):May 1, 1994Publication History Published online1 May 2002Published inissue 1 May 1994https://pubs.acs.org/doi/10.1021/om00017a058https://doi.org/10.1021/om00017a058research-articleACS PublicationsRequest reuse permissionsArticle Views383Altmetric-Citations23LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts
1,1'-Dilithioferrocene, or (CpLi)2Fe (1), reacts with excess C6F6 in THF to afford mostly (C6F5Cp)2Fe (2), accompanied by the diiron complex (C6F5Cp)FeCp(1,4-C6F4)CpFe(CpC6F5) (3). The reaction of 1 with 1.0 equiv of C6F6 affords a mixture of sparingly soluble step-growth oligomers assigned to [−FeCp(1,4-C6F4)−]n (4). [1-Li-2-RNCp]FeCp (6, RN = CH2NMe2) reacts with 1 equiv of C6F6 to afford [1-(C6F5)-2-RNCp]FeCp (7). Complex 6 reacts with 0.5 equiv of C6F6 to afford CpFe[2-RNCp](1,4-C6F4)[2-RNCp]FeCp as a mixture of two diastereomers (meso-8, major and dl-8, minor). The relative stereochemistry of meso-8 is established by crystallographic analysis of the corresponding bis(methiodide) (12). [1-Li-2-RNCp]Fe(CpLi) (9) reacts with excess C6F6 to afford mainly the diarylated ferrocene [1-(C6F5)-2-RNCp]Fe(CpC6F5) (10). The reaction of 9 instead with 1.0 equiv of C6F6 affords a mixture of oligomeric species assigned to the formula [−(2-RNCp)FeCp(1,4-C6F4)−]n (11). In contrast to 4, 11 is sufficiently soluble for characterization by solution NMR spectroscopy (end group analysis), and under optimized conditions a number-averaged degree of oligomerization corresponding to a linear Fe9 species is determined. The complexes 3, 7, 10, and 12 are characterized by single-crystal X-ray diffraction. Crystalline 3 exhibits infinite π-stacking interactions composed of intramolecular "triple-decker" C6F5−C6F4−C6F5 stacking and intermolecular Cp−C6F5 stacking. The crystal structure of 10 also shows intramolecular arene stacking, but intermolecular Cp−C6F5 interaction is interrupted by the dimethylaminomethyl substituent. None of these complexes show intermolecular stacking among the various C6F5 and C6F4 groups. Extensive intermolecular C−H···F−C interactions in the crystallographic packing diagrams of 3, 7, 10, 12, and CpFeCpC6F4C6F4CpFeCp (13) are characterized as either "purposeful" or "diffuse" by examining correlations of their respective H···F distances and C−H···F angles. Solution voltammetry of 3 shows two unresolved, reversible FeII|FeIII couples, suggesting weak electronic communication between the two iron centers despite the fully conjugated structure.
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