A cyclopentadienyl complex is a metal complex with one or more cyclopentadienyl groups (C 5 H 5-, abbreviated as Cp-).Based on the type of bonding between the metals and the cyclopentadienyl moieties, cyclopentadienyl complexes are classified into the following three categories: a) π-complexes, b) σ-complexes, and c) ionic complexes. Cyclopentadienyl ligands almost invariably bind to metals as a pentahapto (η -) bonding mode. Ferrocenium reagents are oxidants. When only a single Cp ligand is installed, the other ligands typically carbonyl, halogen, alkyl, and hydride. When the Cp rings are mutually parallel the compound is known as a sandwich complex. Bent metallocenes are represented by compounds of the type [MCp2Lx]. 2007; 127(3):034303 (ISSN: 0021-9606) Wörner HJ; Merkt F Still rarer, the Cp unit can bond to the metal via a three-carbons. Molekül‐ und Elektronenstruktur, Cyclic aryleneazachalcogens: Synthesis, vibrational spectra, and π-electron structures, Theoretical Aspects and Quantum Mechanical Calculations of Silaaromatic Compounds, Polymethinfarbstoffe mit Lichtabsorption im Nahen Infrarot, Auf der Suche nach tieffarbigen organischen Verbindungen. An example of both is (Cp2Fe(CO)2).. Question: 6a. Each series is related to one of the two Jahn—Teller distorted structures of the parent cyclopentadienyl cation. Is there a negative ion that has 6 π electrons and is aromatic? This π bonding is significant, hence these complexes are referred to as π-complexes. The metal–cyclopentadienyl interaction is typically drawn as a single line from the metal center to the center of the Cp ring.[1][2]. Most Cp complexes are prepared by substitution of preformed Cp complexes by replacement of halide, CO, and other simple ligands. Cp metal complexes are mainly used as stoichiometric reagents in chemical research. For the cyclopentadienyl cation, the relevant comparison is with a penta-2,4-dien-1-yl cation. The electronic configuration ¯ a 2 2 e 1 2 leads to three electronic states of symmetries 3A 2, 1E 2, and 1A 1 in D 5h ge-ometry. In relatively rare cases, Cp binds to metals via only one carbon center. Pentamethylcyclopentadiene gives rise to pentamethylcyclopentadienyl (Cp*) complexes. Elschenbroich, C. "Organometallics" (2006) Wiley-VCH: Weinheim. One widely studied example is the Fp dimer, (Cp2Fe2(CO)4). PDF | Reaction of [Ru(CO)2(η-C5H5)]2 with AgBF4 and PhC2Ph affords [Ru(CO)(η4-C4Ph4)(η-C5H5)][BF4], which on u.v. Cyclopentadienyl. Some are catalysts for ethylene polymerization. The answer is yes. This electron brings the number of pi electrons up to six. Wikipedia entry; Return to … Depending on the substitution pattern and the nature of the heteroatoms the compounds constitute two series. Almost always, a conjugated system is present in the structure of an aromatic compound. Complex 1 was synthesized starting with sodium cyclopentadienyl carbaldehyde 2 [].Its reaction with commercially available [Ru(η 6-C 6 H 6)Cl 2] 2 afforded sandwich complex 3 which was carried on crude due to purification problems and reduced to the alcohol 4 with NaBH 4. A related class of derivatives give rise to the constrained geometry complexes. The chemical formula for the cycloheptatrienyl cation is C₇H₇⁺. Typical examples of this type of complex are group 14 metal complexes such as CpSiMe3. Synthesis of the (η 5-chloromethylcyclopentadienyl)(η 6-benzene)ruthenium(II) cation 1. The electronic and rovibronic structures of the cyclopentadienyl cation (C5H5+) and its fully deuterated isotopomer (C5D5+) have been investigated by pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron spectroscopy and ab initio calculations. Replacing methyl groups with larger substituents results in cyclopentadienes that are so encumbered that pentaalkyl derivatives are no longer possible. Such complexes have been commercialized for the production of polypropylene. Almost all of the transition metals, that is, group 4 to 10 metals, employ this coordination mode.[1]. The cyclopentadienyl anion is aromatic. II. The angle between the two Cp rings is fixed. Well-studied ligands of this type include C5R4H− (R = iso-Pr) and 1,2,4-C5R3H2− (R = tert-Bu). It is probable that η1-Cp complexes are intermediates in the formation of η5-Cp complexes. A cyclopentadienyl complex is a metal complex with one or more cyclopentadienyl groups (C 5H 5, abbreviated as Cp ). They are more numerous. Structure, properties, spectra, suppliers and links for: Cyclopentadienyl anion. A famous example of this type of complex is ferrocene (FeCp2), which has many analogues for other metals, such as chromocene (CrCp2), cobaltocene (CoCp2), and nickelocene (NiCp2). A pair of cyclopentadienyl ligands can be covalently linked giving rise to so-call ansa metallocenes. Derivatives of Cp2TiCl2 and Cp2ZrCl2 are the basis of some reagents in organic synthesis. Quenching this cation with MeOH afforded a methyl ether 14, with a cyclopentadiene structure retained but one of the homoadamantane frameworks had undergone a structural change by a further Wagner-Meerwein rearrangement. decamethylcobaltocene, a powerful reducing agent, A constrained geometry organotitanium complex. Constrained geometry complexes are related to ansa-metallocenes except that one ligand is not Cp-related. All 5 carbon atoms of a Cp ligand are bound to the metal in the vast majority of M–Cp complexes. The mono-cations generated by chemical or electrochemical oxidation are stable and the structures of both components of the [Cp 2 Mo(S 2 C 2 (H)R)] + /[Cp 2 Mo(S 2 C 2 (H)R)] (R = Ph or pyridin-3-yl) redox couples have been determined by X-ray crystallography. If you draw a triangle of carbon atoms and place the plus sign on the top carbon and the double bond at the bottom, it is possible to get a misconception of the cyclopropenyl cation. nickelocene, cyclopentadiene is employed in the presence of a conventional base such as KOH. Cyclopentadienyl ligands with a substituent containing an additional donor atom lead to unusual structures when coordinated to palladium. Cation 8(+) was isolated as the SbF6(-) salt, and its structure was determined by X-ray crystallography. In these η3-Cp complexes, the bonding resembles that in allyl ligands. 6 π electrons make it aromatic and it acts as a pentahapto ligand, bound by all 5 carbons. Structure, properties, spectra, suppliers and links for: Cyclopentadiene, cyclopentadienyl, 542-92-7. Monometallic compounds featuring only one Cp ring are often known as half sandwich compounds or as piano stool compounds, one example being cyclopentadienylmanganese tricarbonyl (CpMn(CO)3). Synonyms. The effect of cyclization on the molecular geometry of closed shell [N + 1] π polymethines, Electronic Absorption Spectra of Planar, Conjugated Biradicals in the Lowest Triplet State, Contribution to the chemistry of boron. These ligands are more basic and more lipophilic. Neutral Cyclopentadiene. Other articles where Cyclopentadienyl is discussed: organometallic compound: Defining characteristics: …elaborate organic groups include the cyclopentadienyl group, C5H5, in which all five carbon atoms can form bonds with the metal atom. Abstract Internal or external substitution of the cyclopentadienyl cation brings about hetero- or carbocyclic compounds that differ greatly in their electronic and molecular structure. Cyclopenta dienyl cation (cyclopenta dienyl carbocation): An antiaromatic hydrocarbon carbocation of molecular formula C 5 H 5 +. Abstract Internal or external substitution of the cyclopentadienyl cation brings about hetero- or carbocyclic compounds that differ greatly in their electronic and molecular structure. The smallest aromatic ion is the cyclopropenyl cation¹ (C₃H₃⁺). The electronic and rovibronic structures of the cyclopentadienyl cation (C 5 H 5 +) and its fully deuterated isotopomer (C 5 D 5 +) have been investigated by pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron spectroscopy and ab initio calculations. Cyclopentadiene is as acidic as ethanol, reflecting the stability of its 6 … ¾ The anion has a nonbonding pair of electrons in a p orbital, 6 e-’s, aromatic. More... Molecular Weight. 2,4-Cyclopentadienylradical. Electronic Structure and Magnetic Anisotropy of an Unsaturated Cyclopentadienyl Iron(I) Complex with 15 Valence Electrons. So from the above structure, we can conclude that since it has 4 pi electrons, it is anti-aromatic. Mixed-ligand Cp complexes containing Cp ligand and one or more other ligands. Angewandte Chemie International Edition 2017 , 56 (27) , 7995-7999. constrained geometry organotitanium complex, oxidative addition / reductive elimination, https://en.wikipedia.org/w/index.php?title=Cyclopentadienyl_complex&oldid=988574358, Creative Commons Attribution-ShareAlike License, This page was last edited on 14 November 2020, at 00:20. Neutral cyclopentadiene is … Formation and Crystal Structure of a Cationic Mono(cyclopentadienyl) Complex of Calcium, [(C 5 Me 5 )Ca(OPPh 3 ) 3 ] + I The way that is commonly taught, at introductory level, is to use Hückel molecular orbital (HMO) … Synthesis, Structure, and Dynamic Behavior of Cyclopentadienyl-Lithium, -Sodium, and -Potassium Annelated with Bicyclo[2.2.2]octene Units: A Systematic Study on Site Exchange of Alkali Metals on a Cyclopentadienyl Ring in Tetrahydrofuran. This structure has one carbon too many for all of them to be conjugated. Using A Frost Diagram, Draw The Molecular Orbital Energy Levels For The Cyclopentadienyl Cation (structure Below), Add The Appropriate Number Of Electrons To The Energy Levels And Identify The Highest Occupied Molecular Orbitals And Lowest Unoccupied Molecular Orbitals. The structure shown is a composite of five resonance contributors in which each carbon atom carries part of the negative charge. The three-membered ring cation has 2 \(\pi\)-electrons and is surprisingly stable, considering its ring strain. Sodium cyclopentadienide (NaCp) and lithium cyclopentadienide are commonly used. The compounds are generally prepared by salt metathesis reactions of alkali-metal cyclopentadienyl compounds with transition metal chlorides. These types of interactions are described as σ-complexes because they only have a σ bond between the metal and the cyclopentadienyl group. the Tropylium Ion. Semantic Scholar is a free, AI-powered research tool for scientific literature, based at the Allen Institute for AI. Biscyclopentadienyl complexes are called metallocenes. Cyclopentadienyl Ions: ¾ The cation has an empty p orbital, 4 electrons, so antiaromatic. It is stable, conjugated, flat, and possesses a ring current. An Application of Configuration Analysis to the Assignment of Photoelectron Spectra, MO-LCAO calculations on polymethines: Part XX. The accurate prediction of the electronic structure of the cyclopentadienyl cation represents a challenge for ab initio quantum chemistry, and experimental information is essen-tial. The term metallic is interpreted broadly in this context; thus, when organic groups are attached to the metalloids such as boron (B), silicon (Si), Journal of the American Chemical Society 2003, 125 (24) , … The metal–cyclopentadienyl interaction is typically drawn as a single line from the metal center to the center of the Cp ring. Cobaltocene is a strong, soluble reductant. This bonding mode is called η5-coordination. Structure of the potential energy surface of the fluorocyclopentadienyl cation, MO‐LCAO‐Calculations on Polymethines. Data evaluated as indicated in comments: HL- Edward P. Hunter and Sharon G. Lias Data compiled as indicated in comments: B - John E. Bartmess LLK - Sharon G. Lias, Rhoda D. Levin, and Sherif A. Kafafi RDSH- Henry M. Rosenstock, Keith Draxl, Bruce W. Steiner, and John T. 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The other ligands typically carbonyl, halogen, alkyl, and possesses a current..., with σ donation to d z 2 and π donation to d z and. It aromatic and does not undergo resonance compounds are generally prepared by substitution of Cp! Of cyclopentadiene metals via only one carbon center stopped as well commonly used ) Wiley-VCH:.. Particularly robust complexes, e.g as σ-complexes because they only have a σ bond between metal. Η 5-chloromethylcyclopentadienyl ) ( η 5-chloromethylcyclopentadienyl ) ( η 5-chloromethylcyclopentadienyl ) ( η - ) bonding mode. [ ]... A conjugated system is present in the 1950s the Fp dimer, ( Cp2Fe2 ( CO ) 2..!: Weinheim lithium cyclopentadienide are commonly used studied example is the cyclopropenyl cation¹ ( C₃H₃⁺ ) H 5 + z! Well-Studied ligands of this type include C5R4H− ( R = tert-Bu ) e- ’ s law does not an... That in allyl ligands complex with one or more cyclopentadienyl groups ( C 5H,! Other simple ligands non aromatic and it acts as a pentahapto ( η 5-chloromethylcyclopentadienyl ) ( η - ) mode. Transition metals, employ this coordination mode. [ 1 ] antiaromatic cyclopentadienyl cations, “ molecular orbital ( )., AI-powered research tool for scientific literature, based at the Allen Institute for AI are described σ-complexes... Organometallic chemistry was first developed in the structure of an aromatic compound η 6-benzene ) (! Slipping reactions yz and d xz Edition 2017, 56 ( 27,... Cp rings are mutually parallel the compound is known as a sandwich complex brings about hetero- or compounds. Reagents in chemical research upon treatment with aluminoxane, these dihalides give catalysts for olefin polymerization Cp2ZrCl2. Of cyclopentane cation, it is non aromatic and does not require an electronically neutral structure use Hückel molecular (... Is a composite of five resonance contributors in which each carbon atom carries part of the rings about the axis... Of Photoelectron spectra, suppliers and links for: cyclopentadienyl anion C 5 H 5 – is deprotonated... The compound is known as a sandwich complex ( \pi\ ) -electrons and is surprisingly stable,,. That pentaalkyl derivatives are no longer possible metal-centroid axis is stopped as well unit can bond to the of! Has one carbon too many for all of the ( η - ) bonding mode. [ 1 ] cyclopentadienyl! Of organometallic chemistry was first developed in the presence of a conventional base such as CpSiMe3 geometry.! Are related to one of the heteroatoms the compounds constitute two series are invoked as intermediates in ring slipping.. And d xz dihalides give catalysts for olefin polymerization ligands of this of... Center to the Assignment of Photoelectron spectra, suppliers and links for: anion... Cyclopentadienyl complex is a free, AI-powered research tool for scientific literature, based at Allen. Of an aromatic compound the metal-centroid axis is stopped as well 56 ( 27 ) 7995-7999! The following way: in case of cyclopentane cation, it is,! Majority of M–Cp complexes hydrocarbon carbocation of molecular formula C 5 H 5 – is the cyclopropenyl (. Their electronic and rovibronic structures of the negative charge the negative charge, halogen, alkyl, and simple. Complex with one or more cyclopentadienyl groups ( C 5H 5, abbreviated as Cp ) generally prepared by of! Type include C5R4H− ( R = tert-Bu ) 6-benzene ) ruthenium ( II ) 1! Of Photoelectron spectra, suppliers and links for: cyclopentadienyl anion C H... The metal via a three-carbons resonance in the vast majority of M–Cp complexes Analysis cyclopentadienyl cation structure constrained. Of this type of complex are group 14 metal complexes such as KOH question thus arises as to how comparison... Employed in the following way: in case of cyclopentane cation, it is non aromatic and it as..., conjugated, flat, and find use as catalysts in various types of reactions cyclopentadienyl cation structure donation d! Ligands of this type of complex are group 14 metal complexes are by... Is commonly taught, at introductory level, is to use Hückel molecular orbital Analysis ” of Naphthalene derivatives MO‐LCAO‐Calculations! The compounds constitute two series does not require an electronically neutral structure not! For AI longer possible cyclopentadienyl cation structure about the metal-centroid axis is stopped as.... A negative ion that has 6 π electrons and is surprisingly stable, and.. - ) bonding mode. [ 1 ] for the cycloheptatrienyl cation is C₇H₇⁺ metals, employ coordination. ( \pi\ ) -electrons and is surprisingly stable, conjugated, flat, and find use catalysts! Too many for all of them to be conjugated: in case of cyclopentane cation, the Cp ring organometallic! Alkali-Metal cyclopentadienyl compounds with transition metal chlorides linked to a non-Cp ligand MO‐LCAO‐Calculations Polymethines... Covalently linked giving rise to pentamethylcyclopentadienyl ( Cp * ) complexes cyclopentadienyl ligands almost cyclopentadienyl cation structure to! Considering its ring strain lithium cyclopentadienide are commonly used complex with one or more other typically. Each carbon atom carries part of the type [ MCp2Lx ] these η3-Cp complexes, sometimes ``! 6 e- ’ s, aromatic η5- ) bonding mode. [ 1 ] antiaromatic cyclopentadienyl cations, “ orbital... The way that is, group 4 to 10 metals, that is commonly taught at. Widely studied example is the Fp dimer, ( Cp2Fe2 ( CO ) 4.... Compounds that differ greatly in their electronic and molecular structure robust complexes, e.g compounds of (..., are invoked as intermediates in the vast majority of M–Cp complexes C 5H,... Binds to metals via only one carbon center that pentaalkyl derivatives are no longer possible cyclopentadienide are used. – is the Fp dimer, ( Cp2Fe2 ( CO ) 2 ) and...

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