Difluorocarbene Complexes Research Articles

Synthesis of Ynones and γ-Butenolides with In Situ-Formed CO from a Palladium Difluorocarbene Complex

Synthesis of Ynones and γ-Butenolides with In Situ-Formed CO from a Palladium Difluorocarbene Complex

Spectroscopy and radiation-induced chemistry of an atmospherically relevant CH2F2…H2O complex: Evidence for the formation of CF2…H2O complex as revealed by FTIR matrix isolation and ab initio study

Difluoromethane is considered among the environment friendly alternatives to the ozone depleting chlorofluorocarbons. Due to its chemical inertness and lack of UV absorption above 200 nm, this compound can easily come to the upper layers forming complexes with widely abundant atmospheric components, such as water. The radiation-induced degradation of this compound and its complexes may be significant for reliable prediction of its long-term evolution in the environment as well as for development of new ways for its removal. In this work we have studied the vibrational spectroscopic properties and mechanisms of the radiation-induced decay of the CH2F2⋯H2O under the action of X-rays using matrix isolation FTIR spectroscopy and ab initio calculations. The IR spectrum of the complex in an argon matrix was characterized for the first time and assigned to a hydrogen-bonded structure with a binding energy of 11.1 kJ/mol (2.65 kcal/mol) (CCSD(T)/CBS level of theory). Complexation with water leads to a certain suppression of the efficiency of the radiation-induced decomposition of difluoromethane. The obtained results provide evidence for the radiation-induced formation of previously unreported CF2⋯H2O complex (in addition to other oxygen containing molecules, such as COF2 and CO). As demonstrated by calculations, the new difluorocarbene complex reveals a hydrogen bond and it is characterized by a binding energy of 5.73 kJ/mol (1.37 kcal/mol) (CCSD(T)/CBS level of theory).

Gold Difluorocarbenoid Complexes: Spectroscopic and Chemical Profiling

AbstractGold carbenes of the general type [LAu=CR2]+ are sufficiently long‐lived for spectroscopic inspection only if the substituents compensate for the largely missing stabilization of the carbene center by the [LAu]+ fragment. π‐Donation by two fluorine substituents (R=F) is insufficient; rather, difluorocarbene complexes are so deprived in electron density that they sequester even “weakly coordinating” anions such as triflate or triflimide. This particular bonding situation translates into unmistakable carbenium ion chemistry upon reaction with stilbene as a model substrate.

Gold Difluorocarbenoid Complexes: Spectroscopic and Chemical Profiling.

Gold carbenes of the general type [LAu=CR2 ]+ are sufficiently long-lived for spectroscopic inspection only if the substituents compensate for the largely missing stabilization of the carbene center by the [LAu]+ fragment. π-Donation by two fluorine substituents (R=F) is insufficient; rather, difluorocarbene complexes are so deprived in electron density that they sequester even "weakly coordinating" anions such as triflate or triflimide. This particular bonding situation translates into unmistakable carbenium ion chemistry upon reaction with stilbene as a model substrate.

Regioselective Syntheses of Fluorinated Cyclopentanone Derivatives: Ring Construction Strategy Using Transition-Metal–Difluorocarbene Complexes and Free Difluorocarbene

The syntheses of fluorinated cyclopentanone derivatives, which have pharmaceutical and agrochemical importance are reported. The catalytic reaction of copper(I) and nickel(II) difluorocarbenes with silyl dienol ethers afforded 4,4-difluoro- and 5,5-difluorocyclopent-1-en-1-yl silyl ethers, respectively. The fluorine-directed and -activated Nazarov cyclization of 1-fluorovinyl vinyl ketones, which were prepared from silyl dienol ethers and free difluorocarbene, proceeded efficiently to afford 2-fluorocyclopent-2-en-1-ones. Moreover, fluorine-­directed Nazarov cyclizations of 2,2-difluorovinyl vinyl ketones and 1-(trifluoromethyl)vinyl vinyl ketones afforded 3-fluorocyclopent-2-en-1-ones and 5-(trifluoromethyl)cyclopent-2-en-1-ones, respectively. In addition, derivatization of ring-difluorinated products also provided 3-fluorocyclopent-2-en-1-ones.

Communication: A hydrogen-bonded difluorocarbene complex: Ab initio and matrix isolation study.

Structure and spectroscopic features of the CF2⋯HF complexes were studied by ab initio calculations at the CCSD(T) level and matrix isolation FTIR spectroscopy. The calculations predict three stable structures. The most energetically favorable structure corresponds to hydrogen bonding of HF to the lone pair of the C atom (the interaction energy of 3.58 kcal/mol), whereas two less stable structures are the H⋯F bonded complexes (the interaction energies of 0.30 and 0.24 kcal/mol). The former species was unambiguously characterized by the absorptions in the FTIR spectra observed after X-ray irradiation of fluoroform in a xenon matrix at 5 K. The corresponding features appear at 3471 (H-F stretching), 1270 (C-F symmetric stretching, shoulder), 1175 (antisymmetric C-F stretching), and 630 (libration) cm-1, in agreement with the computational predictions. To our knowledge, it is the first hydrogen-bonded complex of dihalocarbene. Possible weaker manifestations of the H⋯F bonded complexes were also found in the C-F stretching region; however, their assignment is tentative. The H⋯C bonded complex is protected from reaction yielding a fluoroform molecule by a remarkably high energy barrier (23.85 kcal/mol), so it may be involved in various chemical reactions.

D8 Nickel and palladium difluorocarbenes derived from trifluoromethyl POCOP-type pincer complexes

In this study, trifluoromethyl POCOP-type pincer complexes (iPrPOCOP)Ni(CF3) (1-CF3) and (iPrPOCOP)Pd(CF3) (2-CF3) are prepared. These complexes undergo Lewis acid-mediated fluoride abstraction to furnish cationic d8 difluorocarbene complexes of the type [(iPrPOCOP)M(=CF2)]+[X]-, which are characterized in solution and for M = Ni using single-crystal X-ray diffraction analysis. The electrophilic nature of these difluorocarbene complexes is discussed, including their reactivity with pyridines.

Copper(I)-Catalyzed [4 + 1] Cycloaddition of Silyl Dienol Ethers with Sodium Bromodifluoroacetate: Access to β,β-Difluorocyclopentanone Derivatives.

Silyl dienol ethers readily underwent copper(I)-catalyzed [4 + 1] cycloaddition with sodium bromodifluoroacetate to afford 4,4-difluorocyclopent-1-en-1-yl silyl ethers. On the basis of high-resolution mass spectroscopy analysis, annulation presumably proceeded via a copper(I) difluorocarbene complex, which represents an unprecedented example of [4 + 1] cycloadditions promoted by a transition metal difluorocarbene complex.

Pd-Catalyzed Transfer of Difluorocarbene.

The study of transition-metal difluorocarbene complex has long been a subject of active investigation, but the transition-metal-catalyzed transfer of difluorocarbene remains a significant challenge. The Pd-catalyzed transfer of difluorocarbene is described to realize the coupling reaction of boronic acids with difluorocarbene to give (difluoromethyl)arenes and -olefins. Mechanistic investigations reveal that the Pd═CF2 complex is an important intermediate for this transformation. This complex is prone to trimerization without the presence of starting materials.

ChemInform Abstract: Cross‐Coupling Between Difluorocarbene and Carbene‐Derived Intermediates Generated from Diazocompounds for the Synthesis of gem‐Difluoroolefins.

Cross-coupling between difluorocarbene and carbene-derived intermediates generated from diazocompounds was developed to give gem-difluoroolefins, which constitutes a fast practical pathway to achieve hindered gem-difluoroolefins. The cross-coupling between difluorocarbene and aryl diazoacetates proceeded smoothly in the presence of a copper source, whereas its coupling with diaryl diazomethanes occurred well under metal-free conditions. A mechanism involving a copper–difluorocarbene complex was proposed.

Perfluoroalkyl Cobalt(III) Fluoride and Bis(perfluoroalkyl) Complexes: Catalytic Fluorination and Selective Difluorocarbene Formation.

Four perfluoroalkyl cobalt(III) fluoride complexes have been synthesized and characterized by elemental analysis, multinuclear NMR spectroscopy, X-ray crystallography, and powder X-ray diffraction. The remarkable cobalt fluoride (19)F NMR chemical shifts (-716 to -759 ppm) were studied computationally, and the contributing paramagnetic and diamagnetic factors were extracted. Additionally, the complexes were shown to be active in the catalytic fluorination of p-toluoyl chloride. Furthermore, two examples of cobalt(III) bis(perfluoroalkyl)complexes were synthesized and their reactivity studied. Interestingly, abstraction of a fluoride ion from these complexes led to selective formation of cobalt difluorocarbene complexes derived from the trifluoromethyl ligand. These electrophilic difluorocarbenes were shown to undergo insertion into the remaining perfluoroalkyl fragment, demonstrating the elongation of a perfluoroalkyl chain arising from a difluorocarbene insertion on a cobalt metal center. The reactions of both the fluoride and bis(perfluoroalkyl) complexes provide insight into the potential catalytic applications of these model systems to form small fluorinated molecules as well as fluoropolymers.

D10 Nickel Difluorocarbenes and Their Cycloaddition Reactions with Tetrafluoroethylene

We report the first isolable nickel difluorocarbene complexes (NiP2[P(OMe)3](═CF2); P2 = Ph2P(CH2)2PPh2, 2 P(OMe)3), which are also the only examples of formally d10 metal fluorocarbenes. These [Ni0]═CF2 complexes react with tetrafluoroethylene (TFE) to yield the rare perfluorometallacyclobutanes [NiP2(κ2-CF2CF2CF2−)], with potential relevance to fluoroalkene metathesis and polymerization. Preliminary kinetic experiments establish that the reactions of the new [Ni]═CF2 compounds with TFE are considerably faster than the analogous reactions of their previously reported [Co]═CF2 counterparts. Further, we show that TFE addition to 2 is a dissociative process, in contrast to [Co]═CF2, which reacts with TFE in an associative fashion. Finally, the preliminary reactivity of NiP2(κ2-CF2CF2CF2−) (P2 = Ph2P(CH2)2PPh2) is described.

Regioselective Synthesis of α,α-Difluorocyclopentanone Derivatives: Domino Nickel-Catalyzed Difluorocyclopropanation/Ring-Expansion Sequence of Silyl Dienol Ethers.

Silyl dienol ethers prepared from α,β-unsaturated ketones underwent nickel-catalyzed difluorocyclopropanation of the electron-rich alkene moiety with trimethylsilyl 2,2-difluoro-2-(fluorosulfonyl)acetate. The subsequent vinylcyclopropane-cyclopentene rearrangement afforded silyl 5,5-difluorocyclopent-1-en-1-yl ethers in good yields. The obtained five-membered silyl enol ethers were demonstrated to be versatile intermediates for the synthesis of di- and monofluorinated cyclopentanones and cyclopentenones. A nickel difluorocarbene complex is proposed as a key intermediate in the difluorocyclopropanation.

A New Stepwise Mechanism for Formation of a Metallacyclobutane via a Singlet Diradical Intermediate

Density functional calculations (M06/def2-TZVP//M06/LACVP** in THF solvent) reveal that the formation of a perfluorometallacyclobutane from tetrafluoroethylene, C2F4 (TFE), and the difluorocarbene complex CoCp(PPh2Me)(CF2) is highly exothermic and involves a stepwise [2 + 2] cycloaddition mechanism with a 1,4-singlet diradical intermediate. This pathway is significantly lower in energy than pathways involving initial η1 or η2 binding of TFE to cobalt. The stability of the singlet-diradical intermediate results from the formation of a strong CF2–CF2 bond coupled with the radical stabilizing effect of a difluoromethylene group. A concerted [2 + 2] transition state between the 18-electron complex CoCp(PPh2Me)(CF2) and TFE is very high in energy and essentially forbidden.

Tetracarbonyl(trifluoromethyl)cobalt(I) [Co(CO)4(CF3)] as a Precursor to New Cobalt Trifluoromethyl and Difluorocarbene Complexes

An improved synthesis of the known trifluoromethyl cobalt compound Co(CO)4(CF3) (1), which gives significantly higher yields than previously reported methods, allows for an investigation of its carbonyl substitution chemistry. Treatment of 1 with P-donor ligands of varying denticity under thermal conditions afforded Co[P(O-o-tolyl)3](CO)3(CF3) (2), Co(DPPE)(CO)2(CF3) (3), and Co(P3)(CO)(CF3) (4) in high isolated yields [DPPE = Ph2PCH2CH2PPh2; P3 = PhP(CH2CH2PPh2)2]. The new cobalt N-heterocyclic carbene complex Co(SIPr)(CO)3(CF3) (5) [SIPr = 1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene)] was obtained by phosphine substitution from Co(PPh3)(CO)3(CF3), a known compound efficiently prepared from 1. Additionally, we report the synthesis of two rare cobalt difluorocarbene complexes ([Co] = CF2) produced by fluoride abstraction from 3 or 4. These results are relevant to our efforts to assess the reactivity of first-row metal perfluoroalkyl and fluorocarbene complexes.

A Simple Route to Difluorocarbene and Perfluoroalkylidene Complexes of Iridium

Primary perfluoroalkyl compounds of iridium undergo facile two-electron reduction to afford a simple route to difluorocarbene and perfluoroalkylidene complexes, two of which have been crystallographically characterized. Low-temperature protonation reactions illustrate that the thermodynamic site of protonation depends on the nature of the fluorinated carbene; the difluorocarbene complex undergoes protonation at iridium, while its perfluoroethylidene congener undergoes protonation at carbon.

Carbamoyl (Carboxamido) Complexes as Precursors for Metallaoxetene, Isonitrile, and Aminomethylidyne Complexes of Iron

The reaction of [Fe{C(O)NiPr2}(CO)4]Li with (CF3CO)2O in diethyl ether followed by triphenylphosphine provides carbamoyl complexes [Fe{η2-OCNiPr2}(CF3)(CO)2(PPh3)] (1) or [Fe(η2-OCNiPr2)(CO)2(PPh3)2](O2CCF3) (2a·O2CCF3) depending on the reaction conditions. The same procedure performed in dichloromethane provides the aminomethylidyne complex [Fe(⋮CNiPr2)(CO)3(PPh3)](O2CCF3) (5·O2CCF3) as well as traces of [Fe(η2-OCNiPr2)(CO)2(PPh3)2](O2CCF3) (2a·O2CCF3). The reactions of 1 with moist AgBF4 or HBF4 provide [Fe{η2-OCNiPr2}(CO)3(PPh3)]BF4 (2b·BF4), via a putative difluorocarbene intermediate, [Fe{η2-OCNiPr2}(CF2)(CO)2(PPh3)]BF4. In a similar manner, [Fe(η2-OCNiPr2)(CF3)(CO)(dppe)] (3) (obtained from 1 and dppe) reacts with HBF4(aq) to provide [Fe{η2-OCNiPr2}(CO)2(dppe)]BF4 (4·BF4). A difluorocarbene complex is also implicated in the formation of the ferraoxetene [Fe{κ2-C(NiPr2)OCF2}(CO){HB(pz)3}] (6) (pz = pyrazol-1-yl), which results from treatment of 1 with K[HB(pz)3] under high dilution. Under more concen...

Synthesis and molecular structure of a molybdenum difluorocarbene complex, [(.eta.5-C5Me5)Mo(CO)3(CF2)]OSO2CF3

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis and molecular structure of a molybdenum difluorocarbene complex, [(.eta.5-C5Me5)Mo(CO)3(CF2)]OSO2CF3Johnson D. Koola and Dean M. RoddickCite this: Organometallics 1991, 10, 3, 591–597Publication Date (Print):March 27, 1991Publication History Published online1 May 2002Published inissue 27 March 1991https://doi.org/10.1021/om00049a017RIGHTS & PERMISSIONSArticle Views252Altmetric-Citations39LEARN 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 InReddit PDF (919 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

ChemInform Abstract: Synthesis, Structure, and Reactivity of a Bridging Difluorocarbene Complex, (CpFeIr(Cl)(CO)2(PMe2Ph)2(μ‐CO)(μ‐CF2)) (BF4)·CH2Cl2.

AbstractThe moisture‐sensitive, heterobimetallic complex (IIIa) is prepared by the oxidative addition of (I) to (II).

Oxidation state control of the reactivity of a transition metal–carbon double bond. Synthesis, X-ray crystal structure, and reactions of the zerovalent difluorocarbene complex [Ru(CF2)(CO)2(PPh3)2

Reaction of [Ru(CO)2(PPh3)3] with [Cd(CF3)2(MeOCH2CH2OMe)] produces the zerovalent CF2-complex, [Ru(CF2)(CO)2(PPh3)2]; X-ray crystal structure determination reveals very distorted trigonal bipyramidal geometry and an RuC distance of 1.83(1)A, and reaction indicate that when compared with an RuII CF2-complex, the CF2-ligand in the zerovalent compound has greatly reduced reactivity towards nucleophiles and in fact reacts with the electrophiles HCL and Ag+ giving [Ru(CF2H)Cl(CO)2(PPh3)2] and [[graphic omitted]{H2O})(CO)2(PPh3)2]+, respectively.