Vinylidene Groups Research Articles

Synthesis and reactivity of ditungsten helical complex W 2(CO) 6(μ-Ph 2PCCPPh 2) 3

Reaction of W(CO) 3(Me 3tach) (Me 3tach1,3,5-trimethyl-1,3,5-triazacyclohexane) with Ph 2PCCPPh 2 at room temperature affords a triply-bridged complex W 2(CO) 6(μ-Ph 2PCCPPh 2) 3 ( 1) and a vinylidene complex W 2(CO) 6(μ-Ph 2PCCPPh 2)[μ-C 4H(PPh 2) 3] ( 2). Compound 2 can be obtained by treating 1 with Me 3tach in dichloromethane. The crystal structures of 1 and 2 are determined by an X-ray diffraction study. The structure of 1 depicts a helical M 2L 3 framework with an idealized D 3 symmetry. The vinylidene group of 2 is not linear, with the WCC bond angle of 158.6(4)°.

Synthesis of indenyl-ruthenium(II) σ-alkynyl complexes via nucleophilic addition of (1 R)-(+)- and (1 S)-(−)-camphor enolates on the allenylidene group of [Ru(CCCPh 2)(η 5-C 9H 7)(PPh 3) 2][PF 6]: Efficient synthesis of novel optically pure vinylidene derivatives

The diphenylallenylidene complex [Ru(CCCPh 2)(η 5-C 9H 7)(PPh 3) 2][PF 6] ( 1) regioselectively reacts at the C γ atom with the lithium enolate derived from (1 R)-(+)-camphor to yield σ-alkynyl derivative [Ru{CCCPh 2(C 10H 15O)}(η 5-C 9H 7)(PPh 3) 2] ( 2). Complex 2 was obtained as a non-separable mixture of two diastereoisomers, i.e. (1 R,3 S,4 R)- 2 and (1 R,3 R,4 R)- 2 (ca. 3:2 ratio), in which the alkynyl fragment is located in exo or endo disposition on the camphor skeleton, respectively. Protonation of this mixture with HBF 4·Et 2O affords the vinylidene derivative [Ru{CC(H)CPh 2(C 10H 15O)}(η 5-C 9H 7)(PPh 3) 2][BF 4] ( 3) as a single diastereoisomer, i.e. (1 R,3 S,4 R)- 3, showing an exo disposition of the vinylidene group. The structure of complex (1 R,3 S,4 R)- 3 has been confirmed by X-ray diffraction. The molecular structure shows the typical pseudo-octahedral three-legged piano-stool geometry around the ruthenium atom, which is linked to the phosphorus atoms of the PPh 3 ligands, to the η 5-bonded indenyl ligand, and to an almost linear vinylidene chain (RuC(1)C(2)=165.6 (18)°) with a RuC(1) bond length of 1.88 (2) Å. Demetalation of (1 R,3 S,4 R)- 3, by treatment with acetonitrile at reflux, yields the terminal alkyne HCCCPh 2(C 10H 15O) ( 4) and the nitrile complex [Ru(NCMe)(η 5-C 9H 7)(PPh 3) 2][BF 4] ( 5). Compound 4 was obtained as a non-separable mixture of two diastereoisomers, i.e. (1 R,3 S,4 R)- 4 and (1 R,3 R,4 R)- 4 (ca. 3:1 ratio). Related reactions starting from diphenylallenylidene 1 and the (1 S)-(−)-camphor enolate are also reported.

Vibrational Spectroscopic and Conformational Analysis of Pinosylvin

Infrared and Raman spectra of pinosylvin were recorded and the vibrational frequencies with the corresponding infrared intensities were compared with the results of ab initio calculations utilizing the DFT method with the Becke3P86 functional and the 6-31G(d) basis set. Normal coordinate analysis was carried out. The effect of the conformation of the OH groups on the distribution of net charges, molecular energy and vibrational fundamentals were analyzed. One of the OH-cis−OH-trans conformers has the lowest energy. The conformation has a strong effect on the aforementioned properties, e.g., the cis-to-trans transition generates electron repulsion toward the vinylidene group between the two benzene rings. The changes in the different properties are in good accordance with each other. For comparison, the vibrational spectra were also recorded and calculated for the parent compound, trans-stilbene.

Synthesis of terminally functionalized polyolefines

Propylene-ethylene copolymer (PER), atactic polypropylene (PP) and atactic poly- 4-methyl-1-pentene (P4MP1) were prepared with a Cp2ZrCl2-methylaluminoxane catalyst system. These polymers containing terminal vinylidene groups were made to react with halogen, sulfuric acid, 9-borabicyclo [3,3,1] nonane (9-BBN) or percarboxylic acid, leading to terminally halogenated, hydrogen-sulfated, hydroxy-(OH)- or epoxy- functionalized polyolefines.

Synthesis and characterization of metallocene-catalyzed propylene–ethylene copolymer with end-capped functionality

Metallocene-catalyzed propylene–ethylene copolymer (PER) having a terminal vinylidene group, reacted with maleic anhydride without free radical conditions to prepare terminally MAH-functionalized PER. Through the analysis of the obtained polymer by 13C NMR spectroscopy, it was shown that a large part of a terminal vinylidene group isomerizes to a more stable internal double bond in this reaction and that the PER–MAH is formed via the reaction of MAH with isomerized PER and original PER.

Solid-state polypropylene grafting as an effective chemical method of modification

The role of vinylidene groups, formed by the action of organic peroxides, on crosslinking reactions in isotactic polypropylene (iPP), is discussed. Grafting of polymerizable monomers on powdered iPP, performed below its melting temperature, occurs with high efficiency, depending on the structure of peroxide used.

Ring-Opening Polymerization of 1-Methylene-2-phenylcyclopropane Catalyzed by a Pd Complex To Afford Regioregulated Polymers.

Selective 2,1-insertion of the monomer and subsequent elimination of the β-carbon atom of the growing polymer end is proposed as a new mechanism for polymer synthesis that involves ring opening of the monomer. A palladium complex promotes the ring-opening polymerization of 1-methylene-2-arylcyclopropanes to afford polymers with a vinylidene group in each monomer unit.

Sulfur–carbon bond formation and bond cleavage in alkynyl-bridged heterobinuclear complexes of rhodium and iridium

The phenylacetylide-bridged heterobinuclear complexes [RhIr(CO)2(μ-η1:η2-C2Ph)(dppm)2][X] (X=BF4, SO3CF3; dppm=Ph2PCH2PPh2) (1) react with carbon disulfide to give several products. At temperatures between −60 and −80°C the first product, [RhIr(CO)(η2-CS2)(μ-CO)(μ-η1:η2-C2Ph)(dppm)2][X] (2), is the result of CS2 coordination at Ir. Upon warming, two products are formed as a result of condensation of two CS2 groups. In [RhIr(CO)(μ-η1:η3-CC(Ph)SCSCS2)(μ-CO)(dppm)2][X] (3), the resulting C2S4 fragment has also condensed at the β-carbon of the acetylide group to give a heteroatom-substituted vinylidene group. The other identified product, [RhIr(CO)(C2S4)(μ-C2Ph)(μ-CO)(dppm)2][X] (4), is very similar to 3 apart from the absence of coupling of the C2S4 moiety and the acetylide group. Compound 3 appears to be formed independently of 4, but also slowly transforms into 4 by cleavage of a C-S bond. The reaction of 1 with nBuNCS at −80°C yields [RhIr(CO)(η2-SCNnBu)(μ-CCPh)(μ-CO)(dppm)2][X] (5), analogous to 2, and upon warming this rearranges to the isothiocyanate-bridged product [RhIr(CCPh)(CO)2(μ-SCNnBu)(dppm)2][X] (6). Compound 6 undergoes S-C bond cleavage to yield [RhIr(CCPh)(CO)(CNnBu)(μ-S)(μ-CO)(dppm)2][X] (7), slowly at ambient temperature or within hours under reflux. Although no simple adducts analogous to 5 and 6 were observed with tBuNCS, refluxing 1 in the presence of an excess of this substrate yields [RhIr(CCPh)(CO)(CNtBu)2(μ-S)2(dppm)2][X] (9) as the major product along with smaller amounts of [RhIr(CCPh)(CO)(CNtBu)(μ-S)(μ-CO)(dppm)2][X] (8), analogous to compound 7. Refluxing 1 in the presence of excess nBuNCS also yields some of the bis-n-butylisocyanide product, analogous to 9. The X-ray structures of compounds 3 (SO3CF3− salt), 7 (BF4− salt) and 9 (BF4− salt) are reported.

Higher ?-olefin polymerizations catalyzed byrac-Me2Si(1-C5H2-2-CH3-4-tBu)2Zr(NMe2)2/Al(iBu)3/[Ph3C][B(C6F5)4

Polymerizations of higher α-olefins, 1-pentene, 1-hexene, 1-octene, and 1-decene were carried out at 30 °C in toluene by using highly isospecific rac-Me2Si(1-C5H2-2-CH3-4-t Bu)2Zr(NMe2)2 (rac-1) compound in the presence of Al(iBu)3/[CPh3][B(C6F5)4] as a cocatalyst formulation. Both the bulkiness of monomer and the lateral size of polymer influenced the activity of polymerization. The larger lateral of polymer chain opens the π-ligand of active site wide and favors the insertion of monomer, while the large size of monomer inserts itself into polymer chain more difficultly due to the steric hindrance. Highly isotactic poly(α-olefin)s of high molecular weight (MW) were produced. The MW decreased from polypropylene to poly(1-hexene), and then increased from poly(1-hexene) to poly(1-decene). The isotacticity (as [mm] triad) of the polymer decreased with the increased lateral size in the order: poly(1-pentene) > poly(1-hexene) > poly(1-octene) > poly(1-decene). The similar dependence of the lateral size on the melting point of polymer was recorded by differential scanning calorimetry (DSC). 1H NMR analysis showed that vinylidene group resulting from β-H elimination and saturated methyl groups resulting from chain transfer to cocatalyst are the main end groups of polymer chain. The vinylidene and internal double bonds are also identified by Raman spectroscopy. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1687–1697, 2000

C−H Bond Activation and C−C Bond Formation in the Reactions of the Methyl Complex [Ir2(CH3)(CO)2(Ph2PCH2PPh2)2][CF3SO3] with Alkynes

The methyl complex [Ir2(CH3)(CO)(μ-CO)(dppm)2][CF3SO3] (1) reacts readily with a variety of alkyne molecules. With alkynes containing electron-withdrawing substituents (RC⋮CR‘; R = R‘ = CO2Me, CF3; R = CO2Me, R‘ = H), the alkyne-bridged products, [Ir2(CH3)(CO)2(μ-alkyne)(dppm)2][CF3SO3], result. With other 1-alkynes (HC⋮CR, R = Me, Ph) reaction at −80 °C results in oxidative addition to give acetylide hydrides [Ir2H(CH3)(CO)2(μ-C2R)(dppm)2][CF3SO3], which upon warming undergo transfer of the hydride ligand to the β-carbon of the acetylide to give the vinylidene-bridged products. At ambient temperature methane elimination occurs, yielding the acetylide-bridged “A-frames”, [Ir2(CO)2(μ-C2R)(dppm)2][CF3SO3]. Reaction of 1 with 1 equiv of acetylene proceeds through analogous acetylide and vinylidene intermediates; however under carbon monoxide exchange of a vinylidene hydrogen and the methyl ligand occurs to give a methylvinylidene-bridged hydride [Ir2(H)(CO)3(μ-CCHMe)(dppm)2][CF3SO3]. Reaction of 1 with an excess of acetylene results in the incorporation of two acetylene molecules, giving [Ir2(CH3)(C2H)(CO)2(μ-H)(μ-CCH2)(dppm)2][CF3SO3], containing terminal methyl and acetylide ligands and bridging hydride and vinylidene groups. Reaction of 1 with a number of internal, nonactivated alkynes results first in the formation of the alkyne-bridged products, which slowly rearrange to the unusual species [Ir2H(CO)2(μ-CHCRC(H)R)(dppm)2][CF3SO3], in which cleavage of two C−H bonds of the methyl group has occurred accompanied by condensation of the resulting methyne group at one end of alkyne linkage and transfer of a hydrogen to the other end. The resulting hydrocarbyl moiety can be viewed as a vinylcarbene. The X-ray structures of three representative products are reported, including one of these vinylcarbenes (R = C2H5).

Reactivity of Aluminum-Functionalized Isotactic Polypropylene with Molecular Oxygen

The efficiency of the synthesis of terminally hydroxylated isotactic polypropylene (i-PP) through the oxidation of Al-functionalized i-PP was evaluated and side-reactions are discussed. Al-functionalized i-PP was prepared by chain-transfer reaction by Et3Al with the MgCl2-TiCl4-dioctylphthalate/Et3Al/diphenyldimethoxysilane catalyst. It was oxidized by molecular oxygen and poured into methanol for alcoholysis at chain ends. All chain-end groups of the obtained polymer were identified by 13C NMR and 52 mol% of Al-functionalized chain ends was found converted to hydroxyl groups. 20 mol% vinylidene groups by elimination of β-hydrogen and 8 mol% vinyl groups by elimination of β-methyl groups were detected. 20 mol% of Al-functionalized chain ends remained unreacted. IR analysis of the resulting i-PPs showed the hydroxyl groups at ω-ends to form no hydrogen bond and decrease in reaction time with molecular oxygen to lead to lower conversion to terminally hydroxylated chain ends.

Composition and Structure of Liquid Polysulfide Oligomers Based on Sulfur, Styrene and Methacrylic Acid

Liquid polysulfide oligomers have been prepared in bulk as well as under the conditions of known methods. Styrene, methacrylic acid and sulfur were used as starting materials. The composition of the oligomer products was determined by using IR spectroscopy as the principal method. The absorption bands at 1600 and 700 cm−1 for styrene and 1697 cm−1 for methacrylic acid were employed as an analytical tool. Both the kind of chemical bonds between the monomer fragments and length of polysulfide bonds were studied by the combined application of IR and 1H NMR spectroscopy. Methacrylic acid was found to be bound chemically to the sulfur atoms via its vinylidene group and the class of polysulfidity decreased from 2.8 to 2.5. The oligomers synthesized were introduced into elastomer compositions utilized for the packing of high-voltage cable sleeves. An improvement of the adhesive properties towards metal surfaces by 43 % was observed as oligomer containing 10.3 mol % of methacrylic acid fragments was employed.

1,1-Bis(1″,2″,3″,4″,5″-pentamethylferrocen-1′-yl)ethene

1,1-Bis(1″,2″,3″,4″,5″-pentamethylferrocen-1′-yl)ethene ( 6) was synthezised as a prototype of two metallocenes that are bridged by the sp 2-carbon center of a vinylidene group. Starting from 6- N, N-dimethylamino-6-methylfulvene, the iron-containing intermediates were a pentamethylferrocenyl-substituted fulvene and an ethene that was geminally disubstituted by a Cp anion and a pentamethylferrocenyl moiety. Besides other methods, the ferrocenes were characterized by NMR spectroscopy including full signal assignment. The bimetallic compound 6 showed moderate interactions between the two ferrocenes in the cyclic voltammogram (Δ E 1/2=150 mV). According to X-ray crystal structure analysis compound 6 is a twisted molecule; the vinylidene moiety and the Cps of the neighboring ferrocenes are not coplanar.

Alder Ene functionalization of polypropylene through reactive extrusion

A commercial isotactic polypropylene was degraded to increase its terminal vinylidene group concentration, and it was subsequently functionalized with maleic anhydride through the Alder Ene reaction at temperatures above 200°C in a co-rotating twin screw extruder. Characterization of the maleated product by Fourier transform infrared spectroscopy, 1H NMR, differential scanning calorimetry, and gel permeation chromatography showed the anhydride group to be terminally attached, and the degree of functionalization was determined by infrared analysis. Increased temperature and maleic anhydride concentration, as well as improved mixing in the extruder, were found to improve the extent of the reaction. The catalytic contribution of Lewis acid species was evaluated, and ruthenium chloride was found to increase the extent of the reaction by 16% in comparison with stannous chloride as a catalyst in the Alder Ene reaction. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 503–516, 1999

Metal Vinylidenes in Catalysis

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMetal Vinylidenes in CatalysisChristian Bruneau and Pierre H. DixneufView Author Information Université de Rennes, CNRS (UMR 6509), Laboratoire de Chimie de Coordination et Catalyse Campus de Beaulieu, 35042 Rennes Cedex, France Cite this: Acc. Chem. Res. 1999, 32, 4, 311–323Publication Date (Web):December 18, 1998Publication History Received7 July 1998Published online18 December 1998Published inissue 20 April 1999https://doi.org/10.1021/ar980016iCopyright © 1999 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views3182Altmetric-Citations439LEARN 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 Read OnlinePDF (471 KB) Get e-AlertsSUBJECTS:Catalysts,Hydrocarbons,Ligands,Metals,Vinylidene group Get e-Alerts

Low dielectric loss polyethylene polymerized with chromocene catalyst

We studied the polymerization of ethylene monomers with chromocene catalyst to produce polyethylene with low dielectric loss in the microwave region. Chromocene (bis-cyclopentadienyl chromium) is very active for a long period during ethylene polymerization, and it also has a very low dipole moment because of its symmetrical molecular structure. Polyethylene polymerized by using chromocene has a low dielectric loss in the 500 MHz region caused by y relaxation. We were able to calculate the loss in this wavelength region from a summation of each individual contribution. The contributors included catalyst residue, and polar groups, i.e., methyl groups and double bonds such as vinyl, internal trans-vinylene, and vinylidene groups at a certain crystallinity. In order to make low dielectric loss polyethylene with a chromocene catalyst, we first tried to improve both the process of ethylene polymerization with a chromocene catalyst and the dielectric loss (tan δ) of polyethylene at 500 MHz. We measured the number of polar groups and the residual catalyst in polyethylene with the IR method. Our results revealed that both the hydrogenation reaction that occurs during ethylene polymerization with the chromocene catalyst and the crystallization of polyethylene after polymerization were very effective in reducing the dielectric loss of polyethylene.

A parametric study of the terminal maleation of polypropylene through an Alder Ene reaction

A study of the parameters that affect the Alder Ene reaction with respect to the synthesis of a terminally anhydride-functionalized polypropylene was carried out over a temperature range of 220–250°C using maleic anhydride concentrations of 2–12 mol equivalence with respect to the vinylidene group. As previously observed, a Lewis acid (i.e., SnCl2 · 2H2O) had a catalytic effect on the reaction at these temperatures, thereby improving anhydride content in the polymer for short reaction times. Increased temperature and maleic anhydride concentration had a positive effect on improving the incorporation of the succinyl anhydride moiety at the terminal site in polypropylene. Lower SnCl2 · 2H2O concentrations, likewise, improve the functionality of the product. The application of a second-order kinetic model to the measured succinyl anhydride results was not valid over the entire temperature range studied due to side reactions, particularly vinylidene isomerization, and homopolymerization of maleic anhydride. Ruthenium chloride has been examined as another possible catalyst candidate in the reaction and has been found to improve the level of anhydride incorporation in polypropylene compared to stannous chloride. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2371–2380, 1998

Novelty of Vinylidene-Terminated Polypropylene Prepared by a MgCl2-Supported TiCl4 Catalyst Combined with AlEt3 as Cocatalyst

Propene polymerization was conducted by a MgCl2/diisobutyl phthalate/TiCl4 catalyst combined with AlEt3 as cocatalyst. The polymerization was quenched by oxygen gas, and the polymer was fractionated into atactic and isotactic parts with boiling heptane. Each part was analyzed by 1H NMR. The spectra showed the resonances of vinylidene, vinyl, and hydroxymethylene groups, whose intensities were strongly dependent on the polymerization temperature and the stereoregularity. Raising the polymerization temperature increased the intensity of the hydroxymethylene group in both parts. The relative intensity of the hydroxymethylene to that of the vinylidene group was much higher in the atactic parts. These results suggest that the rates of β-hydrogen transfer and transfer by AlEt3 should be affected by the stereospecificity of the active species as well as polymerization conditions. Heat treatment at 120 °C in the presence of 1-octene quantitatively converted the terminal aluminum−carbon bond to a vinylidene group.

Evaluation of vinylidene group content in degraded polypropylene

Evaluation of vinylidene group content in degraded polypropylene

Kohlenwasserstoffverbrückte Metallkomplexe, XXXV. Addition von tert. Butylethinyl—pentacarbonyl—wolframat an π-koordinierte Kohlenwasserstoffe von kationischen Komplexen

Abstract The addition of the anionic alkynyl complex [(OC)5W-C⁡C-CMe3]−NEt4+ to unsaturated hydrocarbons of cationic complexes gives the thermolabile vinylidene bridged compounds (OC)5W=C=C(CMe3)(μ-hc)MLn [(μ-hc)MLn = (η1-C2H4)Re(CO)5 (1a), (η2-C3H5)Mo(η5-C5H5)(CO)(NO) (2), (η4-C6H4R)Fe(CO)3 (3a,b), (η4-C7H9)Fe(CO)3 (4a), (η5-C6H6)Mn(CO)3 (5a), (η6-C7H7)M(CO)3 M = Cr (6), W (7)]. At higher temperatures compounds 1a and 5a undergo elimination of the W(CO)5 fragment and 1,2 shift of the vinylidene group from the middle to the terminal C atom of the C⁡C-tBu group. The 1,4-cycloheptadienyl complex 4a isomerizes at temperatures above −30°C to give the 1,3-cycloheptadienyl derivative 4b which was characterized by X-ray diffraction.