- NEUARTIGE ALUMINACYCLOPENTADIENE MIT SPIRO-AT-STRUKTUR UND DEREN VERHALTEN GEGENUEBER NICKEL(0)- UND NICKEL(II)-VERBINDUNGEN
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Depending on the stoichiometry and solvent conditions aluminacycles III or IV are formed from the reaction of 1,2,3,4-tetraphenyl-1,4-dilithiumbutadiene (I) with AlCl3 (II) (see Scheme 1).It has beens shown that while IV undergoes intramolecular ionic complex formation to give IVa, III gives IIIa only to a smaller extent.III as well as IV take up two (COD)Ni0 units forming polynuclear complexes.The proposed structures are discussed.Both III and IV react with NiBr2 to give octaphenylcyclooctatetraene.In the presence of 1,2-bis(diphenylphosphino)ethane (DPPE) the complex DPPE-tetraphenylcyclobutadienenickel(0) can be isolated.
- Hoberg, Heinz,Richter, Wolfgang
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- DIPHOSPHAN-TETRAPHENYLNICKELACYCLOPENTADIEN
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Reaction of 1,2-bis(diorganophosphino)ethanenickel dibromide (I) with 1,2,3,4-tetraphenyl-1,4-dilithiumbutadiene (II) at -30 deg C yields diphosphannickelacyclopentadiene (III) which at elevated temperatures isomerizes to diphosphanecyclobutadienenickel(0) (IV).The thermodynamic and kinetic parameters of the rearrangement were determined.The structural and conformational analyses of III were carried out by means of 13C NMR, 31P NMR and Raman spectroscopy.The reactions of III and IV with CH3COOH, CO, RCCR and RN=C=NR have been examined and the observed reactivities III >> IV are discussed.
- Hoberg, Heinz,Richter, Wolfgang
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- Synthesis of octasubstituted cyclooctatetraenes and their use as electron transporters in organic light emitting diodes
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The synthesis and characterization of octasubstituted cyclooctatetraenes (COTs) as well as their use as electron transporting materials in organic LEDs are reported. Tetraaryl-tetraarylethynyl-cyclooctatetraenes [C8Ar4(C≡CAr)4/
- Lu, Ping,Hong, Haiping,Cai, Guoping,Djurovich, Peter,Weber, William P.,Thompson, Mark E.
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p. 7480 - 7486
(2007/10/03)
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- Reactivity of Titanium(II) Arene Derivatives with Substituted Alkynes. Cyclooligomerization Reactions and Crystal and Molecular Structure of 4-C4(C6H5)4>Ti2
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By treating Ti(η6-toluene)2 (X = Cl: 1a, X = Br: 1b) with C2R2 (R = Me, Ph) tetraorganylcyclobutadiene complexes of formula Ti(η4-C4R4)2 (R = Ph, X = Cl: 2a, X = Br: 2b; R = Me, X = Br: 3b) have been obtained in good yields.Compound 2b has been studied by X-ray diffraction methods.The titanium atom possesses an approximate square pyramidal coordination, the apical position being occupied by the symmetrically bonded tetraphenylcyclobutadiene ring, the four bridging bromides to the two AlBr2 groups forming the base of the pyramid, 0.99 Angstroem away from the titanium atom.The tetrabromoaluminato moiety of 2b can be substituted by carbocyclic anionic ligands, such as Cp and COT, and the corresponding complexes 4 and Ti(4h4-C4Ph4)(COT) were obtained.The spectroscopic study of the Ti(η6-benzene)2/diphenylacetylene (DPA) system (X = Cl: 5a, X = Br: 5b) has revealed the existence of three products, corresponding to the 1:1, 1:2, and 1:3 molar ratios.The possible role of the known AlX3 * C4R4 complexes in this reaction is discussed.The cyclotrimerization reactions of substituted acetylenes in the presence of η6-arene titanium(II) complexes as precursors have been studied.In toluene or methylcyclohexane Ti(η6-toluene)2 was found to catalyze the formation of alkyl-substituted aromatic hydrocarbons from 2-butyne, phenylacetylene, and 1-hexyne at about 80 deg C over 15 h with turnovers (moles of converted alkyne per mole titanium) of about 520, 900, and 990, respectively.The cyclooligomerization of DPA in the presence of Ti(η6-benzene)>(μ-X)2(AlX2)>2 (X = Cl, Br) was studied in detail.The activity of the chloro derivative 5a is higher than that of the bromide catalytic precursor 5b.In addition to hexaphenylbenzene and octaphenylcyclooctatetraene, other oligomerization by-products (triphenylethylene, 1,1,2,2-tetraphenylethane, 1,2,3-triphenylnaphthalene, and 1,2,3-triphenylazulene) were observed, whose formation was drastically reduced in the presence of alkyl aluminium halides. - Key Words: Titanium / Cyclooligomerization / Acetylenes, substituted / Tetraphenylcyclobutadiene, ligand
- Calderazzo, Fausto,Marchetti, Fabio,Pampaloni, Guido,Hiller, Wolfgang,Antropiusova, Helena,Mach, Karel
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p. 2229 - 2238
(2007/10/02)
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- ORGANIC CHEMISTRY OF SUBVALENT TRANSITION METAL COMPLEXES XI. OXIDATIVE ADDITIONS OF NICKEL(0) COMPLEXES TO CARBON-CARBON BONDS IN ALKYNES: NICKELIRENES AND NICKELOLES AS CATALYTIC CARRIERS IN THE OLIGOMERIZATION OF ALKYNES
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The formation of 2,3,4,5-tetraphenylnickelole-bis(triphenylphosphine) (IIIa) and 2,3,4,5-tetraphenylnickelole-bis(1,2-diphenylphosphino)ethane (IIIb), either from (E,E)-1,2,3,4-tetraphenyl-1,3-butadien-1,4-ylidenedilithium (I) and the corresponding nickel(II) chloride-phosphine complexes (II) or from the reduction of η4-tetraphenylcyclobutadienenickel(II) bromide dimer (XII) in the presence of phosphines, proceeds in good yields.Nickelole IIIa displays physical and chemical properties consistent with its structure and is a catalyst for the trimerization of diphenylacetylene.Nickelole IIIb is a highly associated structure but in its chemical response to alkynes, HOAc, O2, Br2, NaAlEt2H2 and heat displays the properties of a nickelole, rather than a cyclobutadienenickel(0) complex.Attempts to generate IIIb photochemically from η4-1,5-cyclooctadiene(η4-tetraphenylcyclopentadienone)nickel and diphos failed, but it was shown that structural types, such as η4-tetraphenylcyclopentadienone(diphos)nickel (a model for the structure suggested by Hoberg and Richter for IIIb), are unstable.Oligomerizations of diphenylacetylene by bis(1,5-cyclooctadiene)nickel were retarded by conducting the reaction in THF or in the presence of diphos.This retardation permitted the interception of products (cis-stilbene and (E,E)-1,2,3,4-tetraphenyl-1,3-butadiene)diagnostic for the intermediacy of nickelirenes and nickeloles.Deuterium labeling verified the presence of carbo-nickel bonds.These trapping experiments, together with findings on the thermal behavior of nickeloles, are combined into a comprehensive view of the cyclotrimerization, cyclotetramerization and linear polymerization of alkynes by nickel(0).
- Eisch, John J.,Galle, James E.,Aradi, Allen A.,Boleslawski, Marek P.
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p. 399 - 416
(2007/10/02)
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- Oxidative Addition of Nickel(0) Complexes to Carbon-Carbon Bonds in Cyclobutadiene. The Question of the Interconvertibility of Cyclobutadiene-nickel(0) Complexes and the Nickelaring Systems
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Bis(triethylphosphine)(η4-tetraphenylcyclobutadiene)nickel (4) was synthesized by the reduction of (η4-tetraphenylcyclobutadiene)nickel(II)bromide (3) with t-butyllithium in the presence of Et3P, and its structure was determined by X-ray crystallography.Furthermore, its reactivity towards CO, CH3CO2H, PhCCPh, LiAlH4 and O2 were investigated. 1,1-Bis(triethylphosphine)-2,3,4,5-tetraphenylnickelole (14) was synthesized from (E,E)-1,4-dilithio-1,2,3,4-tetraphenyl-1,3-butadiene (15) and bis(triethylphosphine)nickel(II)bromide.Since the resulting crystals of the nickelole were not suitable for X-ray structure determination, the compound was characterized by elemental analyses, spectral data and carbonylation to yield tetraphenylcyclopentadienone (6).Analogous reductions of (η4-tetraphenylcyclobutadiene)nickel(II)bromide (3) in the presence of Ph3P or Ph2PCH2CH2PPh2, followed by carbonylation, led to 6 in 40percent yield, demonstrating that about half of the cyclobutadiene rings in 3 undergo cleavage upon reduction to give the nickelole.Reactions of the dilithium reagent 15 with NiBr2 complexed with Me2PCH2CH2PMe2, Ph3P or Et2PCH2CH2PEt2, led to the formation of thermolabile nickeloles, as demonstrated by carbonylation which yielded 6.Warming of the nickeloles and subsequent treatment with CH3CO2H led to the formation of 1,2,3,4,5,6,7,8-octaphenyl-1,3,5,7-octatetraene (8) and, in one case, octahenylcyclooctatetraene (5).The relevance of these findings to the mechanism of the Reppe nickel-catalyzed oligomerization of alkynes is discussed. - Key words: Insertion Reaction, Oxidative Addition, Cyclobutadiene-Nickel(0) Complexes, Nickelacyclopentadiene, Nickelole
- Eisch, John J.,Piotrowski, Andrzej M.,Aradi, Allen A.,Krueger, Carl,Romao, Maria J.
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p. 624 - 635
(2007/10/02)
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