- Formation of metallaboranes from the group IV transition metals and pentaborane(9): Crystal and molecular structure of [(Cp2Zr)2B5H8] [B11H14]
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The reactions between [(C5H5)2MCl2] (where M = Ti, Zr, Hf) and Li[B5H8] in a variety of solvents have been investigated. In the case of Zr, a pale orange solid, μ-(Cp2ClZr)B5H8 (1), is formed in 70% yield. Compound 1 exists as a B5H9 cage with a Cp2ClZr moiety replacing a bridging H atom. The variable temperature NMR spectra of 1 reveal two fluxional processes, one (ΔG? = 54 kJ mol-1) which renders a plane of symmetry in the molecule and a higher temperature one (ΔG? = 48 kJ mol-1) which renders all the basal B atoms equivalent. Dynamic processes are suggested to account for these observations. Passage of a CH2Cl2 solution of 1 through silica gel affords 2, [(Cp2Zr)2B5H8] [B11H14], a yellow, air-stable, crystalline solid, in 14% yield. The cation in 2, [(Cp2Zr)2B5H8]+, consists of a distorted spiro[2.2]pentane-like B5 moiety comprising two B3 triangles sharing a naked boron vertex. The two triangles are twisted 73° with respect to each other, and the two [Cp2Zr] groups bond in a trihapto arrangement to the two opposite B-B-B edges. Each exterior B-Zr edge is H-bridged, and the B atoms possess terminal hydrogens. Reactions of Cp2HfCl2 with Li[B5H8 lead to the formation of the analogue of 2, [(Cp2Hf)2B5H8] [B11H14] (3). The precursor to 3, that is, the Hf analogue of 1, is not observed. Reaction between Li[B5H8] and Cp2TiCl2 afforded no identifiable products, but reaction with CpTiCl3 resulted in cage coupling and the formation of B1OH14.
- Thomas, Rhodri Ll.,Rath, Nigam P.,Barton, Lawrence
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- Die Bildung von β-C-H agotischen Alkenylzirconocen-Komplexen bei der anormalen Hydrozirconierung von Alkinen
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Some alkynes R1CCR2 bearing bulky substituents undergo abnormal hydrozirconation reactions when treated with the reagent x (1).The products obtained do not contain newly formed C-H bonds.Dicyclopentadienylzirconacyclopentadiene systems (5) are formed instead.Extended Hueckel calculations as well as the isolation of the product (3b) in addition to Cp2ZrCl2 and (5b) from Me3SiCCPh and 1 indicate that β-C-H agostic alkenylmetallocene complexes may serve as important intermediates for this variant of hydrozirconation.The molecular structure of 3b was deterrmined by an X-ray diffraction study.Complex 3b crystallizes in space group P21/n with cell constants a 9.641(2), b 18.066(3), c 11.762(1) Angstroem, β= 92.122(7) deg, Z=4.The Zr-C(1)-C(2) angle is 89.9 deg and the Zr-H(2) distance is 2.29(2) Angstroem.
- Erker, Gerhard,Zwettler, Roland,Krueger, Carl,Schlund, Rueger,Hyla-Kryspin, Isabella,Gleiter, Rolf
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- Highly fluorescent benzophosphole oxide block-copolymer micelles
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The efficient synthesis of highly fluorescent para-biphenyl-substituted benzophospholes via zirconium-mediated metallacycle transfer is reported. A norbornene-appended benzophosphole oxide monomer was found to readily undergo living ring-opening metathesis polymerization with the Grubbs third-generation catalyst to yield either a homopolymer or block copolymers. The resulting block copolymers consisting of lipophilic alkylated- or pinacolboronate-capped comonomers undergo self-assembly into spherical micelles in tetrahydrofuran/hexanes mixtures, as determined by dynamic light scattering and transmission electron microscopy. One hallmark of the benzophosphole-containing polymers is their greatly enhanced emission intensity in solution in relation to their monomers, presumably due to a restriction in molecular motion upon formation of homopolymers or assembled block-copolymer micelles. Evidence for "analyte amplified precipitation" was found, wherein addition of a substoichiometric amount of fluoride to a benzophosphole oxide-pinacolboronate block-copolymer spherical micelle leads to rapid precipitation of highly emissive aggregates. This observation should guide the development of related methods to visually detect (and sequester) analytes in solution.
- Parke, Sarah M.,Tanaka, Susumu,Yu, Haoyang,Hupf, Emanuel,Ferguson, Michael J.,Zhou, Yuqiao,Naka, Kensuke,Rivard, Eric
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- REACTIONS OF Cp2M(CO)2 AND Cp2M(CO)(PPh3) (M=Zr, Hf) WITH ACETYLENES: FORMATION OF SOME METALLACYCLOPENTADIENE COMPLEXES OF ZIRCONOCENE AND HAFNOCENE
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The photolysis of Cp2Zr(CO)2 with diphenylacetylene or 3-hexyne yields, the respective zirconacyclopentadiene complexes Cp2Zr(C4R4) (R=Ph, Et).The thermolysis of Cp2Zr(CO)2 with 3-hexyne or bis(pentafluorophenyl)acetylene also leads to the formation of Cp2Zr(C4R4) (R=Et, C6H5).HCl degradation of Cp2Zr yields 1,2,3,4-tetrakis(pentafluorophenyl)-1,3-butadiene and Cp2ZrCl2.When Cp2Zr(CO)2 is heated with diphenylacetylene in a closed vessel, tetraphenylcyclopentadienone is formed along with Cp2Zr(C4Ph4).The hafnacyclopentadiene complexes Cp2Hf(C4R4) (R=Ph, C6G5, Et) are obtained when Cp2Hf(CO)2 is thermolyzed with the respective acetylene in refluxing octane.Complexes Cp2Hf(C4R4) (R=Ph, Et) are also formed when Cp2Hf(CO)2 is photolyzed with diphenylacetylene or 3-hexyne, respectively.The monocarbonyl-triphenylphosphine complexes Cp2M(CO)(PPh3) (M=Zr, Hf) can be prepared via the irradiation of hydrocarbon solutions of Cp2M(CO)2 and triphenylphosphine.These complexes react readily with diphenylacetylene and 3-hexyne at 55-60 deg C to afford the corresponding metallacyclopentadiene complexes Cp2M(C4R4) (M=Zr, Hf; R=Ph, Et).The metallocene dicarbonyls Cp2M(CO)2 (M=Zr, Hf) are readily prepared via the reduction of Cp2MCl2 (M=Zr, Hf) with amalgamated magnesium metal in THF solution under one atmosphere of carbon monoxide.
- Sikora, David J.,Rausch, Marvin D.
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- PREPARATION AND PROPERTIES OF (η-C5H5)2 ZrCl AND (η-C5H5)2Zr2; TRIMETHYLSILYL GROUP TRANSFER FROM MERCURY TO ZIRCONIUM
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Two silyl-zirconium compounds (η-C5H5)2ZrCl (I) and (η-C5H5)2-Zr2 (II), have been prepared by the reaction of η(C5H5)2ZrCl2 with Hg2 in refluxing benzene.While I is unreactive toward 1-hexyne (55-60 deg C) and CO (350 psi), t
- Blakeney, A. J.,Gladysz, J. A.
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- Metalations with group 4 alkylmetal(IV) halides: Expeditious route to metallocene and nonmetallocene procatalysts
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Group 4 alkylmetal(IV) halides of the type Bu2MtCl2, generated in hydrocarbon media at -78°C by treating MtCl4 with 2 equiv of n-butyllithium, function as strong bases toward a variety of Br?nsted acids, E-H, where E = cyclopentadienyl or substituted cyclopentadienyl, 1-alkynyl, indenyl, alkoxy, aryloxy, and disubstituted amino, to form metallocene and nonmetallocene procatalysts, E2MCl2, expeditiously and generally in high yield.
- Eisch, John J.,Owuor, Fredrick A.,Otieno, Peter O.
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- Insertion of sodium phosphaethynolate, Na[OCP], into a zirconium-benzyne complex
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Reaction of the zirconium-benzyne complex [Cp2Zr(PMe3)(C6H4)] with sodium phosphaethynolate, Na[OCP], affords a zircono-phosphaalkene complex. Notably, unlike reactions of other transition metal complexes with Na[OCP] that yield the products of simple salt metathesis, this transformation represents novel Na[OCP] insertion chemistry and formation of an unusual solid state coordination polymer. The polymer is disrupted upon addition of Me3SiCl to afford a silyl-capped dimer that retains the zirconophosphaalkene functionality. Protonation of either form of zirconophosphaalkenes results in the formation of benzoylphosphine, PhC(O)PH2.
- Kieser, Jerod M.,Gilliard, Robert J.,Rheingold, Arnold L.,Grützmacher, Hansj?rg,Protasiewicz, John D.
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- Carbon-carbon bond formation reaction of zirconacyclopentadienes with alkynes in the presence of Ni(II)-complexes
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Zirconacyclopentadienes, prepared from two alkynes or a diyne, reacted with the alkyl-, trimethylsilyl-, or alkoxy-substituted third alkyne as well as an alkyne with an electron-withdrawing group in the presence of a stoichiometric amount of NiBr2(PPh3)2 to give benzene derivatives in good yields. Heteroatom-containing diynes such as dipropargylbenzylamine and propargyl-homopropargylbenzylamine gave isoindoline and tetrahydroisoquinoline derivatives in good to high yields. This procedure was also used for the selective preparation of benzene derivatives from three different alkynes. The use of trimethylsilyl-substituted alkyne as the first, second or third alkyne afforded desilylated benzene derivatives. The reaction of zirconacyclopentadienes with allenes gave benzene derivatives as a mixture of two isomers.
- Takahashi, Tamotsu,Tsai, Fu-Yu,Li, Yanzhong,Nakajima, Kiyohiko,Kotora, Martin
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- Investigation of the mechanism of alkane reductive elimination and skeletal isomerization in Tp′Rh(CNneopentyl)(R)H complexes: The role of alkane complexes
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Experiments are described that provide indirect evidence for the involvement of alkane σ-complexes in oxidative addition/reductive elimination reactions of Tp′Rh(L)(R)H complexes (Tp′ = tris-3,5-dimethylpyrazolylborate, L = CNCH2CMe3). Reductive elimination rates in benzene-d6 were determined for loss of alkane from Tp′Rh(L)(R)H, where R = methyl, ethyl, propyl, butyl, pentyl, and hexyl, to generate RH and Tp′Rh(L)(C6D5)D. The isopropyl hydride complex Tp′Rh(L)(CHMe2)H was found to rearrange to the n-propyl hydride complex Tp′Rh(L)(CH2CH2CH3)H in an intramolecular reaction. The sec-butyl complex behaves similarly. These same reactions were studied by preparing the corresponding metal deuteride complexes, Tp′Rh(L)(R)D, and the scrambling of the deuterium label into the α- and ω-positions of the alkyl group monitored by 2H NMR spectroscopy. Inverse isotope effects observed in reductive elimination are shown to be the result of an inverse equilibrium isotope effect between the alkyl hydride(deuteride) complex and the σ-alkane complex. A kinetic model has been proposed using alkane complexes as intermediates and the selectivities available to these alkane complexes have been determined by kinetic modeling of the deuterium scrambling reactions.
- Northcutt,Wick,Vetter,Jones
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- Heterometallic (ZrIII)2-Al hydrides [(Cp 2Zr)2(μ-H)](μ-H)2AlX2 (X = Cl or Br): Preparative synthesis and reactivity. Molecular structure of [(Cp 2Zr)2(μ-Cl)](μ-H)
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A procedure was developed for the synthesis of trinuclear cyclic (Zr III)2-Al hydrides [(Cp2Zr)2(μ-H)] (μ-H)2AlX2 (X = Cl (1a) or Br (1b)). These complexes were prepared in 60-65% yields by
- Sizov,Zvukova,Khvostov,Gorkovskii,Starikova,Bulychev
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- Die Reaktivitaetsabstufung von Trimethylsiloxygruppen gegenueber dem Hydrozirconierungsreagenz Cp2Zr(H)Cl
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The trimethylsilylethers of unsaturated alcohols yield different compounds on reaction with Cp2Zr(H)Cl (1) depending on the length and branching of the alkenyl chain.With the hex-1-en-6-ol derivative the usual product of hydrozirconation is obtained in high yield.The reaction of the silylated 3-methyl-but-1-en-3-ol (11) is however, accompanied by hydrogenation of the Si-O bond.The main products are trimethylsilane and the yellow complex Cp2Zr(Cl)CH2CH2C(CH3)2OZr(Cl)Cp2 (12).The molar ratio of the reactants determines the final products of the reaction of allyl trimethylsilyl ethers 3 and 1.An equimolar preparation yields mainly the usual product of hydrozirconation, whereas an excess of 1 favours the formation of a binuclear five-membered chelate (5) and trimethylsilane.CO inserts readily into the Zr-C bond of 12, but 5 does not react with CO.The binuclear structure of 12 was established by an X-ray diffraction study.The character of the Zr-O and Zr-C bonds is discussed in terms of these results.
- Uhlig, E.,Buerglen, B.,Krueger, C.,Betz, P.
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- Electrochemical reduction of zirconocene dihalides and dialkyls studied by electron spin resonance
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An electrochemical cell designed to work in the cavity of an ESR spectrometer at variable temperatures was used to study the electrochemical reduction of zirconocene compounds Cp2ZrX2 (X = halogen (hal); Cp = η5-C5/s
- Samuel, Edmond,Query, Dominique,Vedel, Jacques,Basile, Fran?oise
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- Formation of linear tetramers of diarylalkynes by the Zr/Cr system
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The reaction of diarylalkynes with Cp2ZrBu2 and successive treatment with CrCl3 afforded linear tetramers of diarylalkynes, (1E,3E,5E,7E)-octatetraenes. On the other hand, dialkylalkynes did not give the corresponding octatetraenes but cyclized products, such as pyridines and pyridones, by the reaction with nitriles and isocyanates. Copyright
- Takahashi, Tamotsu,Liu, Yuanhong,Iesato, Atsushi,Chaki, Shinji,Nakajima, Kiyohiko,Kanno, Ken-Ichiro
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- Synthesis and catalytic activity of group 4 metallocene containing silsesquioxanes bearing functionalized silyl groups
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A series of metallocene-containing silsesquioxanes with alkenylsilyl and trimethylsilyl groups, Cp′2M[(c-C5H 9)7Si7O11](OSiMe2R) (2b-d, 3b-d, 4d, 5d: Cp′ = Cp (cyclopentadienyl), Cp* (pentamethylcyclopentadienyl); M = Ti, Zr, Hf, R = methyl, vinyl, allyl), have been synthesized. The structures of the complexes Cp2M[(c-C 5H9)7Si7O11](OSiMe 2CH2CH=CH2) (M = Zr (3d), Hf (5d)) have been unambiguously established by single-crystal X-ray diffraction analyses. Silylation or germylation of the zirconocene-containing silsesquioxane monosilanol Cp2Zr[(c-C5H9)7Si 7O11](OH) (3a) or its hafnocene derivative Cp 2Hf[(c-C5H9)7-Si7O 11](OH) (5a), which can be prepared by the careful reaction of the silsesquioxane trisilanol (c-C5H9)7Si 7O9(OH)3 (1a) with zirconocene dichloride or hafnocene dichloride, yields the new series of metallocene-containing silsesquioxanes Cp2Zr[(c-C5H9) 7Si7O11](OSiMe2H) (3e), Cp 2-Zr[(c-C5H9)7Si7O 11](OGeMe3) (3f), and Cp2Hf[(c-C 5H9)7Si7O11](OSiMe 2H) (5e). The reaction of 3e with 2 equiv of hydrogen chloride results in the formation of the dimethylsilyl-containing silsesquioxane disilanol (c-C5H9)7Si7O 9(OH)2(OSiMe2H) (1e), indicating the applicability of metallocene moieties as protecting groups of two adjacent silanol groups. Silsesquioxanes bearing alkenylsilyl groups can be easily converted to derivatives with ethoxysilyl groups, Cp2M[(c-C 5H9)7Si7O11] [OSiMe 2(CH2)3SiMe2(OEt)] (M = Ti (2g), Zr (3g)), by the hydrosilylative reaction. The preliminary examination of the catalytic activity of these metallocene-containing silsesquioxanes toward the epoxidation of cyclohexene by tert-butyl hydroperoxide revealed that titanocene-containing silsesquioxanes (2b-d) show modest catalytic activity. The presence of alkenylsilyl groups has been found to accelerate the reactions, especially in the case of titanium-bridged silsesquioxanes.
- Wada, Kenji,Itayama, Naohiko,Watanabe, Naoki,Bundo, Masaki,Kondo, Teruyuki,Mitsudo, Take-Aki
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- Novel dimeric ring systems containing gallium
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A gallole (gallacyclopentadiene) is found to dimerise in a different fashion than boroles; the corresponding diazabutadiene complex is also dimeric.
- Cowley, Alan H.,Brown, David S.,Decken, Andreas,Kamepalli, Smuruthi
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- REAKTIONEN VON BIS(η-CYCLOPENTADIENYL)ZIRCONIUMHYDRIDEN MIT (IMINOACYL)ZIRCONOCEN-KOMPLEXEN
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The reaction of imidoylzirconocene complexes with zirconocene hydrides yields (N-alkylamido)zirconocene complexes.For a mechanistic study, the specifically substituted imidoylzirconocene complexes 3b-3d have been prepared and treated with the oligomeric m
- Froemberg, Wolfgang,Erker, Gerhard
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- 1H and 13C NMR evidence for the intermediate species 1:η5-C5H4)>2. Cyclopentadienyl C-H bond activation by thermolysis of n, Cp2Zr(R)Cl, and 2
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Thermal decomposition at 80 deg C of n (1) (Cp = η5-C5H5), Cp2Zr(R)Cl (2b) (R = cyclohexyl) and (Cp2ZrCl)2 gives the fulvalenide dizirconium complex 5 : η5-C5H4-C5H4)> (4) via the intermediate 1 : η5-C5H4)>2 (5).Complex (5) can also be prepared by treating Cp2ZrCl2 with sodium amalgam (1.5 eq) in refluxing toluene.In the presence of cyclic polyenes, such as 1,5-cyclooctadiene (1,5-COD) thermolysis of 1 takes place at room temperature probably to give initially a labile ? allyl species, which can be formulated in the case of the reaction with 1,5-COD as Cp2Zr(η3-C8H11)Cl.This is the first example in zirconium(IV) chemistry of cyclopentadienyl C-H bond activation resulting in hydrogenation of unsaturated substrates.
- Choukroun, Robert,Raoult, Yveline,Gervais, Daniele
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- Selective tin-carbon bond cleavage reactions of trimethylstannylzirconocene dichloride with electrophiles
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The reaction of 5,5-bis(trimethylstannyl)cyclopentadiene with CpZrCl3 (Cp = η5-C5H5) affords the monostan-nylated metallocene complex (η5-Me3SnC5H4)CpZrCl2 (1), accompanied by variable amounts of (η5-ClMe2-SnC5H4)CpZrCl2 (2). The complex (1) reacts with BCl3 or with ICl to afford 2 (Sn-CH3 cleavage), but with HCl, Cp2ZrCl2 is obtained instead (Sn-Cp cleavage). Depending on the reaction conditions, treatment of either 1 or 2 with BBr3 affords (η5-BrMe2SnC5H4)CpZrBr2 (3) or (η5-Br2MeSnC5H4)CpZrBr2 (4). The reaction of 1 with excess I2 affords the iodostannylated complex (η5-IMe2SnC5H4)CpZrCl2 (5). Two of the complexes (2·2C6H5CH3 and 4·THF) are crystallographically characterized. The adduct 4·THF has a distorted trigonal bipyramidal geometry about tin with a long O-Sn distance of 2.655 A. We find overall that Me3Sn substituents undergo electrophilic halodemethylation much more readily than corresponding Me3Si substituents, whereas the reactivities of the halostannylated complexes toward nucleophiles such as airborne moisture are much lower than those of their halosilylated counterparts.
- Cheng,Slebodnick,Deck,Billodeaux,Fronczek
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- Synthesis of Me2> (tmeda = tetramethylethylenediamine) and of a Binuclear Zirconocene Phosphine Functionalized Ketene Complex, (Both Structurally Characterized), the Latter via Carbonylation of ''
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Reaction of Me2>, (1), (tmeda = tetramethylethylenediamine) with in tetrahydrofuran at - 78 deg C yields 2-n>, n = 1, (2), or n = 2, (3); carbonylation of (2) affords exclusively a novel binuclear ketene complex, , (4), which in the crystal form possesses a Zr-P linkage .
- Engelhardt, Lutz M.,Jacobsen, Geraldine E.,Raston, Colin L.,White, Allan H.
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- FUNKTIONELLE TRIMETHYLPHOSPHANDERIVATE. XIX. PHOSPHINOMETHYLSUBSTITUIERTE ZIRCONIUMVERBINDUNGEN ALS NUCLEOPHILE: SYNTHESE, REAKTION MIT CO UND MOLEKUELSTRUKTUR VON 2Ni
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The organozirconium-substituted phosphines Cp2Zr(X)CH2PMe2 (Cp = η5-C5H5; X = Cl, CH2PMe2) have been prepared from Cp2ZrCl2 and LiCH2PMe2.In these compounds, the phosphinomethyl group acts as a monohapto (η1-) ligand.On reaction with CO, the bis(phosphinomethyl)zirconium complex forms a red complex, which by means of NMR spectroscopy is shown to contain a novel zircona heterocycle.With Ni(COD)2, Cp2Zr(CH2PMe2)2 forms the 2:1 complex 2Ni.Crystals (from tetrahydrofuran) are triclinic, space group P, with parameters a 13.433(5), b 18.062(3), c 19.505(2) Angstroem, α 64.35(2), β 76.82(1), γ 71.28(2) deg, V 4018.12 Angstroem3, dx 1.445 g cm-3 for Z = 4, μ(Mo-Kα) 11.5 cm-1, T 21 deg C.Refinement of 743 parameters on 8826 reflections converged at R = 0.055.The molecular structure consists of monomeric units with two bidentate Cp2Zr(CH2PMe2)2 molecules acting as chelating ligands to a tetrahedral Ni0 centre.The six-membered Zr(CH2PMe2)2Ni rings adopt a chair conformation.Steric strain by interaction of the axial cyclopentadienyl and methyl ligands at Zr and P, respectively, causes these rings to be considerably flattened.
- Karsch, Hans H.,Mueller, Gerhard,Krueger, Carl
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- The tetracyclopentadienyls of titanium, zirconium and hafnium: New synthetic procedures and reactivity
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In toluene as medium, the tetra(cyclopentadienyl) derivatives of Group 4 elements, MCp4 (M=Ti, Zr, Hf), have been prepared in high yields from MCp2Cl2 and NaCp. The reactivity of ZrCp4 with species containing active protons such as Ph3SiOH or strong acids has been studied. Substituted bis(cyclopentadienyl) derivatives were produced except in the case of the reaction between ZrCp4 and CF3SO3H. In this case, the tris(cyclopentadienyl) derivative ZrCp3(CF3SO3) was obtained as a pale yellow crystalline material, reactive with water to give the μ-oxo derivative of zirconium(IV), [ZrCp2(CF3SO3)]2O, which has been characterized by standard methods and by X-ray diffraction. Crystal data: C22H20F6O7S2Zr2, M=756.96 g mol-1, monoclinic, space group C2/c (no. 15), a=19.525(4), b=9.028(2), c=16.152(5) A, β=107.31(2)°, V=2718.2(1) A3, Z=4, dcalc=1.850 g cm-3, λ(Cu-Kα)=1.54184 A, T=291 K, μ=85.66 cm-1, F(000)=1496, R=0.054, Rw=0.049.
- Calderazzo, Fausto,Englert, Ulli,Pampaloni, Guido,Tripepi, Giovanna
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- Nanoparticle supported bis (cyclopentadienyl) zirconium dichloride catalysts for styrene polymerization
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Heterogeneous nanoparticle NA-MgO-MAO/NA-TiO2 (anatase)-MAO supported bis (cyclopentadienyl) zirconium dichloride (Cp2ZrCl 2) are synthesized and used for the polymerization of styrene monomer. The supporting process is co
- Kantam, Mannepalli L.,Ghosh, Sutapa,Aziz, Khathija,Sreedhar,Choudary, Boyapati M.
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- Nucleophilic reactivity of 1-zirconacyclopent-3-ynes: Carbon-carbon bond formation with aldehydes
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Nucleophilic reactions of 1,1-bis(η5-cyclopentadienyl)-1-zirconacyclopent-3-yne (1) with proton and aldehydes were studied. The reaction with HCl gave a mixture of 2-butyne and 1,2-butadiene. Complex 1 reacted with benzaldehyde to give 1-phenyl-2-methyl-2,3-butadien-1-ol (3) in moderate yields in the presence of a proton source such as triethylammonium hydrochloride, while it gave 2-methylene-1-phenyl-3-buten-1-ol (4) on using triethylammonium tetraphenylborate.
- Suzuki, Noriyuki,Watanabe, Takaaki,Hirose, Takuji,Chihara, Teiji
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- Thermal Isomerization of the Buchwald Seven-Membered Zirconacyclocumulene and Its Interaction with Acetylenes. Synthesis and Structures of Novel Seven-Membered Zirconacyclocumulene Complexes
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(Chemical Equation Presented) On prolonged heating of the Buchwald seven-membered zirconacyclocumulene Cp2Zr[η4-Me3SiC4(SiMe3)-C(C2SiMe3)=CSiMe3] (1) in toluene at 100°C, the isomerization of 1 takes place with the formation of a seven-membered zirconacyclocumulene complex, Cp2Zr[η4-Me3SiC4(SiMe3)-C(SiMe3)=C(C2SiMe3)] (8), containing the Me3SiC≡C group in α-position and the SiMe3 group in β-position with respect to the Zr atom. A remarkable peculiarity of complex 8 is its ability to undergo a rapid degenerate rearrangement at room temperature in toluene solution, as a result of which only two rather than four singlets of the Me3Si groups are observed in the 1H NMR spectrum of 8 under such conditions. At temperatures below 200 K, the rate of this rearrangement decreases and, as a consequence, the 1H NMR spectrum of 8 acquires the normal view. If 1 is heated at 100 C in the presence of acetylenes such as 1,4-bis(tert-butyl)butadiyne (tBuC≡C-Ci≡CtBu) and tolane, the corresponding seven-membered zirconacyclocumulenes, viz., Cp2Zr[η4-tBuC4(tBu)-C(C2SiMe3)=CSiMe3] (7) and Cp2Zr[η4-Me3SiC4(SiMe3)-C(Ph)=CPh] (14), are formed along with free Me3SiC≡C-C≡CSiMe3. The interaction of 1 with 1,4-diphenylbutadiyne (PhC≡C-C≡CPh) at 100°C leads to the formation of a mixture of products, from which a zirconacyclopentadiene metallacycle, Cp2Zr[η2-PhC=C(C2Ph)-C(C2Ph)=CPh] (10), as well as seven-membered zirconacyclocumulenes Cp2Zr[η4-PhC4(Ph)-C(C2SiMe3)=CSiMe3] (11), Cp2Zr[η4-Me3SiC4(SiMe3)-C(C2Ph)=CPh] (12), and Cp2Zr[η4-PhC4(Ph)-C(C2Ph)=CPh] (13) were isolated. The structures of 8, 9, 10, 12, and 14 have been established by X-ray crystallography. The mechanism of the reactions found is discussed.
- Burlakov, Vladimir V.,Bogdanov, Vyacheslav S.,Arndt, Perdita,Baumann, Wolfgang,Spannenberg, Anke,Lyssenko, Konstantin A.,Ananyev, Ivan V.,Rosenthal, Uwe,Shur, Vladimir B.
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- HYDROZIRCONIERUNG VON NITRILEN: DIE BILDUNG EIN- UND ZWEIKERNIGER (ALKYLIDENAMIDO)ZIRCONOCEN-KOMPLEXE
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Cp2Zr(-N=CHR)Cl compounds (9a-9c: R=CH3, C6H5, CH2Ph, respectively) are formed upon hydrozirconation of nitriles.Subsequent reaction with an aryllithium reagent yields Cp2Zr(-N=CHR)Ar (14).The (alkylidene amido)zirconocene complexes are characterized by a
- Froemberg, Wolfgang,Erker, Gerhard
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- A new route to early-late heterobimetallic μ-alkylidene complexes
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The reaction of two equivalents of Cp2ZrHCl (1) with Cp(CO)2Re=CHR (2, R = CH2CH2CMe3; 4, R = CH3) led to the formation of the heterobimetallic μ-alkylidene complexes Cp2Zr(μ-CHR)(μ,η1,η2-CO)Re(CO)Cp (3, R = CH2CH2CMe3; 5, R = CH3).
- Casey, Charles P.,Askham, Frederic R.,Petrovich, Lori M.
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- SYNTHESIS AND CHEMICAL PROPERTIES OF DICYCLOPENTADIENYLZIRCONIUM BIS(DIPHENYLARSENIDE) AND BIS(DIPHENYLANTIMONIDE), (E = As OR Sb)
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Treatment of Cp2ZrCl2 (Cp = η-C5H5) with LiEPh2 (E = As or Sb) affords the corresponding pentelide complexes Cp2Zr(EPh2)2.In the particular case of the Cp2TiCl2/LiAsPh2 system there is evidence for reduction to Cp2TiAsPh2.The spectral and elemental charac
- Wade, Steven R.,Wallbridge, Malcolm G. H.,Willey, Gerald R.
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- CARBENE COMPLEXES OF ZIRCONIUM. SYNTHESIS, STRUCTURE, AND REACTIVITY WITH CARBON MONOXIDE TO AFFORD COORDINATED KETENE
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Treatment of Cp2Zr(L)(CO) (Cp=C2H5; L=PMe3, CO) with Cp*2ZrH2 (Cp*=C5Me5) afford zirconium oxycarbene complexes, Cp2(L)Zr=CHO-Zr(X)Cp*2 (L=PMe3, X=H, I; L=CO, X=H), that represent some of the first examples of group 4 metal-to-carbon multiple bonding.The first X-ray diffraction structure determination of a zirconium carbene complex, that of Cp(PMe3)Zr=CHO-Zr(I)Cp*2.C6H6, is reported (C2/c, a=27.318(4) Angstroem, b=19.985(3) Angstroem, c=19.932(5) Angstroem β=132.188(10) deg, Z=8) and shows a very short Zr-C bond length of 2.117 (7) Angstroem.Treatment of Cp2(CO)Zr=CHO-Zr(H)Cp*2 with CH3I or Cp2(PMe3)Zr=CHO-Zr(I)Cp*2 with CO affords the zirconium substituted enediolate zirconacycle, , which has been characterized by an X-ray diffraction study (P21/c, a=15.866(4) Angstroem, b=10.673(3) Angstroem, c=20.561(4) Angstroem, β=105.5(2) deg, Z=4).It is proposed that this complex forms by coupling of the zirconoxycarbene and a carbonyl to give a metal-coordinated ketene intermediate that subsequently rearranges to the isolated product.An isotopic crossover experiment has demonstrated that the new carbon-carbon bond is formed in an intramolecular coupling step.The ketene intermediate can be trapped by dissolving Cp2(CO)Zr=CHO-Zr(H)Cp*2 in pyridine, giving Cp2(py)Zr(O=C=CHOZr(H)Cp*2).Treatment of the isolated ketene complex with CH3I in benzene gives the enediolate zirconocycle; in pyridine Cp2(py)Zr(O=C=CHOZr(I)Cp*2) can be observed spectroscopically.
- Barger, Paul T.,Santarsiero, Bernard D.,Armantrout, Justine,Bercaw, John E.
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- Four homologous zirconium 2,2′-biphenyldiyls: Synthesis, structure, and reactivity
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A homologous family of zirconohydrocarbons bearing the 2,2′-biphenyldiyl ligand (biphe) has been prepared. One of the homologues is a tetraanionic zirconate, two are examples of homoleptic σ-bound zirconohydrocarbons, and three are anionic ate complexes.
- Hilton, Cameron L.,King, Benjamin T.
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- Low-spin 1,1′-diphosphametallocenates of chromium and iron
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We report two anionic diphosphametallocenates, [K(2.2.2-crypt)][M(PC4Me4)2] (M = Cr, 2-Cr; Fe, 2-Fe). Both are low-spin (S = ?) by EPR spectroscopy and SQUID magnetometry. This contrasts the high-spin (S = ) ferrocenate, [K(2.2.2-crypt)][Fe(C5H2-1,2,4-tBu)2] (4-Fe). Quantum chemical calculations suggest this is due to significant differences in ligand field splitting of the d-orbitals which also explain structural features in the 2-M complexes. This journal is
- Greer, Samuel M.,üngor, ?kten,Beattie, Ross J.,Kiplinger, Jaqueline L.,Scott, Brian L.,Stein, Benjamin W.,Goodwin, Conrad A. P.
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p. 595 - 598
(2021/01/29)
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- Palladium-Catalyzed Reductive Coupling Reaction of Terminal Alkynes with Aryl Iodides Utilizing Hafnocene Difluoride as a Hafnium Hydride Precursor Leading to trans-Alkenes
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Herein, we describe a reductive cross-coupling of alkynes and aryl iodides by using a novel catalytic system composed of a catalytic amount of palladium dichloride and a promoter precursor, hafnocene difluoride (Cp2HfF2, Cp=cyclopentadienyl anion), in the presence of a mild reducing reagent, a hydrosilane, leading to a one-pot preparation of trans-alkenes. In this process, a series of coupling reactions efficiently proceeds through the following three steps: (i) an initial formation of hafnocene hydride from hafnocene difluoride and the hydrosilane, (ii) a subsequent hydrohafnation toward alkynes, and (iii) a final transmetalation of the alkenyl hafnium species to a palladium complex. This reductive coupling could be chemoselectively applied to the preparation of trans-alkenes with various functional groups, such as an alkyl group, a halogen, an ester, a nitro group, a heterocycle, a boronic ester, and an internal alkyne.
- Takahashi, Keita,Ogiwara, Yohei,Sakai, Norio
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supporting information
p. 809 - 814
(2018/03/13)
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- Reactions of a cationic geminal Zr+/P pair with small molecules
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The metallocene cation complex [Cp*2ZrCH3] +[B(C6F5)4]- inserts the phosphino-substituted alkyne Ph-Ci - 1/4C-PPh2 into the [Zr]-CH3 bond to form the internally phosphane-stabilized cation [Cp*2Zr-C(=CMePh)PPh2]+ (10). Complex 10 adds alkyl isocyanides as well as pivalonitrile at a lateral site at the bent metallocene wedge with retention of the Zr-P bond. Complex 10 acts as a reactive frustrated Lewis pair toward heterocumulenes, undergoing Zr+/P addition reactions to the carbonyl groups of an alkyl isocyanate and of carbon dioxide to form the respective five-membered metallaheterocyclic adducts 13 and 14. With mesityl azide complex 10 undergoes a Zr+/P FLP N,N-addition reaction at the terminal azide nitrogen atom to form the four-membered FLP cycloadduct 15. The Zr+/P FLP is a reactive hydrogen activator. In a stoichiometric reaction it generates a hydridozirconocene cation that subsequently serves as a hydrogenation catalyst for various olefinic or acetylenic substrates. The Zr+/P pair 10 undergoes selective 1,4-addition reactions to conjugated enones and to a conjugated ynone to give the corresponding seven-membered metallacyclic Zr+/P FLP addition products. Many compounds of this study were characterized by X-ray diffraction.
- Xu, Xin,Kehr, Gerald,Daniliuc, Constantin G.,Erker, Gerhard
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supporting information
p. 6465 - 6476
(2013/06/26)
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- First tandem asymmetric conjugate addition of alkenyl nucleophiles and silyl trapping of the intermediate enolates
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The tandem asymmetric conjugate addition of alkyl or aryl groups to enones and subsequent silyl trapping has already been achieved and yields valuable silyl enol ethers. Herein, the first method for the respective addition of alkenyl groups is reported, which is based on a rhodium(I)-catalyzed addition of readily available alkenylzirconocenes. As prerequisite for silyl trapping, the initially formed enolates have to be transmetalated from zirconium to lithium by treatment with methyllithium prior to addition of the silyl chloride. Starting from 5- to 7-membered cycloalkenones, the respective silyl enol ethers were obtained in excellent yields and ≥93% ee; an acyclic substrate furnished a moderate enantioselectivity. Besides trimethylsilyl chloride, the silylation was also performed with tert-butyldimethylsilyl chloride, and the synthetic scope was evaluated by employing five different alkenyl groups. Moreover, the mechanism of this sequence was elucidated by 1H NMR studies, and the efficiency of catalyst control was exemplified by synthesis of a cis-3,5-disubstituted cyclohexanone which, due to strong substrate control, cannot be obtained by copper-catalyzed conjugate addition.
- Westmeier, Johannes,Pfaff, Christopher,Siewert, Juergen,Von Zezschwitz, Paultheo
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supporting information
p. 2651 - 2658
(2013/10/21)
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- Reactions of (Diphenylphosphinomethyl)zirconocene chloride with B(C 6F5)3: Competition between P/B and P/Zr + frustrated lewis pair reactions
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The title complex Cp2ZrCl(CH2PPh2) reacts with B(C6F5)3 under specific conditions by phosphinomethyl transfer to give the phosphane-stabilized salt [Cp 2ZrCl+][Ph2PCH2B(C6F 5)3-]. X-ray crystal structure analysis showed the P-Zr coordination. This salt is trapped by phenyl isocyanate in an in situ three-component reaction to yield the respective P/Zr+ frustrated Lewis pair (FLP) addition product. In contrast, a mixture of Cp 2ZrCl(CH2PPh2)/B(C6F 5)3 and benzaldehyde under similar conditions gives the P/B FLP addition product. The Cp2ZrCl(CH2PPh 2)/B(C6F5)3 system may form a P/B adduct [Cp2ZrCl(CH2PPh2)·B(C 6F5)3] or a P/Zr+ adduct [Cp 2ZrCl·PPh2CH2B(C6F 5)3]. From the former it seems to show P/B FLP reaction and from the latter P/Zr+ FLP behavior; the outcome is dependent on the specific reagent and reaction conditions chosen.
- Xu, Xin,Kehr, Gerald,Daniliuc, Constantin G.,Erker, Gerhard
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supporting information
p. 7306 - 7311
(2014/04/03)
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- Transition-metal-promoted or -catalyzed exocyclic alkyne insertion via zirconacyclopentene with carborane auxiliary: Formation of symmetric or unsymmetric benzocarboranes
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Reactions of Cp2Zr(μ-Cl)(μ-C2B 10H10)Li(OEt2)2 with alkynes R 1C≡CR2 gave as insertion products zirconacyclopentenes incorporating a carboranyl unit, 1,2-[Cp 2ZrC(R1)=C(R2)]-1,2-C2B 10H10 (1). Treatment of 1 with another type of alkyne R3C≡CR4 in the presence of stoichiometric amounts of NiCl2 and FeCl3 or a catalytic amount of NiCl2 afforded symmetric or unsymmetric benzocarboranes. The regioselectivity was dominated by the polarity of the corresponding alkynes. These reactions could also be carried out in one pot, leading to the equivalent of a three-component [2 + 2 + 2] cycloaddition of carboryne and two different alkynes promoted by transition metals. A reaction mechanism was proposed after the isolation and structural characterization of the key intermediate nickelacycle. These results show that nickel complexes are more reactive than the iron ones toward the insertion of alkynes but that the latter do not initiate the trimerization of alkynes, making the insertion of activated alkynes possible. This work also demonstrates that a catalytic amount of nickel works as well as a stoichiometric amount of nickel in the presence of excess FeCl3 for the reactions. Such a catalytic reaction may shed some light on the development of zirconocene-based catalytic reactions.
- Ren, Shikuo,Qiu, Zaozao,Xie, Zuowei
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p. 3242 - 3254
(2012/04/10)
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- Preparation of titanocene and zirconocene dichlorides bearing bulky 1,4-dimethyl-2,3-diphenylcyclopentadienyl ligand and their behavior in polymerization of ethylene
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New metallocene dichlorides [η5-(1,4-Me2-2,3-Ph2-C5H )2TiCl2] (2), [η5-(1,4-Me2-2,3-Ph2-C5H )2ZrCl2] (3) and [η5
- Horá?ek, Michal,Pinkas, Ji?í,Merna, Jan,Gyepes, Róbert,Meunier, Philippe
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p. 173 - 178
(2009/03/12)
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- Alkylaluminum-complexed zirconocene hydrides: Identification of hydride-bridged species by NMR spectroscopy
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Reactions of unbridged zirconocene dichlorides, (RnC 5H5-n)2ZrCl2 (n=0, 1, or 2), with diisobutylaluminum hydride (HAI'Bu2) result in the formation of tetranuclear trihydride clusters of the type (RnC5H 5-n)2Zr(μ-H)3(Al iBu2)3(μ-CI) 2, which contain three [Al iBu2] units. Ring-bridged ansa-zirconocene dichlorides, Me2E(RnC5H 4-n)2ZrCl2 with E=C or Si, on the other hand, are found to form binuclear dihydride complexes of the type Me2E(R nC5H4-n)2Zr(CI)(μ-H) 2Al iBu2 with only one [AIBu2] unit. The dichotomy between unbridged and bridged zirconocene derivatives with regard to tetranuclear versus binuclear product formation is proposed to be connected to different degrees of rotational freedom of their C5-ring ligands. Alkylaluminum-complexed zirconocene dihydrides, previously observed in zirconocene-based precatalyst systems activated by methylalumoxane (MAO) upon addition of HAI'Bu2 or Al iBu3, are proposed to be species of the type Me2Si(ind)2Zr(Me)(μ-H) 2Al iBu2, stabilized by interaction of their terminal Me group with a Lewis acidic site of MAO.
- Baldwin, Steven M.,Bereaw, John E.,Brintzinger, Hans H.
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p. 17423 - 17433
(2009/06/08)
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- Promotion of phosphaalkyne cyclooligomerisation by a Sb(V) to Sb(III) redox process
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A high yield of the tetraphosphaladderene, anti-tetraphosphatricyclo[4.2.0. 02,5]octa-3,7-diene, is obtained from reaction of the zirconocene 1,3-diphosphabicyclo[1.1.0]butane with Ph2SbCl3 in THF or CH2Cl2. Exploration of the reaction pathway using density functional theory suggests that an envelope-type adduct of Ph2SbCl and 1,3-diphosphabicyclo[1.1.0]butane plays a pivotal role in the reaction. The zwitterionic character of this intermediate species allows it to act simultaneously as both an ene and an eneophile, and a symmetry-allowed bimolecular reaction leads to the tetraphosphaladderene species via a spirocyclic intermediate.
- Fish, Cheryl,Green, Michael,Kilby, Richard J.,McGrady, John E.,Pantazis, Dimitrios A.,Russell, Christopher A.
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p. 3753 - 3758
(2009/02/02)
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- Synthesis, structure, and reactivity of four-, five-, and six-coordinate ruthenium carbyne complexes
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Square-planar carbyne complexes of the form Ru(≡CR)(PCy 3)2X (X = F, Cl, Br, I, O3SCF3) are prepared by net dehydrohalogenation of the Grubbs catalysts Ru(≡CHR) (PCy3)2Cl2 followed by substitution of the chloride ligand (when X ≠ Cl). The dehydrohalogenation can be effected in one step (R = n-Bu, Ph, p-C6H4Me) by Ge(CH[SiMe 3]2)2 or in two steps via treatment with excess aryloxide such as NaO-p-C6H4-t-Bu followed by SnCl 2. The latter route gives greater yields but is more restricted in scope. Addition of HCl (1 equiv) to Ru(=CR)(PCy3)2X (X = Cl, Br, I) affords Ru(=CHR)(PCy3)2ClX; those with mixed halide ligand sets undergo rapid halide exchange in solution. Upon treatment with the appropriate oxidant, each Ru(=C-p-C6H4Me) (PCy3)2X complex undergoes two-electron oxidation. Oxidation of Ru(=C-p-C6H4Me)(PCy3)2X (X = F, Cl, Br, I) by XeF2, C2Cl6, Br 2, and, respectively, yields either six-coordinate bis-phosphine complexes Ru(=C-p-C6H4Me)(PCy3) 2X3 (X = F, Cl) or square-pyramidal mono-phosphine complexes Ru(≡C-p-C6H4Me)(PCy3)X 3 (X = Br, I) depending on the size of the halide ligands. Cationic square-pyramidal complexes of the form [Ru(=C-p-C6H 4Me)(PCy3)2X2]+ (X = Cl, I) can be prepared from Ru(≡C-p-C6H4Me)(PCy 3)2Cl3 by chloride abstraction using [Ph 3C]BF4 and from Ru(≡C-p-C6H 4-Me)(PCy3)X3 by addition of PCy3. Hydride addition to Ru(≡C-p-C6H4Me)(PCy 3)2Cl3 yields the carbene complex Ru(=CHR)(PCy3)2Cl2, whereas fluoride addition affords the carbyne complex Ru(≡C-p-C6H4-Me(PCy 3)2Cl2F, results with important implications for metathesis of vinyl fluorides. X-ray structures of Ru(≡C-p-C 6H4Me)(PCy3)2X2F (X = F, Cl), [Ru(≡C-p-C6H4Me)PCy3) 2Cl2]BF4, and Ru(≡C-p-C6H 4-Me)(PCy3)I3 reveal short Ru≡C bonds in the 1.670(5)-1.714(3) A range; when two PCy3 ligands are present, they are mutually trans. The benzylidyne ligands occupy the apical sites in the two square-pyramidal complexes. Of the five- and six-coordinate complexes, only the two fluoride-containing complexes Ru(≡C-p-C 6H4Me)(PCy3)2X2F (X = F, Cl) display reactivity toward alkynes, serving as alkyne dimerization catalysts.
- Caskey, Stephen R.,Stewart, Michael H.,Yi, Joon Ahn,Johnson, Marc J. A.,Rowsell, Jesse L. C.,Kampf, Jeff W.
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p. 1912 - 1923
(2008/10/09)
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- Catalytic system for homogeneous ethylene polymerization based on aluminohydride-zirconocene complexes
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Ethylene polymerization using catalysts derived from activation of zirconocene aluminohydride complexes with either methyl aluminoxane or B(C 6F5)3 is reported. Variable-temperature NMR spectra of mixtures of Cp*2ZrH3AlH2 or Cp′2ZrH3AlH2 and excess B(C 6F5)3 reveal the formation of di- or polynuclear metallocenium ion-pairs featuring terminal or both terminal and bridging borohydride counteranions HB(C6F5)3 arising from hydride abstraction. At higher T, ion-pairs featuring the terminal HB(C6F5)3 counterion decompose, and the AlH3 that is liberated degrades B(C6F5) 3 to furnish mixtures of (C6F5) nAlH3-n and, in the case of Cp*2ZrH 3AlH2, a new ion-pair partnered with the diborohydride counteranion [Cp*2ZrH][(μ-H)2B(C 6F5)2]. The latter compound was independently prepared from Cp*2-ZrH2 and HB(C6F 5)2 and is active in ethylene polymerization; however it is 1000 times less active than the catalyst formed from Cp* 2ZrH3AlH2 and B(C6F 5)3 and so cannot account for the multisite behavior of the latter combination. There is evidence of chemical exchange between free or terminal HB(C6F5)3 and excess B(C6F5)3 in these mixtures, and on the basis of model studies with [nBu4N][HB(C6F 5)3] and B(C6F5)3, this involves reversible formation of [nBu4N][(C 6F5)3B)(μ-H)B(C6F 5)3], which can be detected by 19F NMR spectroscopy in solution at low T.
- Gonzalez-Hernandez, Rebeca,Jianfang, Chai,Charles, Rogelio,Perez-Camacho, Odilia,Kniajanski, Sergei,Collins, Scott
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p. 5366 - 5373
(2008/10/09)
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- Mechanism of Cp2ZrCl2-catalyzed olefin hydroalumination by alkylalanes
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The composition of intermediates of the Cp2ZrCl 2-catalyzed hydroalumination of α-olefins by isobutylalanes (HAlBui 2, AlBui 3, ClAlBu i 2) was studied by dynamic sup
- Parfenova,Pechatkina,Khalilov,Dzhemilev
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p. 316 - 327
(2007/10/03)
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- Sigma-bond metathesis reactions of zirconocene alkyl cations with phenylsilane
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The zirconocene methyl cations [(C5R5)ZrMe(ClC 6D5)] [B(C6F5)4] (C 5R5 = C5H5 (1a), C5H 4Me (1b)) react with PhSiH3 in the dark to yield [{(C 5R5)2Zr(μ-H)}2][B(C 6F5)4]2 (5a, b) and a mixture of PhxMeyHzSi products. The reaction proceeds by initial Zr-C/Si-H σ-bond metathesis via a four-center transition state in which Si is β to Zr. In the presence of light, significant amounts of [{(C5R5)2Zr(μ-Cl)}2] [B(C 6F5)4]2 (4a,b) are formed by photochemical reaction of (C5R5)2ZrH + species with the chlorobenzene solvent. The azazirconacycle [rac-(EBI)Zr{η2(C,N)-CH2CHMe(6-phenyl-2-pyridyl)}] [B(C6F5)4] (2, EBI = 1,2-ethylene-bis-indenyl) does not react with PhSiH3 at 23°C. However at 85°C, 2 deinserts propene to afford the η2-pyridyl complex [rac-(EBI)Zr{η2(C,N)-(6-phenyl-2-pyridyl)}][B(C6F 5)4] (6), which is catalytically isomerized to [rac-(EBI)Zr{η2(C,N)-2-(2-pyridyl)phenyl}][B(C6F 5)4] (7) by PhSiH3. The key step in this process is Zr-G/Si-H σ-bond metathesis of 6 with PhSiH3 via a transition state in which Si is α to Zr. The less crowded azazirconacycle [Cp2Zr{η2(C,N)-CH2CHMe-(6-methyl-2-pyridyl) }][B(C6F5)4] (3) reacts with PhSiH3 directly to afford [{Cp2Zr(SiPhH2)}2]-[B(C 6F5)4]2 (8) via a transition state in which Si is α to Zr. Steric factors may play a role in determining the selectivity of these reactions.
- Wu, Fan,Jordan, Richard F.
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p. 2688 - 2697
(2008/10/09)
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- Syntheses, structures, and properties of phenyltrihydroborate complexes of zirconocene and titanocene
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The phenyltrihydroborate complexes, Cp2ZrCl{(μ-H) 2BHPh}, 1, and Cp2Zr{(μ-H)2BHPh}2 ? (1/2 toluene), 2, were prepared from the reactions of Cp 2ZrCl2 with one and two moles of LiBH3Ph. The Zr-H-B bonds in 2 are stable under vacuum at 100°C for hours without significant decomposition. An inductive effect has been proposed for this strong interaction. This hydrogen bridge bond can be broken upon reacting with the Lewis base N(C2H5)3 to produce (C 2H5)3N ? BH2Ph and the zirconium hydride compound Cp2ZrH{(μ-H)2BHPh}, 3. Compound 3 also can be prepared from the reaction of Cp2ZrHCl with LiBH3Ph. The reaction of 1 with the Lewis acid B(C6F 5)3 is solvent dependent, the metathesis product Cp 2ZrCl{(μ-H)2B(C6F5)2}, 4, was formed in the toluene solution, whereas the ionic complex [Cp 2ZrCl(OEt2)][HB(C6F5)3], 5, was isolated from the ether solution. The reaction of titanocene dichloride, Cp2TiCl2, with LiBH3Ph produced a 17-electron, paramagnetic complex, Cp2Ti{(μ-H)2BHPh}, 6. Single crystal X-ray structures of 1, 2, 3, 4, 5, and 6 were also determined. A coplanar structure of the four bridge hydrogens in 2 was observed.
- Liu, Fu-Chen,Chen, Jung-Hua,Chen, Shou-Chon,Chen, Ko-Yu,Lee, Gene-Hsian,Peng, Shie-Ming
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p. 291 - 300
(2007/10/03)
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- Selective halodemethylation reactions of metallocene dimethyls with triphenylmethyl chloride and benzyl bromide
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NMR-scale reactions of several group 4 metallocene dimethyls with either trityl chloride or benzyl bromide gave the corresponding L2M(Me)X complexes selectively. Five reactions, including syntheses of Cp2-Zr(Me)Cl and Ind2Zr(Me)Cl, were conducted on a preparative scale to afford useful isolated yields of L2M-(Me)Cl complexes.
- Hawrelak, Eric J.,Deck, Paul A.
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- Preparation and properties of Cp2Zr(μ-N=CAr2) 2PdCl(Me), new Zr/Pd heterobimetallic complexes with bridging alkylideneamido ligands
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Zr/Pd heterobimetallic complexes with bridging alkylideneamido ligands, Cp2Zr(μ-N=CAr2)2PdCl(Me) (Ar = Ph, C 6H4Me-4), were prepared from the reaction of Cp 2Zr(N=CAr2)2 with PdCl(Me)(cod) (cod = 1,5-cyclooctadiene). Cp2Zr(μ-N=CAr2) 2PdCl(Me) complexes have puckered ZrN2Pd rings with Zr-Pd distances of 2.8135(5) A (Ar = Ph) and 2.8416(4) A (Ar = C 6H4Me-4), respectively. The complexes reacted with HCl to afford trans-PdCl(Me)(NH=CAr2)2 and Cp 2ZrCl2. Exposure of a CH2Cl2 solution of trans-PdCl(Me){NH= C(C6H4Me-4) 2}2 to light results in the formation of a mixture of cis- and trans-PdCl(CHCl2){NH=C(C6H4Me-4) 2}2.
- Kuwabara, Junpei,Takeuchi, Daisuke,Osakada, Kohtaro
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p. 5092 - 5095
(2008/10/09)
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- Convenient, zirconocene-coupling routes to germole- and thiophene-containing macrocycles with triangular geometries
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Reactions of zirconacyclopentadiene-coupled macrocycles with S2Cl2 or GeCl4 gave new macrocycles containing thiophene and dichlorogermole groups, respectively. The germoles, synthesized in high yields, possess labile chloride substituents that are readily displaced via nucleophilic substitution reactions. These germole-containing macrocycles are potentially useful as supramolecular building blocks. A macrocyclic trithiophene compound, with 1,4-phenylene groups that bridge the thiophene rings, was characterized by X-ray crystallography. The X-ray structure of a related trigermole macrocycle, with bridging biphenylene groups, is also presented.
- Nitschke, Jonathan R.,Don Tilley
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- Cyclic organohydroborate complexes of metallocenes. VII. Synthesis, structure, and fluxional behavior of Cp2ZrX{(μ-H)2BC8H14} (X = H, D, Cl)
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The reaction of K[H2BC8H14] with Cp2ZrCl2 in a 1:1 molar ratio afforded Cp2ZrCl{(μ-H)2BC8H14}, 1, which when reacted with KH yielded Cp2ZrH{(μ-H)2BC8H14}, 2. These complexes were structurally characterized by single-crystal X-ray analysis. Partially deuterated 1 and 2, complexes Cp2ZrCl{(μ-D)(μ-H)BC8H14}, 3, and Cp2ZrD{(μ-H)2BC8H14}, 4, were prepared. 2H NMR spectra revealed that in complex 3, which contains a terminal chloride on zirconium, no exchange of bridge and Cp hydrogens occurred. However, in complex 4, which includes a terminal hydrogen on zirconium, there was facile mixing of terminal, bridge, and Cp-hydrogens. Furthermore, exchange of terminal zirconium-hydrogen with bridge hydrogen was more rapid than exchange with the Cp-hydrogen. Additionally, this fluxional behavior occurred even at room temperature and in the solid state. Variable-temperature 1H NMR studies are consistent with these results of dynamic hydrogen exchange in complexes 1 and 2. The complexes Cp2Nb{(μ-H)2BC8H14}, 7, and Cp2Nb{μ-D)(μ-H)-BC8H14}, 8, have no terminal hydrogen on niobium, and there is no exchange between bridging hydrogens and Cp-hydrogens. The possible participation of the 9-BBN unit ({(μ-H)2BC8H14}) hydrogens in dynamic exchange was examined for 2, the 9-BBN dimer ((C8H14B)(μ-H)2(BC8H14 )), and the 9-BBN anion ([H2BC8H14]) through the partially deuterated complexes Li[(D)(H)BC8H14], 5, and (C8H14B)(μ-D)(μ-H)(BC8H14), 6.
- Chen, Xuenian,Liu, Shengming,Plecnik, Christine E.,Liu, Fu-Chen,Fraenkel, Gideon,Shore, Sheldon G.
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p. 275 - 283
(2008/10/08)
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- Methyl-versus-chloride exchange as a measure of electron density at the metal center of ring-substituted zirconocene complexes
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Methyl-versus-cloride exchange equilibria between different zirconocene complexes provide a sensitive measure of relative electron densities at the Zr centers of these complexes. As expected, methyl and trimethyl silyl substituents increase the electron density at the Zr center of a bis(cyclopentadienyl) Zr(IV) complex; the same holds for a dimethyl silyl bridge. In bis(indenyl) complexes, on the other hand, electron density at the metal center is reduced and substituent and bridge effects are different from those observed in bis(cyclopentadienyl) Zr(IV) complexes.
- Weiser, Ulrich,Babushkin, Dimitrii,Brintzinger, Hans-Herbert
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p. 920 - 923
(2008/10/08)
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- Reactions of zirconacyclopentadienes with nitrosobenzene. Characterization of zirconacycle intermediates and formation of N-phenylpyrroles
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Nitrosobenzene inserts into the Zr-C bond of zirconacyclopentadienes to give seven-membered zirconacyclic rings. The resulting insertion products are readily converted to N-phenylpyrroles and (in one case) a 3,3-spiroindole derivative.
- Nakamoto, Masaaki,Tilley, T. Don
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p. 5515 - 5517
(2008/10/08)
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- A new chiral metalladiphosphine for early-late chemistry. Crystal structure of a D-camphor-based zirconium enolato phosphine and rearrangement of heterobimetallic Zr/Pd complexes
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The bis(phosphinoenolato) zirconocene 2, prepared from the phosphino camphor derivative 3-exo-PPh2C10H15O 1, represents the first C2-symmetric chiral diphosphine containing an early transition metal centre tethered to the phosphino groups via an enolato linkage. It allows the selective assembly of Lewis-acid early-late bimetallic combinations, as exemplified with the Zr/Cu and Zr/Ag complexes 4 and 5. The monophosphinoenolato titanocene 3 was also prepared. Reactions of 2 or 3 with [Pd(dmba)(μ-Cl)]2 (dmba = o-C6H4CH 2NMe2) or [PdCl2(SEt2)2] led to complete transfer of the functional ligand to the Pd(II) centre, with formation of [(dmba)Pd(PPh2C10H14O)] 6 or cis-[Pd(PPh2C10H14O)2] 8 and [Cp2ZrCl2]/[Cp2TiCl2], respectively. A heterobimetallic Zr/Pd intermediate complex 10 of this rearrangement could be detected. Complexes 6 and 8 were prepared independently by reaction of 1 with [Pd(dmba)(μ-Cl)]2 or [Pd(SEt2)2Cl 2], respectively, which first afforded complexes 7 and 9 which were then treated with KH. The crystal structures of 2, 6 and 8·THF· H2O have been determined by X-ray diffraction. The Royal Society of Chemistry 2001.
- Mattheis, Chris,Braunstein, Pierre,Fischer, Axel
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p. 800 - 805
(2007/10/03)
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- Synthesis and structure of semi(tetrahydrofuran-O)bispotassium bis(2,3,4,5-tetraethylstibolide)
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The reaction of bis(cyclopentadienyl)zircona-2,3,4,5- tetraethylcyclopentadiene (1) with antimony trichloride yields 1-chloro-2,3,4,5-tetraethyl-1-stibole (2). The reduction with potassium gives semi(tetrahydrofuran-O)bispotassium bis(2,3,4,5- tetraethylstibolide) (3). The potassium stibolide columns are linked via K-Sb contacts of 3.618 angstrom, thus forming a wavelike layer structure. The molecular structure shows three crystallographically different metal cations. One potassium atom is located between two stibolide anions, whereas the other ones show additional K-O and K-Sb contacts of 2.681 and 3.618 angstrom, respectively.
- Westerhausen, Matthias,Gückel, Christian,Warchhold, Marcus,N?th, Heinrich
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p. 2393 - 2396
(2008/10/08)
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- Synthesis and conversions of metallocycles 22. NMR studies of the mechanism of Cp2ZrCl2-catalyzed cycloalumination of olefins with triethylaluminum to form aluminacyclopentanes
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The mechanism of cycloalumination of olefins under the action of AlEt3 in the presence of Cp2ZrCl2 giving rise to aluminacyclopentanes was investigated by dynamic 1H and 13C NMR spectroscopy. The bimetallic complex Cp2ZrEtCl-AlEt3 is formed initially and is converted into the bridged complex Cp2Zr(Cl)CH2CH2AlEt2 as a result of β-hydride shift and elimination of the ethane molecule. The resulting complex adds a molecule of the initial olefin yielding aluminacyclopentanes. Under the action of Et2AlCl in the presence of an excess of AlEt3, zirconacyclopentanes give rise to intermediate bimetallic complexes stable at -70 °C. Under the reaction conditions, the latter compounds are converted into aluminacyclopentanes.
- Khalilov,Parfenova,Rusakov,Ibragimov,Dzhemilev
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p. 2051 - 2058
(2007/10/03)
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- Carbon-fluorine bond cleavage by zirconium metal hydride complexes
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The zirconium hydride dimer [Cp2ZH2]2 reacts with C6F6 at ambient temperature to give Cp2Zr(C6F5)F as the major product along with Cp2ZrF2, Csub
- Edelbach, Brian L.,Rahman, A.K. Fazlur,Lachicotte, Rene J.,Jones, William D.
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p. 3170 - 3177
(2008/10/08)
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- Insertion of 1-chloro-1-lithioalkenes into organozirconocenes. A versatile synthesis of stereodefined unsaturated systems
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Hydrozirconation of alkenes and alkynes, followed by insertion of 1- halo-1-lithio-1-alkenes, generated in situ by lithium tetramethylpiperidide deprotonation of vinyl halides, affords vinylzirconocene species which may be further elaborated. The method provides easy access to many structures including terminal (3E)- and (3Z)-1,3-dienes and (3E,5E)- and (3Z,5E)-1,3,5- trienes, and internal (E,Z)-dienes,(E,Z,E)-trienes, and (1E, 3Z)1,3-dien-5- ynes. Insertion of 2-monosubstituted 1-halo-1-lithio-1-alkenes occurs with clean inversion of configuration of the sp2-carbenoid carbon. Carbenoids derived by deprotonation of 2,2-disubstituted 1-halo-1-alkenes gave poor stereocontrol probably due to isomerization before insertion into the organozirconium species. Insertion of vinyl carbenoids into alkynylzirconocenes affords terminal (3E)- or (3Z)-1,3-dien-5-ynes, internal (1E,3Z)-1,3-dien-5-ynes, and (Z)-3-en-1,5-diynes.
- Kasatkin, Aleksandr,Whitby, Richard J.
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p. 7039 - 7049
(2007/10/03)
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- New O- and N-bonded zirconocene complexes and their catalytic properties in ethylene polymerization. X-ray crystal structure of (C5H5)2Zr{2,6-OC6H 3(CH3)2}2, (C5H5)2Zr{2,4,6-OC6H 2(CH3)3}2
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A series of zirconocene complexes of formula Cp2ZrMe2-nLn where Cp = C5H-5, Me = methyl, L = pyrazolyl, bis(N,N′-phenylformamidinato), or substituted aryloxide and n = 1,2, were synthesized by reaction of Cp2ZrCl2 and Cp2ZrMe2 with LiL or HL, respectively. The structures of Cp2Zr(2,6-OC6H3Me2)2, Cp2Zr(2,4,6-OC6H2Me3)2 and Cp2ZrMe{CH(NC6H5)2} were determined by single crystal X-ray diffraction. The complexes demonstrate appreciable activity for ethylene polymerization when used as cocatalysts with methylaluminoxane and dimethylanilinium tetrafluorophenylborate.
- Benetollo,Cavinato,Crosara,Milani,Rossetto,Scelza,Zanella
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p. 177 - 185
(2007/10/03)
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- Mechanistic aspects of the reactions of bis(pentafluorophenyl)borane with the dialkyl zirconocenes Cp2ZrR2 (R = CH3, CH2SiMe3, and CH2C6H5)
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The reactions of bis(pentafluorophenyl)borane with simple dialkyl zirconocenes Cp2ZrR2 (R = CH3, CH2SiMe3, CH2Ph) proceed via initial alkyl/hydride exchange to yield Cp2Zr-(H)R and RB(C6F5)2. Two reaction paths are then followed depending on whether further equivalents of HB(C6F5)2 are present or not. If present, HB(C6F5)2 reacts with the newly formed Zr-H moiety to form dihydridoborate compounds, ultimately yielding Cp2Zr[(μ-H)2B-(C6F5) 2]2, 1, and 2 equiv of RB(C6F5)2. Compound 1 was characterized by X-ray crystallography. In the absence of more HB(C6F5)2, the products of alkyl/hydride exchange react to eliminate RH and produce the borane-stabilized alkylidene compounds Cp2Zr(μ-CH2)[(μ-H)B(C6F5) 2], 2, and Cp2Zr{η3-CH(C6H 5)[μ-H)B(C6F5)2]}, 4. The latter compound is formed cleanly in 92percent yield and was characterized by X-ray crystallography. Mechanistic studies on these reactions involving partially deuterated compounds reveal that the alkyl/hyride exchange process is reversible and takes place via a stepwise alkide-abstraction-hydridereplacement sequence rather than a concerted, four-centered σ-bond metathesis type mechanism. This is most convincingly demonstrated by the observed inversion of stereochemistry observed when erythro-Cp2Zr[CH(D)CH(D)-t-C4H9](Cl) (3JHH = 12.82 ± 0.05 Hz) is treated with excess HB(C6F5)2, producing threo-(C6F5)2B-CH(D)CH(D)-t-C4H 9 (3JHH = 5.00 ± 0.05 Hz). Further experiments reveal a H/D scrambling process involving the borane proton and the Cα-H positions of the zirconium alkyl groups (R = CH3, CH2Ph). For example, treatment of Cp2Zr(CD2C6D5)2 with 1 equiv of HB(C6F5)2 leads to a mixture of isotopomers of 4 and toluene, including C6D5CH3 and C6D5CH2D, suggesting a scrambling process in which the borane engages in multiple contacts with the metallocene reagent prior to alkane elimination. The HTD scrambling event is proposed to involve hydridoborate attack of the remaining alkyl group on the forming metallocene cation as HB(C6F5)2 abstracts the other alkide ligand. The implications of these mechanistic studies within the realms of metallocene activation and metallocene-catalyzed hydroborations are discussed.
- Spence, Rupert E.V.H.,Piers, Warren E.,Sun, Yimin,Parvez, Masood,MacGillivray, Leonard R.,Zaworotko, Michael J.
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p. 2459 - 2469
(2008/10/08)
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- Diastereoselective synthesis of highly substituted five-membered-ring oxygen heterocycles by zirconocene-mediated C - C coupling reactions
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As homoenolate equivalents, zirconocene-1-aza-1,3-diene complexes were used for the first time in stereoselective synthesis. By insertion of an unsymmetrical ketone in the Zr-C σ bond, sterically demanding trisubstituted dihydro- and tetrahydrofuran derivatives were prepared in good overall yields and with high diastereoselectivities (see below).
- Enders, Dieter,Kroll, Manfred,Raabe, Gerhard,Runsink, Jan
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p. 1673 - 1675
(2007/10/03)
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- Synthesis and structural studies on mono- And bis(cyclopentadienyl)titanium(IV)/zirconium(IV) derivatives of ferrocenyl hydrazones
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The reactions of hydrazones, derived by the condensation of acetylferrocene with different aromatic acid hydrazides (benzoic, 2-chlorobenzoic, nitrobenzoic, methylbenzoic), with mono(cyclopentadienyl)titanium(IV) trichloride and bis(cyclopentadienyl) titanium (IV)/zirconium (IV) dichloride have been studied in anhydrous tetrahydrofuran or dichloromethane in the presence and absence of amine. Tentative structural conclusions are drawn for the reaction products based upon elemental analysis, electrical conductance, magnetic moment and spectral (electronic, infrared and 1H NMR) data.
- Srivastava,Srivastava,Gupta,Pandey,Sengupta
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p. 778 - 782
(2007/10/03)
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- Synthesis and reactivity of titanocene and zirconocene triflates
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The synthesis of inflate derivatives of titanocene and zirconocene from the corresponding dimethyl complexes and triflic acid (HOTf) is described. Comproportionation of Cp2M(OTf)2 with Cp2MX2 gives Cp2/sub
- Luinstra, Gerrit A.
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p. 209 - 215
(2007/10/03)
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- Phosphinidene transfer reactions of the terminal phosphinidene complex Cp2Zr(PC6H2-2,4,6-t-Bu3)(PMe 3)
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The terminal zirconium phosphinidene complex Cp2Zr(PR*)(PMe3) (R* = C6H2-2,4,6-t-Bu3) 2 has been synthesized in high yield, and its reactivity has been investigated. The compound Cp2ZrMe(PH
- Breen, Tricia L.,Stephan, Douglas W.
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p. 11914 - 11921
(2007/10/03)
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- Seven-Membered Heterodimetallic Ring Systems from (Conjugated Diene) Group 4 Metallocene Complexes and Organoaluminium Reagents
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The (s-trans/s-cis-η4-butadiene)zirconocene reagent adds dimethylaluminium chloride to yield the heterodimetallacyclic main group/transition-metal system 2b, containing a seven-membered metallacyclic framework that exhibits a ?-agostic ?-allyl zirconium interaction.Similar compounds (2c-f, 5a, 6) are obtained upon reaction of (butadiene)zirconocene with Et2AlI and (butadiene)hafnocene with Me2AlCl or Et2AlI.Addition of Me2AlCl or Et2AlI to (isoprene)zirconocene proceeds regioselectively to yield the corresponding heterodimetallacycles bearing the methyl substituent at C-3 (i.e. near to the attached aluminium center).The iodide-bridged heterodimetallacycles exhibit dynamic NMR spectra that indicate a rapid enantiomerization process on the NMR time scale (ΔG(act.)ent ca. 11 - 12 kcal mol-1).It is assumed that this automerization reaction proceeds by rate-limiting aluminium-halogen bond cleavage leading to an acyclic mixed metal heterodimetallic intermediate.This process is markedly inhibited by the presence of excess diethylaluminium iodide. - Key Words: Bent metallocene complexes / Heterodimetallic zirconium-aluminium compounds / Hydrocarbyl-bridging ligands / ?-Agostic interaction
- Erker, Gerhard,Noe, Ralf,Wingbermuehle, Doris
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p. 805 - 812
(2007/10/02)
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