- IR studies at elevated gas pressures. III. Kinetics of the CO induced disproportionation of (C5(CH3)5)2TiX (X=Cl, Br, I)
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The disproportionation of Cp*2TiClCO (Cp*=μ5-C5(CH3)5) (formed from Cp*2TiCl and CO in toluene solution) into Cp*2TiCl2 and Cp*2Ti(CO)2 has been studied at CO pressures of between 2 and 90
- Luinstra, Gerrit A.,Teuben, Jan H.,Brintzinger, Hans-Herbert
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- Preparation, structure, and reactivity of a (pentamethylcyclopentadienyl)titanium dimer bridged by oxygen and tetramethylmethylenecyclopentadienyl
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The reaction between Cp*2Ti (Cp* = η5-C5(CH3)5) and N2O in toluene affords [(Cp*Ti)2-μ-(η1:η5-C 5(CH3)4CH2)(μ-O)2] (I). The structure of the product was determined by X-ray diffraction; it crystallizes in the orthorhombic space group Pnma with a = 10.650 (5) A?, b = 15.283 (3) A?, c = 17.064 (8) A?, and Z = 4. The structure was refined to R = 0.048 and Rw = 0.052 for 256 parameters and 1226 observed reflections. The molecule consists of two (η5-C5(CH3)5)Ti units bridged unsymmetrically by two oxygen atoms (Ti(1)-O = 1.961 (3) A? and Ti(2)-O = 1.787 (3) A?) and an η1:η5-C5(CH3) 4CH2 ligand (η1 to Ti(2) and η5 to Ti(1)). The bond distances are in agreement with the description of the C5(CH3)4CH2 bridge as a truly methylenic η1:η5 ligand and not as an η2:η4 olefinic ligand. The Ti(2)-CH2 distance is 2.178 (6) A?; all other C-C and Ti-C distances are normal for Cp*Ti units. The methylenic description of C5(CH3)4CH2 is supported by NMR (δ(CH2) 50.4 in the 13C spectrum) and IR (ν(C-H) 2960, 2900, and 2850 cm-1) spectroscopies and also explains the remarkable stability of I (no reaction with H2, CO, or C2H4) since both titanium atoms are Ti(IV). With HCl, I gives Cp*2TiCl2 and Cp*TiCl3.
- Bottomley, Frank,Egharevba, Gabriel O.,Lin, Ivan J. B.,White, Peter S.
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- Titanocene - 1,4,6-tris(trimethylsilyl)hex-3-ene-1,5-diyne-3-yl complexes - Crystal structures and their retro reaction
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The formation of the π-coordinated 1,4,6-tris(trimethylsilyl)hex-3-ene- 1,5-diyne-3-yl ligand at the (TiIII) atom is a general reaction for highly methyl-substituted titanocenes. The retroreaction to 1,4- bis(trimethylsilyl)buta-1,3-diyne is induced by oxidation with PbCl2. Paramagnetic titanocene complexes containing the unsaturated carbyl group which consists of one and half molecule of 1,4-bis(trimethylsilyl)buta-1,3-diyne (BSD) are formed by the reduction of titanocene dichlorides with one molar equivalent of magnesium in the presence of 1.5 molar equivalent BSD in tetrahydrofuran (THF) for titanocene moieties Ti(η5-C 5H5 - nMen)2 (n = 5 (1), 4 (2), and 3 (3)) and Ti{Me2Si(η5-C5Me 4)2} (4). The non-methylated titanocene moiety affords under identical conditions known diamagnetic bis(η5- cyclopentadienyl)-2,4-bis(trimethylsilylethynyl)-3,5-bis(trimethylsilyl) titanacyclopenta-2,4-diene (5) as the major product. Crystal structures of 3 and 4 show the same bonding scheme for the 1,4,6-tris(trimethylsilyl)hex-3-ene-1,5- diyne-3-yl ligand as previously found for compound 1 [P.-M. Pellny, F.G. Kirchbauer, V.V. Burlakov, A. Spannenberg, K. Mach, U. Rosenthal, Chem. Commun. (1999) 2505]. Compound 1 is stable against weak proton donors like methanol or alk-1-ynes even at 90°C, however, it undergoes retroreaction when oxidized by PbCl2 in THF, yielding nearly quantitatively BSD and [TiCl 2(η5-C5Me5)2].
- Horá?ek, Michal,Císa?ová, Ivana,Kubi?ta, Ji?í,Spannenberg, Anke,Dallmann, Kai,Rosenthal, Uwe,Mach, Karel
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- Effects of methyl substituents at the cyclopentadienyl ligand on the properties of C2H5TiCl3 and C5H5TiAl2CL8-x(C2H5)x (x = 0-4) complexes
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The methyl substituents in the series of pTiCl3 compounds (p = Cp, MeCp, Me3Cp, Me4Cp, Me5Cp and EtMe4Cp) shift the position of their CT absorption band from λ = 384 nm to max. 438 nm and decrease the rate of reduction of pTiCl3 by ethylaluminium
- Mach, Karel,Varga, Vojtech,Antropiusova, Helena,Polacek, Jindrich
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- Mono- and dilithiation of [(η7-C7H 7)Ti(η5-C5Me5)] (Pentamethyltroticene) for the synthesis of troticenyl monophosphanes and [2]troticenophanes with C-P and C-Si Bridges
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Pentamethyltroticene, [(η7-C7H 7)Ti(η5-C5Me5)] (1), can be selectively metalated at the C7H7 ring or at both the C5Me5 and C7H7 rings using pmdta/nBuLi or pmdta/tBuLi mixtures (pmdta = N,N′,N′,N″, N″-pentamethyldiethylenetriamine) in 1/1 and 1/4 ratios, respectively. The mono- and dilithiated species [(η7-C7H 6Li)Ti(η5-C5Me5)]·pmdta (2) and [(η7-C7H6Li)Ti(η5- C5Me4CH2Li)]·pmdta (3) were isolated in high yield and characterized by NMR spectroscopy and elemental analysis. Compound 2 was used to synthesize the pentamethyltroticenyl monophosphane [(η7-C7H6PPh2) Ti(η5-C5Me5)] (4) by reaction with Ph 2PCl, while 3 was treated with RPCl2 (R = Ph, Mes) or Me2SiCl2 to give the carbaphospha- and carbasila[2]troticenophanes [(η7-C7H 6)Ti(η5-C5Me4CH2)]PR (5, R = Ph; 6, R = Mes) and [(η7-C7H 6)Ti(η5-C5Me4CH 2)]SiMe2 (8). The chiral phosphanes 5 and 6 are the first examples of non-iron metallocenophanes with a phosphorus atom in the bridge. The coordination ability of 4 and 6 toward transition metals was demonstrated by reaction with Mo(CO)6 and [(tht)AuCl] (tht = tetrahydrothiophene) or Me2SAuCl and formation of the bimetallic complexes [{η7-C7H6PPh2·Mo(CO) 5}Ti(η5-C5Me5)] (9), [(η7-C7H6PPh2·AuCl) Ti(η5-C5Me5)] (10), and [(η7-C7H6)Ti(η5-C 5Me4CH2)]PMes·AuCl (11). These compounds were structurally characterized by multinuclear 1H, 13C, 31P, and 29Si NMR spectroscopy, UV/vis spectroscopy, electron ionization mass spectrometry (EI-MS), elemental analysis, and single-crystal X-ray diffraction analysis. The molecular structures of 5, 6 and 8 reveal strained sandwich compounds with tilt angles (α) of 18.5(1)° (5), 19.7(7)° (6), and 13.4(2)° (8). Treatment of 2 with ZnCl 2 afforded the pentamethyltroticenyl zinc chloride [(η7-C7H6ZnCl)Ti(η5-C 5Me5)] (12), which was employed in palladium-catalyzed Negishi C-C cross-coupling reactions with phenyl iodide and iodotroticene to afford phenylpentamethyltroticene [(η7-C7H 6Ph)Ti(η5-C5Me5)] (13) and the [7-5]bitroticene [(η7-C7H6)Ti{μ- η5:η7-(C5H4-C 7H6)}Ti(η5-C5Me5)] (14), which bears a bridging sesquifulvalene ligand. The molecular structures of 13 and 14 in the solid state were also determined by single-crystal X-ray diffraction analysis.
- Tagne Kuate, Alain C.,Mohapatra, Swagat K.,Daniliuc, Constantin G.,Jones, Peter G.,Tamm, Matthias
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- 5-C5Me5)2Ti>2(μ-OC)22 (cp = η5-C5H5): A Compound with Linear Coordination of Titanium to a Bridging Carbonyl and a d6-d6 2 Fragment
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Reaction of (η5-C5Me5)2Ti-neo-C5H11 with 2 (cp = η5-C5H5) yields the title compound (1); X-ray analysis of (1) shows a 4e (?, ?) Ti-O interaction, resulting in a novel linear co-ordination of titanium to a bridging carbonyl and a new geometry of a 2 fragment caused by a d6-d6 (Mo-Mo) electron count.
- Boer, Eric J. M. de,With, Jan de,Orpen, A. Guy
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- Interaction of carbon dioxide with the bis(trimethylsilyl) acetylene complex of permethyltitanocene: Synthesis and structure of the binuclear carbonate complex of permethyltitanocene (Cp2 Ti) 2CO3
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It has been shown that in the interaction of carbon dioxide with the bis(trimethylsilyl)acetylene complex of permethyltitanocene Cp2* Ti(Me3SiC2SiMe3), full displacement of bis(trimethylsilyl)acetylene from the
- Burlakov,Dolgushin,Yanovsky,Struchkov,Shur,Rosenthal,Thewalt
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- New titanocene complexes [Cp2Ti(μ-S2)2NR] (with R = Me and nOct) as transfer reagents for the synthesis of the heterocycles S5NR and S6NR
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The reaction of 1,4-S4(NR)2 with (η5-C5H5)2Ti(CO)2 yields [Cp2Ti(μ-S2)2NR] which on treatment with SCl2 or S2Cl2
- Schumann, Oliver,Steudel, Ralf
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- Reactivity Study of Pyridyl-Substituted 1-Metalla-2,5-diaza-cyclopenta-2,4-dienes of Group 4 Metallocenes
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In this work the reactivity of 1-metalla-2,5-diaza-cyclopenta-2,4-dienes of group 4 metallocenes, especially of the pyridyl-substituted examples, towards small molecules is investigated. The addition of H2, CO2, Ph?C≡N, 2-py?C≡N, 1,3-dicyanobenzene or 2,6-dicyanopyridine results in exchange reactions, which are accompanied by the elimination of a nitrile. For CO2, a coordination to the five-membered cycle occurs in case of Cp*2Zr(N=C(2-py)?C(2-py)=N). A 1,4-diaza-buta-1,3-diene complex is formed by H-transfer in the conversion of the analogous titanocene compound with CH3?C≡N, PhCH2?C≡N or acetone. For CH3?C≡N a coupling product of three acetonitrile molecules is established additionally. In order to split off the metallocene from the coupled nitriles, we examined reactions with HCl, PhPCl2, PhPSCl2and SOCl2. In the last case, the respective thiadiazole oxides and the metallocene dichlorides were obtained. A subsequent reaction produced thiadiazoles.
- Becker, Lisanne,Rei?, Fabian,Altenburger, Kai,Spannenberg, Anke,Arndt, Perdita,Jiao, Haijun,Rosenthal, Uwe
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supporting information
p. 10826 - 10838
(2016/07/27)
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- Synthesis, Cycloaddition, and Cycloreversion Reactions of Mononuclear Titanocene-oxo Complexes
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Titanocene-oxo complexes of the type Cpx2Ti=O(L) (Cpx = pentamethylcyclopentadienyl; tetramethylcyclopentadienyl; L = pyridine or derivatives) are synthesized from the corresponding titanocene-ethylene complexes via oxidation with pyridine N-oxides or styrene oxide. These oxo complexes react with alkynes, nitriles, and α,β-unsaturated carbonyls to form titanacycles, which undergo exchange reactions with organic substrates or react with 4-dimethylaminopyridine to regenerate the titanocene-oxo. Mechanistic experiments support a dissociative mechanism in which the first step is rate-determining retrocycloaddition followed by trapping of the reactive [Cpx2Ti=O] species. In the case of the retro-[4+2]-cycloaddition from dioxatitanacyclohexene complexes, a Hammett study gives ρ values of -1.18 and -1.04 for substituents on two different phenyl rings on the metallacycles, suggesting positive charge buildup and a slightly asynchronous cycloreversion in the rate-determining step.
- Nguyen, Trang T.,Kortman, Gregory D.,Hull, Kami L.
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p. 1713 - 1725
(2016/07/06)
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- Nitrile-nitrile C-C coupling at group 4 metallocenes to form 1-metalla-2,5-diaza-cyclopenta-2,4-dienes: Synthesis and reactivity
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The C-C coupling of aryl nitriles at Group 4 metallocenes leads to unusual ring-strained 1-metalla-2,5-diaza-cyclopenta-2,4-dienes. The structural, energetic, and chemical properties of these complexes are described. The reactions of these compounds towar
- Becker, Lisanne,Arndt, Perdita,Jiao, Haijun,Spannenberg, Anke,Rosenthal, Uwe
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supporting information
p. 11396 - 11400
(2013/11/06)
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- Reduction-induced double bond coordination and multiple C-H activation in fully-substituted titanocenes bearing a pendant double bond or an eight-membered hydrocarbyl ansa-chain
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Reduction of isomeric, fully-substituted titanocene dichlorides having a pendant double bond, the presence of bis(trimethylsilyl)ethyne (btmse) affords different products depending on the alkenyl chain length. Whereas the reduction of 1 yields a compound with intramolecularly η2-coordinated double bond, [Ti(η5-C5Me5) {η2:η5-C5Me4 (CH2CH2CH=CH2)}] (3), compound 2 affords under identical conditions a product with two new Ti-C bonds, [Ti{(η1:η1:η5- C5Me3(CH2)(CH(Me)CH2 CH2)}(η5-C5Me5)] (4). The formation of 3 can be rationalized as a simple intramolecular stabilization of a titanocene intermediate formed by reductive removal of the chloride ligands. The formation of 4 from the respective titanocene, however, requires formally an activation (oxidative addition) of one C-H bond at the methyl group adjacent to the unsaturated chain followed by a hydrogen shift (hydrometallation). Under similar conditions, the complex with asymmetric unsaturated ansa-bridge [TiCl2{η5:η5-C5 Me4CH2CH=CH(CH2)5C 5Me4}] (5) is reduced to a titanocene-η2-alkene complex with the double bond shifted to the central position, ansa-[Ti{η2:η 5:η5-C5Me4 (CH2)3CH=CH(CH2) 3C5Me4}] (7). In the absence of btmse, analogous complex with saturated bridge ansa-[TiCl2{η5:η5 -C5Me4(CH2)8C 5Me4}] (6) undergoes a hydrogen abstraction to give 7 as well albeit in a lower yield. The reduction of 6 in the presence of btmse gives η2-alkyne complex ansa-[Ti{η5:η5-C5Me4 (CH2)8C5Me4} (η2-Me3SiC≡CSiMe3)] (8) which is converted upon thermolysis at 150 °C to a mixture of asym- and sym-isomers of the doubly tucked-in complex ansa-[Ti{(η3:η4-C5Me2 (CH2)2)(CH2)8 (η5-C5Me4)}] (9) in 2:1 ratio; no C-H activation involving methylene groups of the ansa tether was observed. The crystal structures of 4, 7, and 8 have been determined by X-ray crystallography.
- Horá?ek, Michal,?těpni?ka, Petr,Kubi?ta, Ji?í,Císa?ová, Ivana,Petrusovaá, Lidmila,Mach, Karel
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p. 154 - 166
(2007/10/03)
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- Synthesis and structural characterization of azatitanacyclobutane derivatives
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The titanocene vinylidene intermediate [Cp*2Ti=C=CH2] (9) reacted with the carbodiimides R-N=C=N-R [R = p-CH3C6H11 (19a), C6H11 (19b)] to give the N=C-cycloaddition products [Cp *2Ti{-NR-C(=NR)-(C=CH2)-}] [(R = p-CH3C6H11 (20a), C6H11 (20b)]. The X-ray structure of 20a in form of a surprisingly stable n-hexane clathrate is presented. The azatitanacyclobutane [Cp *2Ti{-NPh-C(Ph)(H)-(C= CH2)-}] (22) was formed from the reaction between 9 and benzylidene aniline [PhN=C(Ph)H (21)]. Reactivity studies showed that azatitanacyclobutanes are unreactive upon typical ring-enlargement reactions as observed for other four-membered titanacycles.
- Beckhaus, Rüdiger,Wagner, Martin,Wang, Ruimin
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p. 253 - 256
(2007/10/03)
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- Early-transition-metal ketenimine complexes: Synthesis, reactivity, and structure of ketenimine-containing titanocene and zirconocene complexes
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Reaction of Cp2M(PMe3)2 complexes (M = Ti, Zr; Cp = η5-C5H5) with the N-(p-tolyl)-diphenylketenimine Ph′N=C=CPh2 (Ph′ = p-MeC6H4) in a 1:1 molar ratio affords the ketenimine-containing metallocene derivatives Cp2M(η2-(C,N)-Ph′N=C=CPh2)(PMe 3) (M = Ti (1); Zr (2)). The ketenimine ligand reacts in the same way with the Cp*2M species (Cp* = η5-C5Me5) generated from the reduction of the corresponding Cp*2MCl2 complexes with LitBu (1:2 molar ratio) to give the related complexes Cp*2M(η2-(C,N)-Ph′N=C=CPh2) (M = Ti (3); Zr (4)). The molecular structure of 3 shows a titanium atom bonded to two η5-cyclopentadienyl rings and a η2 -(C,N)-bonded ketenimine ligand. Reaction of Cp*2Ti with the ketenimine ligand in a 1:2 molar ratio gives 1,1,5,5-tetraphenyl-3-(p-tolyl)-2-(p-toluidino)-3-aza-1,4-pentadiene, which probably results from the coupling, followed by hydrolysis, of two ketenimine molecules coordinated to one titanocene moiety. Protonation of 3 with Et3NHCl or H2O (1:1 molar ratio) affords the intermediate species Cp*2Ti(X)(η2-(C,N)-Ph′N=C(H)-CPh 2) (X - Cl (5); OH (6)), which on hydrolysis evolves to give the enamine Ph′N(H)-CH=CPh2 as the final product. Finally, 3 reacts reversibly with H2 to give the hydride enamidate complex Cp*2Ti(H)(η1-Ph′N-CH-CPh2) (7). The structures of the different compounds have been determined by IR and NMR spectroscopic methods.
- Fandos, Rosa,Lanfranchi, Maurizio,Otero, Antonio,Pellinghelli, María Angela,Ruiz, M. José,Teuben, Jan H.
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p. 5283 - 5288
(2008/10/08)
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- (η5-C5Me5)2(Me)Ti-OC(Me)=CH2: titanium enolate or titanium alkoxide?
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While proton and carbon NMR spectroscopy suggest that (Cp*)2(Me)Ti-OC(Me)=CH2 (1, Cp* = η5-C5Me5) is a typical O-bound titanium enolate, this material does not exhibit typical enolate reactivity.Specifically, 1 does not react with either methyl iodide or with benzaldehyde.However, some reagents that are typically used in electrophilic attack of metal-alkyl or metal-alkoxide bonds do react with 1.In some cases the electrophile displaces the enolate moiety, while in other cases selectivity for substitution of the titanium-bound methyl group is displayed.Thus the reactivity of 1 is more typical of that expected from a titanium alkoxide or an alkyl titanium rather than a titanium enolate.The possible use of the (Cp*)2(Me)Ti moiety as a protecting group for ketones is discussed.
- Gibson, Charles P.,Bem, David S.
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- Structural features in electron-deficient (η-pentamethylcyclopentadienyl)titanium-diene complexes and their catalysis in the selective oligomerization of conjugated dienes
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A series of titanium-diene complexes of the type TiX(C5Me5)(s-cis-diene) (X = Cl, Br, I) was synthesized by the stoichiometric reaction of TiX3(C5Me5) with (2-butene-1,4-diyl)magnesium derivatives or by the reaction of TiX3(C5Me5) with RMgX (R = i-Pr, t-Bu, Et; X = Cl, Br, I) in the presence of a conjugated diene. All complexes were isolated as highly air-sensitive blue crystals in 30-60% yields. The complexes of unsubstituted and C(1) and/or C(4) alkyl-substitutecl dienes (butadiene, 1,3-pentadiene, 1,4-diphenylbutadiene) exhibit unique prone (endo) conformation while the complexes of C(2) and/or C(3) alkyl-substituted dienes (isoprene, 2,3-dimethylbutadiene, 2,3-diphenylbutadiene) prefer the supine (exo) conformation as revealed by the 1H and 13C NMR spectroscopic together with the X-ray diffraction analyses. The indirect 13C-13C coupling constants prove the pronounced η4-diene metal bonding nature for the prone titanium-diene complexes and substantial participation of bent metallacyclo-3-pentene structure for the supine complexes. TiCl(C5Me5)(s-cis-C4H6) of prone geometry crystallizes in space group P21/c with a = 6.999 (1) A?, b = 14.625 (3) A?, c = 13.842 (2) A?, β = 95.61 (2)°, and Z = 4. TiCl(C5Me5)(s-cis-1,4-diphenylbutadiene) belongs to orthorhombic space group Pnma with a = 8.260 (1) A?, b = 16.395 (3) A?, c = 16.308 (3) A?, and Z = 4. TiCl(C5Me5)(s-cis-2,3-diphenylbutadiene) of supine geometry crystallizes in space group C2/c with a = 22.049 (3) A?, b = 8.107 (2) A?, c = 26.869 (4) A?, β = 110.11 (1)°, and Z = 8. The extended Hu?ckel molecular orbital calculations reveal that the prone and supine structures of TiCl-(C5Me5)(C4H6) are energetically very close to each other. The nature of Ti-C4H6 bonding is discussed on the basis of population analysis. A low-valent species Ti(C5Me5)(isoprene) (g = 1.999 in EPR) generated by the reduction of TiCl(C5Me5)(isoprene) or on treatment of TiCl2(C5Me5) with (enediyl)magnesium catalyzes a highly selective (>99%) tail-to-head linear dimerization of isoprene and 2,3-dimethylbutadiene.
- Yamamoto, Hitoshi,Yasuda, Hajime,Tatsumi, Kazuyuki,Lee, Keonil,Nakamura, Akira,Chen, Jie,Kai, Yasushi,Kasai, Nobutami
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p. 105 - 119
(2008/10/08)
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- An investigation of the reaction of bis(cyclopentadienyl)titanium dichlorides with trimethylaluminum. Mechanism of an α-hydrogen abstraction reaction
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The reaction of Me3Al with Cp2TiCl2 and its derivatives has been studied. Synthetic procedures for the preparation of (C5R5)(C5H5)TiCl2 from (C5R5)Li and (C5H5)TiCl3 were developed, and sources of the major byproducts (C5H5)2TiCl2 and (C5R5)2TiCl2 are suggested. The derivatives studied were (C5R5) = C5H4SiMe3, 1,2,4-trimethylcyclopentadienyl, (CH3)5C5, indenyl, 1,3-Ph2C5H3, and (CH3)C5H4. All of these complexes reacted with 1 equiv of (CH3)3Al to produce Cp2Ti(CH3)Cl·Al(CH3)2Cl which would react further with a second equivalent of (CH3)3Al to yield a Cp2TiCH2AlMe2Cl derivative. The isotope effect for the parent reaction was 2.9. Substituents on the ring slowed the rate of methylene formation. A mechanism for α-hydrogen abstraction from a Ti-(CH3)Cl unit by an aluminum alkyl is proposed in which the Lewis acidic aluminum alkyl activates the titanium methyl group by complexation with the chlorine. The resulting aluminate then serves as a strong Lewis base to abstract the α-hydrogen.
- Ott, Kevin C.,DeBoer,Grubbs, Robert H.
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p. 223 - 230
(2008/10/08)
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