Crystal structure of an organometallic complex with titanium-carbon .sigma. bonds. Tetrabenzyltitanium

Bassi, I. W.; Allegra, Giuseppe; Scordamaglia, R.; Chioccola, G.

doi:10.1021/ja00744a049

Cited by 100 publications

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“…The Ti-< distances for t h~ a-bonded phenyl rings were found to be 2.21(1) and 2.25 A in 1. These T i L C distances are comparable to those foundoin Cp2TiPh2 (2.27(1) A) (13) and in (indenyl)2TiMe2 (2.2 l(2) A) (14) and ye; are considerably longer than those found in TiBz4 (2.14(1) A) (15). The angle between the planes of the two phenyl rings is 81.9".…”

Section: Structural Studysupporting

confidence: 76%

Bimetallic titanium alkoxides: synthesis and structure of Cp₂Ti(Ph)(μ-OCH₂C(CH₃)₂CH₂O)(Ph)TiCp₂; a precursor to macrocyclic metallocene derivatives

Nadasdi¹,

Stephan²

1991

Can. J. Chem.

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The reaction of Cp2TiPh2 with 2,2-dimethylpropane-1,3-diol proceeds with the evolution of benzene affording the bimetallic titanocene alkoxide species Cp2Ti(Ph)(p-OCH2C(CH3)2CH20)(Ph)TiCpz, 1. Complex 1 crystallizes in the monclinic space group Cc with a = 25.448(7) A, b = 8.483(s) A, c = 14.512(3) A, P = 101.52(2)", Z = 4, and V = 3070(1) A3. The structure was refined employing 1471 data with Fo > 3uF0 and 138 variables to R values of R = 0.0588 and R,,, = 0.0828. the dimeric nature of 1 is confirmed. The coordination spheres of the two Ti centres are pseudo-tetrahedral. The T i 4 u bonds were found to be 2.21(1) and 2.25(1) A. Although the phenyl substituents are directed towards each other, steric effects appear to be overcome by the approximately perpendicular orientation of the phenyl rings (in fact the angle between the planes is 81.9"). The Ti ... Ti separation in 1 is 6.725 A. The implications of the preparation of 1 regarding the mechanism of formation of early metal macrocyclic compounds are discussed. In addition, the ramifications for the synthesis of dissymmetric early metal macrocycles are considered.Key words: titanium alkoxides, alkoxide bridged, structure. Introduction Titania or zirconia are often employed as support materials for heterogeneous catalysts (1). These supports may act simply as a dispersent for the late metal centers or may play an active role in the catalytic cycle. In the latter case, such participation gives rise to the phenomenon known as strong metal-support interactions (SMSI) (1). Activation of substrate molecules by a Lewis acidic, early metal and a late metal center may account for the observed effects. We and others have investigated homogeneous systems in which early and late metals are linked in close proximity by bridging Iigands (2). Such heterobimetallics are of interest both as models for the heterogeneous catalyst systems and because of their potential as catalysts in their own right. Fewer studies have focused on simple complexes of Ti or Zr that might model the Lewis acidic, early metal centers of titania or zirconia. Several groups (3-3, have reported the syntheses and reaction chemistry of a variety of early metal alkoxide complexes. The similarity of metal-alkoxide species to metal oxides and the propriety of such species as models for metal-oxide surfaces have been considered by others (3). Much of the work to date has focused on systems in which sterically demanding alkoxy or aryloxy ligands inhibit oligomerization and yield mononuclear early metal compounds (4, 5). In our 'A complete set of supplementary material may be purchased from the Depository of Unpublished Data, CISTI, National Research Council of Canada, Ottawa, Ont., Canada KIA 0S2. initial investigations in this area, we described the specific formation of bimetallic macrocyclic Zr-alkoxide species via the reaction of dimethylzirconocene with diols (Scheme 1) (6).In this report we describe the product of the related reaction of Cp2TiPh2 with 2,2-dimethylpropanediol, i.e., Cp2Ti(Ph)(p-0CH2C(CH3)2...

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Section: Structural Studysupporting

confidence: 76%

Bimetallic titanium alkoxides: synthesis and structure of Cp₂Ti(Ph)(μ-OCH₂C(CH₃)₂CH₂O)(Ph)TiCp₂; a precursor to macrocyclic metallocene derivatives

Nadasdi¹,

Stephan²

1991

Can. J. Chem.

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“…The substantial η 3 coordination of the benzyl group is quite similar to the way of coordination of the benzyl groups in the X-ray structure of the Ti(CH 2 Ph) 4 complex. 70 The benzene molecule, instead, is substantially η 6 coordinated to the metal, as suggested by the short (∼2.5 Å) Ti-C(benzene) distances. From an energetical point of view, structure 1b is favored relative to structure 1a by 12 kJ mol -1 only.…”

Section: Resultsmentioning

confidence: 99%

Theoretical Study of Syndiospecific Styrene Polymerization with Cp-Based and Cp-Free Titanium Catalysts. 1. Mechanism of Chain Propagation

Minieri¹,

Corradini²,

Zambelli³

et al. 2001

Macromolecules

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A theoretical study of the mechanism of styrene polymerization with models based on the CpTiP + (P ) polymeryl) species is presented. The styrene-free CpTiCH2Ph + species, with a coordinated benzene molecule to simulate the solvent, is characterized by two minimum geometries with different hapticities of coordination of the benzyl group. The η 3 coordination is more stable than the η 7 coordination by 12 kJ mol -1 . Substitution of the solvent molecule by styrene leads to coordination intermediates which are also characterized by different hapticities of the styrene. When the benzyl group is η 7 coordinated the styrene is η 2 coordinated, while in the case of η 3 coordination of the benzyl group, styrene is η 4 coordinated. All these coordination intermediates are of similar energy and are separated by low energy barriers. Insertion can occur with a relatively small energy barrier, 47 kJ mol -1 , from a coordination intermediate presenting a η 3 coordinated growing chain, and a η 4 -coordinated styrene molecule. The products of the insertion reaction are characterized by a backbiting of the aromatic ring of the penultimate unit. As for the role of Ti II active species, our calculations suggest that neutral active species of the type CpTi II P should be not able to promote styrene polymerization, whereas cationic active species of the type (benzene)Ti II P + should be able to promote styrene polymerization, although the latter species should be less active than species of the type CpTi III P + .

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“…[23] According to theoretical calculations, homoleptic, unsolvated ™TiMe 4 ∫ should not exist in the presence of Et 2 O, which is usually the solvent chosen to prepare it. [31] As far as we know, the only structurally characterized [TiR 4 ] species is [Ti(CH 2 Ph) 4 ]; [32] it is now generally accepted, however, that the benzyl group is not an innocent ligand, being prone to involve the p-electron density of the phenyl ring to give (h [27] and [Ti{CH(SiMe 3 ) 2 } 3 ]. [34] Considering the lack of structural information currently available for homoleptic s-organotitanium(iii) and titanium(iv) compounds, it would be interesting to obtain reliable data on the molecular geometry of this important class of compounds.…”

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confidence: 99%

Synthesis and Characterization of Pentachlorophenyl–Metal Derivatives with d⁰ and d¹⁰ Electron Configurations

Ara

Forniés

García‐Monforte

et al. 2004

Chemistry A European J

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By reaction of [TiCl(3)(thf)(3)] with LiC(6)Cl(5), the homoleptic organotitanium(III) derivative [Li(thf)(4)][Ti(III)(C(6)Cl(5))(4)] (1) has been prepared as a paramagnetic (d(1), S = 1/2, g(av) = 1.959(2)), extremely air-sensitive compound. Oxidation of 1 with [N(C(6)H(4)Br-4)(3)][SbCl(6)] gives the diamagnetic (d(0)) organotitanium(IV) species [Ti(IV)(C(6)Cl(5))(4)] (2). Compounds 1 and 2 are also electrochemically related (E(1/2) = 0.05 V). The homoleptic, diamagnetic (d(10)) compounds [N(PPh(3))(2)][Tl(C(6)Cl(5))(4)] (3) and [Sn(C(6)Cl(5))(4)] (4) have also been prepared. Nearly tetrahedral environments have been found for the d(0), d(10), and d(1) metal centers in the molecular structures of compounds 2-4 as well as in that of [Li(thf)(2)(OEt(2))(2)][Ti(III)(C(6)Cl(5))(4)].CH(2)Cl(2) (1') (X-ray diffraction). The reaction of the heavier Group 4 metal halides, MCl(4) (M = Zr, Hf) with LiC(6)Cl(5) in the presence of [NBu(4)]Br gives, in turn, the heteroleptic species [NBu(4)][M(C(6)Cl(5))(3)Cl(2)] (M = Zr (5), Hf (6)). Compounds 5 and 6 are isomorphous and isostructural, with the metal center in a trigonal-bipyramidal (TBPY-5) environment defined by two axial Cl ligands and three equatorial C(6)Cl(5) groups (X-ray diffraction). No redox features are observed for compounds 3-6 in CH(2)Cl(2) solution between -1.6 and +1.6 V.

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Crystal structure of an organometallic complex with titanium-carbon .sigma. bonds. Tetrabenzyltitanium

Cited by 100 publications

References 0 publications

Bimetallic titanium alkoxides: synthesis and structure of Cp₂Ti(Ph)(μ-OCH₂C(CH₃)₂CH₂O)(Ph)TiCp₂; a precursor to macrocyclic metallocene derivatives

Bimetallic titanium alkoxides: synthesis and structure of Cp₂Ti(Ph)(μ-OCH₂C(CH₃)₂CH₂O)(Ph)TiCp₂; a precursor to macrocyclic metallocene derivatives

Theoretical Study of Syndiospecific Styrene Polymerization with Cp-Based and Cp-Free Titanium Catalysts. 1. Mechanism of Chain Propagation

Synthesis and Characterization of Pentachlorophenyl–Metal Derivatives with d⁰ and d¹⁰ Electron Configurations

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Crystal structure of an organometallic complex with titanium-carbon .sigma. bonds. Tetrabenzyltitanium

Cited by 100 publications

References 0 publications

Bimetallic titanium alkoxides: synthesis and structure of Cp2Ti(Ph)(μ-OCH2C(CH3)2CH2O)(Ph)TiCp2; a precursor to macrocyclic metallocene derivatives

Bimetallic titanium alkoxides: synthesis and structure of Cp2Ti(Ph)(μ-OCH2C(CH3)2CH2O)(Ph)TiCp2; a precursor to macrocyclic metallocene derivatives

Theoretical Study of Syndiospecific Styrene Polymerization with Cp-Based and Cp-Free Titanium Catalysts. 1. Mechanism of Chain Propagation

Synthesis and Characterization of Pentachlorophenyl–Metal Derivatives with d0 and d10 Electron Configurations

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Bimetallic titanium alkoxides: synthesis and structure of Cp₂Ti(Ph)(μ-OCH₂C(CH₃)₂CH₂O)(Ph)TiCp₂; a precursor to macrocyclic metallocene derivatives

Bimetallic titanium alkoxides: synthesis and structure of Cp₂Ti(Ph)(μ-OCH₂C(CH₃)₂CH₂O)(Ph)TiCp₂; a precursor to macrocyclic metallocene derivatives

Synthesis and Characterization of Pentachlorophenyl–Metal Derivatives with d⁰ and d¹⁰ Electron Configurations