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  • 1
    Electronic Resource
    Electronic Resource
    Stability of Bridged and Unbridged η2-Alkyne-titanocene and -zirconocene Complexes - Influence of Metals, Alkyne Substituents, Cp Substitution and Additional Ligands (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 419-424 
    Details
    ISSN: 1434-1948
    Keywords: Alkyne complexes ; Titanium ; Zirconium ; Coordination mode ; Metallacycles ; Cyclopentadienes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of metals, alkyne substituents, Cp substitution and additional ligands on the stability of bridged and unbridged η2-alkyne-titanocene and -zirconocene complexes has been investigated. The reduction of the complex [(η5-C5H4)-SiMe2-(η5-C5H4)]TiCl2 with magnesium in the presence of tolan (PhC2Ph) does not give the expected alkyne-titanocene complex [(η5-C5H4)-SiMe2-(η5-C5H4)]Ti(η2-PhC2Ph) but by coupling of two tolan molecules the corresponding titanacyclopentadiene [(η5-C5H4)-SiMe2-(η5-C5H4)]TiC4Ph4 (1) was obtained. In the analogous reaction with Me3SiC2SiMe3 the stable η2-alkyne complex without additional ligands [(η5-C5H4)-SiMe2-(η5-C5H4)]Ti(η2-Me3SiC2SiMe3) (2) was formed, due to the sterical influence of the alkyne substituents. The compounds without additional ligands (thi)2Ti(η2-PhC2Ph) (3) and (thi)2Ti(η2- Me3SiC2SiMe3) (5) were isolated from the unbridged titanocene complex (thi)2TiCl2 (thi = tetrahydroindenyl). Two equivalents of complex 3 reacted with one equivalent of water to yield the dimeric alkylidene-μ-oxo complex [(thi)2Ti(CPh=CHPh)]2(μ-O) (6). The reaction of the unbridged zirconocene compound (thi)2ZrCl2 gave the alkyne complex (thi)2Zr(THF)(η2-Me3- SiC2SiMe3) (7) which is stabilized by THF. At higher temperature THF was eliminated from the orange complex 7 forming the green complex (thi)2Zr(η2-Me3SiC2SiMe3). This behaviour was investigated in detail using NMR spectroscopy and compared to similar complexes such as Cp2Zr(η2-Me3SiC2SiMe3) (not stable without THF), (ebthi)2Zr(η2-Me3SiC2SiMe3) (ebthi = ethylenebistetrahydroindenyl; stable without THF) and Cp*2Zr(η2-Me3SiC2SiMe3) (Cp* = pentamethyl-Cp, stable without THF). All complexes were characterized by spectroscopic methods. X-ray structural determinations were conducted for the complexes 1, 3 and 7. Compound 3 is the first example of a structurally characterized tolan-titanocene complex without additional ligands.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Untypical Regioselectivity of Carbon Dioxide Coupling with Titanocene Complexes of Phenyl(trimethylsilyl)acetylene by Using the meso-1,2-Ethylene-1,1′-bis(η5-tetrahydroindenyl) Ligand System (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1495-1502 
    Details
    ISSN: 1434-1948
    Keywords: Alkyne complexes ; Titanium ; ansa-Metallocenes ; Carbon dioxide fixation ; C-C coupling ; Metallacycles ; Regioselectivity ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of [meso-(ebthi)TiCl2] [ebthi = 1,2-ethylene-1,1′-bis(η5-tetrahydroindenyl)] with magnesium in the presence of the alkynes Me3SiC≡CSiMe3 and PhC≡CSiMe3 resulted in the formation of the complexes [meso-(ebthi)Ti(η2-Me3SiC2SiMe3)] (1) and [meso-(ebthi)Ti(η2-PhC2SiMe3)] (2a and 2b), which were isolated and then characterized by their NMR spectra. Due to incomplete reduction the TiIII complex [meso-(ebthi)Ti(THF)Cl] (3) was also obtained as a by-product of these reactions. By insertion into the Ti-CPh bond carbon dioxide reacted with the titanacyclopropene structure of the alkyne complex [meso-(ebthi)Ti(η2-PhC2SiMe3)] (2a), with untypical regioselectivity to yield the α-silyl-substituted meso-(ebthi)titanafuranone 6a. In the analogous reactions of the complexes [(thi)2Ti(η2-PhC2SiMe3)] (thi = η5-tetrahydroindenyl), [rac-(ebthi)Ti(η2-PhC2SiMe3)], and [Cp*2Ti(η2-PhC2SiMe3)] with carbon dioxide typical regioselectivity (insertion into the M-CSi bond of the titanacyclopropene) was observed, yielding the β-silyl-substituted titanafuranones 7, 8a, and 9. These results show that insertion of carbon dioxide into the M-C bond of the titanacyclopropene structure of the alkynemetallocene complexes is governed by the substitution pattern of the alkyne and the steric enviroment around the metal center. The complexes 3, 6a, and 7 were investigated by X-ray crystal structure analysis.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Ligand- Substrate Communication in Group 4 Aminopyridinato Complexes (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 789-794 
    Details
    ISSN: 0009-2940
    Keywords: Agostic interactions ; Ligand effects ; Titanium ; Zirconium ; Aminopyridinato ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tris(aminopyridinato) zirconium and ansa-aminopyridinato titanium complexes have been sythesized. The reaction of (TMS-APy)3-Zr-Cl (4-methyl-2-trimethylsilyl-aminopyridine=TMS-APy-H) with trimethylsilylbutadiynyl lithium generated in situ affords (TMS-APy)3—Zr—C≡C—C≡C—TMS (1). (TMS-apy)3-Zr-Me2 (2). Compound 2 shows an agostic interaction of the dimethylamido moiety. The reaction of Ti(NMe,2),4 with silox(Apy-H)21,3-di(4′-picolin-2′-yl-amino)-1,1,3,3-tetraisopropyldisiloxane=silox (APy-H)2] gives rise to silox(Apy)2-Ti-(NMe2)2-Ti-[NMe,2)2 (3). Complex 3 reacts with ε-caprolactam to form a caprolactamato complex (4). X-ray crystal structure analyses of 1, 2, 3 and 4 are reported. The complexes 1, 2, 3 and 4 may be considered to be strained donor-functionalized amido(metal) complexes due to the η2 binding mode of the ligand cores, TMS-APy and silox(APy)2, to meet the requirements of the ancillary coordinated substrates is observed. Thus, aminopyridinato complexes seem to be valuable model compounds for investigations of ligand-substrate communications in early transition metal chemistry.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300618
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    Paper (German National Licenses)
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