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  • Zirconium  (3)
  • Silanes, sterically congested  (2)
  • Titanocene  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Geminal di(hypersilyl) Compounds  -  the Synthesis and Structure of Bis[tris(trimethylsilyl)silyl]methanol (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1709-1714 
    Details
    ISSN: 0009-2940
    Keywords: Silicon ; Strained molecules ; Silanes, sterically congested ; Tris(trimethylsilyl) silanes ; Silenes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tris(trimethylsilyl)silyllithium (1) reacts with methyl formate in diethyl ether (molar ratio 2:1) to give 1,2-di(hypersilyl)- ethylene 13. The formation of 13 proceeds through the intermediates formyl tris(trimethylsilyl)silane (4) and lithium bis-[tris(trimethylsilyl)silyl]methoxide (5). In diethyl ether, the alkoxide 5 spontaneously eliminates lithium trimethylsilanolate thereby generating 1,1-bis(trimethylsilyl)-2-[tris(trimethylsilyl)silyl]silene (9), which undergoes a formal [2+2] cycloaddition with the carbonyl compound 4 to afford 13. This was verified by crossover experiments. In Pentane, the alkoxide 5 is moderately stable. Thus, the intermediate 5, prepared by reaction fo 1 with tert-butyl formate in pentane. was protonated with water to give the di(hypersilyl)methanol 6 in good yield. The structure of 6 in good yield. The structure of 6 was elucidated by an X-ray crystal structure analysis, which expectedly revealed tremendous distortions of the molecular skeleton. Thus, the spatial demand of the two extended hemispherical (Me3Si)3Si groups forces a widening of the Si-C-Si angle at the central sp3 carbon atom to a value of 135.5°.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971301123
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  • 2
    Electronic Resource
    Electronic Resource
    The First Titanacyclic Five-Membered Cumulene. Synthesis, Structure, and Reactivity (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 967-971 
    Details
    ISSN: 0009-2940
    Keywords: Titanocene ; Diyne ; Cumulene ; Titanacyclopentadiene ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The first five-membered titanacyclic cumulene (5) was prepared by treatment of the titanocene generator Cp2Ti(Me3SiC2SiMe3) with the di-tert-butylbutadiyne in a molecular one-to-one ratio. The reaction of 5 with “Cp2Zr” or of the analogous complex with “Cp2Ti” leads to cleavage of the central C-C bond in the metallacyclocumulene complexes to afford the same product, the heterodimetallic ρ, π,-alkynyl-bridged titanocene-zirconocene complex Cp2Zr(μ-η1η2-C≡CtBu)Cp2Ti(μ-η1η2-C≡CtBu) (6), in which each alkynyl group is π-bonded to one and π-bonded to the other metal as shown by X-ray diffraction studies. In solution the two alkynyl groups become equivalent. The coupling reaction of “Cp2Ti” with bis(trimethylsilyl)butadiyne in a one-to-two molecular ratio leads to the unsymmetrically substituted titanacyclopentadiene (7).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951281002
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  • 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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  • 4
    Electronic Resource
    Electronic Resource
    Ring-Enlargement and Ring-Opening Reactions of Benzoxazole, Thiazoles, and Benzisoxazole by Zirconocene-Alkyne Complexes (1996)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 207-211 
    Details
    ISSN: 0009-2940
    Keywords: Zirconocene ; Titanocene ; Benzoxazoles ; Thiazoles ; Benzisoxazoles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Zirconocene alkyne complexes Cp2Zr(L)(Me3SiC2R) (L = Py, THF; R = SiMe3 tBu) react with heterocyclic compounds like benzoxazole and related thiazoles to yield ring-expanded adducts (1-3) and (4, 5) by formal C-X (X = O, S) bond cleavage and coupling with the coordinated alkyne. In the case of benziso-xazole, the alkyne is not coupled but eliminated, and with ring-enlargement of the benzisoxazole a N-bridged dimer (6) is formed. The obtained complexes 1, 3, and 6 were characterized by NMR spectra and crystal structure analysis.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19961290214
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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Geminal Bis(hypersilyl) Compounds - The Reaction of Tris(trimethylsilyl)silyllithium with Dialkyl(chloromethylene)ammonium Chlorides (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 21-26 
    Details
    ISSN: 1434-1948
    Keywords: Silicon ; Silanes, sterically congested ; Tris(trimethylsilyl)silanes ; (Chloromethylene)ammonium chlorides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tris(trimethylsilyl)silyllithium (1) reacts with dialkyl(chloromethylene)ammonium chlorides (molar ratio 2:1) to give the (dialkylamino)bis(hypersilyl)methanes [(Me3Si)3Si]2CHNR2 (5a-c; a: R = Me, b: R = Et, c: R2 = [CH2]5). Due to the extreme bulkiness of the hemispherical (Me3Si)3Si substituents, the structures of these geminal bis(hypersilyl) derivatives are characterized by tremendous distortions of their molecular skeletons. This was confirmed by X-ray structural analyses of 5a and 5c, which revealed considerable elongations of the central Si-C bonds (5a: 2.01 and 1.95 Å; 5c: 1.99 and 1.97 Å) and an extreme widening of the Si-C-Si angles at the central sp3-carbon atoms (5a: 132.6°; 5c: 128.7°). By concentrated sulfuric acid, 5a is converted to give, after hydrolysis, the silanol (Me3Si)2Si(OH)-CH2Si(SiMe3)3 (13). The formation of 13 is discussed as proceeding through the transient silene (Me3Si)2Si=CHSi(SiMe3)3 (11), generated by a formal (dimethylamino)trimethylsilane elimination from 5a according to an acid-induced sila Peterson mechanism.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Doppelte C-C-Einfachbindungsaktivierung und -spaltung bei der Umsetzung von Octatetrainen mit Titanocen- und ZirconocenkomplexenProfessor Jörg Lorberth zum 60. Geburtstag gewidmetDer Max-Planck-Gesellschaft und dem Fonds der Chemischen Industrie danken wir für die finanzielle Unterstützung. (1997)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 109 (1997), S. 2728-2730 
    Details
    ISSN: 0044-8249
    Keywords: Alkinkomplexe ; C-C-Aktivierung ; Octatetraine ; Titan ; Zirconium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19971092314
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