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  • 11
    Electronic Resource
    Electronic Resource
    ansa-Titanocene and -Zirconocene η2-Alkyne Complexes -Synthesis, Spectral Characteristics, and X-ray Crystal Structure (1996)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 959-962 
    Details
    ISSN: 0009-2940
    Keywords: ansa-Zirconocenes ; ansa-Titanocenes ; Alkyne complexes ; Pyridine ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reduction of the complex [(η5-C5H4)-ansa-(η5-C5H4)]TiCl2 with magnesium in the presence of Me3SiC2-SiMe3 in THF at room temperature gives the ansa-titanocone alkyne complex [(η5-C5H4)-ansa-(η5-C5H4)]Ti(η2-Me3SiC2-SiMe3) (ansa = Me2Si-O-SiMe2, 1). The similar pyridine-stabilized zirconium complexes could be obtained by analogous reactions and addition of pyridine: [(η5-C5H4)-ansa-(η5-C5H4)]Zr(L)(η2-Me3SiC2SiMe3) (ansa = Me2Si-O-SiMe2, L = pyridine: 2; ansa = SiMe2, L = pyridine: 3). All complexes were characterized by spectroscopic methods. An X-ray structure determination of complex 3 was conducted, and the data were compared to those of the complexes rac-(EB-HI)Zr(L)(η2-Me3SiC2SiMe3) [L = (S)-(-)-nicotine: 6, EBHI = ethylenebis(tetrahydroindenyl)] and Cp2Zr(py)(Me3SiC2-SiMe3).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19961290813
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  • 12
    Electronic Resource
    Electronic Resource
    Reactions of Lactams with Titanocene- and Zirconocene-Alkyne Complexes as Elemental Steps in Catalytic Anionic Ring-Opening Polymerization of Lactams (1996)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1281-1285 
    Details
    ISSN: 0009-2940
    Keywords: Zirconocenes ; Titanocenes ; N-Methyl-ε-caprolactam ; β-Propiolactam ; ε-Caprolactam ; Ring-opening polymerization ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Depending on the nature of the metal and the ring size, lactams react with titanocene and zircocene complexes of bis-(trimethylsilyl)acetylene Cp2Ti(Me3SiC2SiMe3) and Cp2Zr-(L)(Me3SiC2SiMe3) (L = Py, THF) to yield different products. In the reaction of Cp2Zr(Py)(Me3SiC2SiMe3) with N-methyl-€-caprolactam a simple ligand exchange reaction occurs and the complex Cp2Zr(Me3SiC2SiMe3)[O=H2)5] (1) was isolated. With β-propiolactam the alkenyl-amido complex Cp2)(SiMe3)][-NH2] (2) was obtained, which indicates that an agostic metal-hydrogen interaction has taken place. The reaction of Cp2Ti(Me3-SiC2SiMe3) with €-caprolactam gives after elimination of the alkyne and molecular hydrogen the first early transition metal complex with a deprotonated coordinated €-caprolactam in a η2-amidate bonding fashion (3). The obtained complexes were characterized by NMR spectra (1, 2) and crystal structure analysis (1-3) and discussed as elemental steps in anionic ring-opening polymerization of lactams catalyzed by metallocene-alkyne complexes.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19961291022
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  • 13
    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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  • 14
    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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  • 15
    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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  • 16
    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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  • 17
    Electronic Resource
    Electronic Resource
    Crown Thioether Chemistry: Novel Silver(I) Complexes of 1,3-Dithiole-Annelated 1,4,7-Trithiacyclononane (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 425-429 
    Details
    ISSN: 0009-2940
    Keywords: Silver complexes ; Crown compounds ; Thioethers ; 1,3-Dithioles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The coordination chemistry of two crown thioethers 2,5,8,10,12-pentathiabicyclo[7.3.0]dodeca-1)9)-ene-11-thione (L) and -11-one (L') with Ag1 has been investigated by structural methods. Both thioethers act as tridentate ligands coordinating the silver ion in a trigonal fashion. In the case L, the 11- thione sulfur is coordinated additionally by another silver ion, to yield a polymeric chain with a distorted-tetrahedral geometry about the metal ion. Despite differing only in its carbonyl chalcogen, L' forms six-coordinated, monomeric complexes.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300319
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  • 18
    Electronic Resource
    Electronic Resource
    Synthesis and Structure of Mononuclear Titanium Complexes Containing ansa-Aminopyridinato Ligands (1996)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1087-1091 
    Details
    ISSN: 0009-2940
    Keywords: ansa-Aminopyridinato ligands ; Strained amido ligands ; Titanium complexes ; Olefin polymerization ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of siloxane-bridged bis(2-aminopyridines) were synthesized from dichlorosiloxanes and 2-aminopyridines in the presence of a base via nucleophilic substitution reactions. They were used, after deprotonation, as dianionic (ansa-aminopyridinato) ligands to stabilize mononuclear titanium complexes with unusual coordination geometries. An X-ray crystal structure analysis of one of the ligands and of a titanium complex proved mononuclearity and provided information about the binding mode of this novel type of ligands. Ethylene polymerization studies showed low activity, remarkable differences between structurally related complexes, and broad molecular weight distributions. Sterically less demanding substituents and a high basicity of the ligand increase polymerization activity.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19961290917
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  • 19
    Electronic Resource
    Electronic Resource
    Nickel(0)-Komplexe fünfgliedriger Titana- und Zirconacyclocumulene als Zwischenstufen in der C-C-Bindungsspaltung disubstituierter ButadiineDer Max-Planck-Gesellschaft und dem Fonds der Chemischen Industrie danken wir für die finanzielle Unterstützung. (1996)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 108 (1996), S. 1175-1178 
    Details
    ISSN: 0044-8249
    Keywords: Butadiine ; C-C-Bindungsspaltungen ; Nickelverbindungen ; Titanverbindungen ; Zirkoniumverbindungen ; 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.19961081012
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  • 20
    Electronic Resource
    Electronic Resource
    Mixed Chloro(dialkylamido) Complexes of Zirconium and Hafnium (1995)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 621 (1995), S. 2021-2024 
    Details
    ISSN: 0044-2313
    Keywords: Amido complexes, zirconium, hafnium, X-ray crystal structure, reversible THF binding ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Gemischte Chloro-(Dialkylamido)-Komplexe des Zirconiums und HafniumsChloro-(Dialkylamido)-Komplexe des Types (R2N)2MCl2(THF)2 (R = Me, Et; M = Zr und R = Me; M = Hf) wurden in einer Metathesereaktion durch Zugabe einer äquimolaren Menge des M(NR2)4 zu einer Ethersuspension des entsprechenden MCl4 in Gegenwart von THF synthetisiert. Die Röntgenkristallstrukturanalysen von (Et2N)2ZrCl2 · (THF)2 (1 a) und (Me2N)2ZrCl2(THF)2 (1 b) ergaben gestörte oktaedrische Koordination, wobei die sterisch anspruchsvollen Dialkylamidliganden die Chlorid und die THF Liganden aus der idealen Koordinationsposition herausdrücken. Dynamische NMR-Untersuchungen belegen ein Gleichgewicht eines Komplexes mit gebundenem THF bei tiefen Temperaturen und Chloro-Amido-Komplexen an denen kein THF koordiniert bei höheren Temperaturen. Bei den „Tieftemperaturstrukturen“ wird eine übereinstimmung mit der entsprechenden Röntgenkristallstruktur vermutet.
    Notes: Chloro(dialkylamido) complexes of the type (R2N)2MCl2(THF)2 (R = Me, Et; M = Zr and R = Me; M = Hf) were synthesized in a conproportionation reaction by adding an equimolar amount of the corresponding M(NR2)4 to an ether slurry of MCl4 in the presence of THF. X-ray crystal structure determinations of (Et2N)2ZrCl2(THF)2 (1 a) and (Me2N)2ZrCl2 · (THF)2 (1 b) reveal a distorted octahedral coordination geometry where the sterically demanding dialkylamide ligands force the chloride and the THF ligands out of their ideal position. Dynamic NMR investigations indicate an equilibrium of complexes with coordinated THF at low temperature in accordance with the structure determined by X-ray crystallography and of chloro-amido complexes that do not bind THF (at higher temperature).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19956211207
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