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  • 1
    ISSN: 1434-1948
    Keywords: N-ligands ; Yttrium ; Samarium ; Ring-opening polymerization ; Lactones ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of one equivalent of dilithiated O(SiMe2-Ap-H)2 [Ap-H = -N(2-amino-4-methylpyridine)] (1), generated in situ, with LnCl3 (Ln = Y, Sm) in THF affords O(SiMe2-Ap)2YCl(THF)2 (2) or O(SiMe2-Ap)2SmCl(THF)3 (3). In contrast, the reaction of one or two equivalents of dilithiated 1, again generated in situ, with LaBr3 in THF affords O(SiMe2-Ap)2)2LaLi(THF)3 (4). An X-ray structural analysis of 2 and 3 reveal the O(SiMe2-Ap)2- ligand to bind in a planar tetradentate manner. Equivalent Sm-N distances in 3 indicate a delocalized binding mode. Compound 2 reacts with Bu4NBH4, NaBH4 or LiCH(SiMe3)2 to give the corresponding “ate” complexes O(SiMe2-Ap)2Y(BH4)Cl(THF) Bu4N (5), O(SiMe2-Ap)2Y(BH4)2Na(THF)2 (6) and O(SiMe2-Ap)2Y(CH(TMS)2)2Li(THF)3 (7), respectively. The steric demand of the O(SiMe2-Ap)2- ligand is not large enough to stabilize monoalkyl or monoborohydride complexes. Complex 4 has been used as an initiator for the ring-opening polymerization of ε-caprolactone or δ-valerolactone. In both cases an almost linear relation between the monomer-to-initiator ratio and the molecular weight of the obtained polyester is observed. By conducting the polymerization in neat ε-caprolactone at room temperature a solid polyester block is formed after 3 min (300000 g·mol-1, Mw/Mn 2.3).
    Additional Material: 2 Ill.
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  • 2
    ISSN: 0044-2313
    Keywords: Ferrocene ; aminopyridinato ligands ; titanium complexes ; bimetallic complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Ferrocen-verbrückte „Amidoliganden“; Synthese von bimetallischen Bis(aminopyridinato)-Komplexen des TitansDer neuartige, Ferrocen-verbrückte „Aminopyridinligand“ fc(Me2SiApH)2 (3). fc(Me2SiApH)2 = 1,1′Bis{[(N-4-methylpyridin-2-yl)amino]dimethyIsilyl}ferrocen, wurde durch die Umsetzung von 1,1′-Bis(chlorodimethylsilyl)ferrocen (1) mit dem Natriumsalz von 4-Methyl-2-aminopyridin in Hexan synthetisiert, Verbindung 1 ist durch die Reaktion von 1,1′-Dilithioferrocen mit einem vierzigfachen Überschuß von Me2SiCl2 zugänglich. Durch Umsetzung von 3 mit jeweils einem Äquivalent Ti(NMe2)4 bzw. CTTi(NMe2)3 wurden die bimetallischen Titankomplexe fc(Me2SiAp)2Ti(NMe2)2 (4) und fc(Me2SiAp)2Ti(NMe2)CI (5), erhalten. Die Ergebnisse der Röntgenkristallstrukturanalyse von 3 werden diskutiert.
    Notes: The ferrocene based aminopyridine “ligand” fc(Me2SiApH)2 (3), fc(Me2SiApH)2 = 1,1′-bis{[(N-4-methylpyridin-2-yl)amino]dimethylsilyl}ferrocene, has been synthesized by the reaction of 1,1′-bis(chlorodimethylsilyl)ferrocene (1) with the sodium salt of 4-methyl-2-aminopyridine in hexane. Compound 1 is accessible by the reaction of 1,1′-dilithioferrocene with a fortyfold excess of Me2SiCl2. The reactions of 3 with one equiv of Ti(NMe2)4 or ClTi(NMe2)3, resp. afford the corresponding bimetallic titanium complexes fc(Me2SiAp)2Ti(NMe2)2 (4) or fc(Me2SiAp)2Ti(NMe2Cl (5)), resp. The crystal structure of 3 is reported.
    Additional Material: 1 Ill.
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  • 3
    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.
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  • 4
    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.
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