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  • 1
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Substitution Reactions with Mixed Ligand Complexes of Nickel(0). I. Reactions with HeteroolefinesThe mixed ligand complexes (C2H4)Ni(PPh3)2 (A) and (COD) Ni(dipy) (B) react with “heteromonoolefines” L (carbonyl compounds, azomethines, azobenzene) by substitution forming LnNi(PPh3)2 or LnNi(dipy). In these complexes the heteromonoolefines are coordinated side-on as π-acid ligands. α-β-unsaturated carbonyl compounds, which are bonded by the C=C and not by the C=O function, take a special position.The olefines of A and B may also be substituted by diheterodiolefines L′(1,2-diketones and the corresponding diimines). However in the case of the reaction with the diimines not only compounds like L′Ni(PPh3)2 or L′Ni(dipy) but also bischelates like NiL′2 are easily formed by a further substitution.For the course of the substitution reactions the energy of the π*-orbital of the heteroolefine, which may be expressed by the polarographic half wave potential, is of a high importance. Heteroolefines with E1/2 〈 -2000 mV (acetone, ethyl benzoate) either do not react with the mixed ligand complexes A and B or the substitution requires special conditions (propanal). Relations and differences of B and (dipy)NiEt2 as to their reactivities with heteroolefines are discussed.
    Notes: Die Gemischtligand-Komplexe (C2H4)Ni(PPh3)2 (A) bzw. (COD) Ni(dipy) (B) reagieren mit “Heteromonoolefinen” L (Carbonylverbindungen, Azomethine, Azobenzol) unter Substitution zu LnNi(PPh3)2 bzw. LnNi(dipy). Die Heteromonoolefine koordinieren in diesen Komplexen “side-on” als π-Säure-Liganden. Eine Sonderstellung nehmen α, β-ungesättigte Carbonyl-verbindungen (Acrolein, Dibenzylidenaceton) ein, die nicht über die C=O-, sondern über die C=C-Gruppierung gebunden werden.Die Olefine in A und B können auch durch Diheterodiolefine (1,2-Diketone und die zugehörigen Diimine) substituiert werden (Bildung von L′Ni(PPh3)2 bzw. L′Ni(dipy)). Im Falle der Umsetzung mit den Diiminen entstehen jedoch leicht durch weitere Substitution die vierfach-koordinativen Bischelate NiL′2.Für den Ablauf der Substitutionsreaktionen ist die Lage des π*-Orbitals der Heteroolefine von Bedeutung, die im polarographischen Halbstufenpotential ihren Ausdruck findet. Heteroolefine mit E1/2 〈 -2000 mV (Aceton, Benzoesäureäthylester) reagieren nicht mit den betrachteten Gemischtligandkomplexen oder nur unter verschärften Bedingungen (Propionaldehyd). Es werden Analogien und Unterschiede in der Reaktivität von B bzw. (dipy)NiEt2 gegenüber Heteroolefinen diskutiert.
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  • 2
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Nickel(0) Complexes with the Donor Set N2P2Mixed ligand complexes of the type (dipy)Ni(PR3)2 are stabil, provided the n-donor α,α′ -dipyridyl is combined with a tertiary phosphine or a phosphite acting as a π-acceptor. They may be prepared from (R3P)2Ni(C2H4) and dipy, from (dipy) Ni(COD) and PR3, or from (dipy) Ni(C2H5)2 and PR3. Starting with [(C6H11)3P]2Ni(C2H4) or (dipy)Ni(COD) the synthesis of the complex (dipy)Ni[P(C6H11)3]2 containing only n-donor ligands, failed. By the reaction of (dipy)Ni(C2H5)2 with (C6H11)3P the olefin complex [(C6H11)3P]2Ni(C2H4) was formed.
    Notes: Gemischtliganden-Komplexe des Typs (dipy)Ni(PR3)2 sind dann stabil, wenn dem n-Donator α,α′-Dipyridyl ein Phosphan bzw. Phosphit mit π-Akzeptorfunktion als Zweitligand gegenübersteht. Sie können aus (R3P)2Ni(C2H4) und dipy, aus (dipy) Ni(COD) und PR3 oder aus (dipy)Ni(C2H5)2 und PR3 dargestellt werden.Die Synthese des Komplexes (dipy)Ni[P(C6H11)3]2, in dem nur n-Donatoren als Liganden vorlägen, gelang, wenn von [(C6H11)3P]2Ni(C2H4) oder (dipy)Ni(COD) ausgegangen wurde, nicht. Die Reaktion von (dipy) Ni(C2H5)2 mit (C6H11)3P führt zu [(C6H11)3P]2Ni(C2H4).
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  • 3
    ISSN: 0365-9631
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 4
    ISSN: 0365-9631
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
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  • 5
    ISSN: 0365-9631
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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