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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1795-1799 
    ISSN: 0009-2940
    Keywords: Carbonyl complexes ; Rhenium complexes ; Alkoxy carbene, structure of ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metal Carbonyl Syntheses, XXI. - Straightforward Synthesis of a Synthetically Useful Alkoxy(carbonyl)metallateAnionic methoxy complexes are formed upon carbonylation of ammonium perrhenate in methanol at 230-240°C. Thus, the dinuclear ionic complex [N(CH3)4][Re2(CO)6(μ-OCH3)3] (2) results in 80% yield at CO pressures of ca. 100 bar, while the trinuclear derivative [N(CH3)4][Re3(CO)9(μ3-OCH3)3(μ3-OCH3)] (3) is due to lower pressure conditions (ca. 50 bar); 2 yields the bis(carbene) complex 4 of formula fac-Re(CO)3L2I upon treatment with a bis(imidazolium) iodide, thus demonstrating that carbonylrhenium chemistry not necessarily depends on the availability of Re2(CO)10.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 1971-1974 
    ISSN: 0009-2940
    Keywords: Alkylidyne ligands ; Rhenium complexes ; Metal-metal multiple bonds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Multiple Bonds Between Main-Group Elements and Transition Metals, LXXXII.  -  Dinuclear p-Benzylidyne Complexes Having a Double Bond between Rhenium AtomsThe dialkylrhenium(V) complex (η5-C5Me5)Re(=O)(CH2Ph)2 (3) reacts with the organotitanium reagents (η5-C5H5)TiX3 (X = Cl, Br) to yield the dinuclear rhenium(IV) complexes (η5C5Me5)2 Re2X3(CC6H5) (4a, b). According to a single-crystal X-ray diffraction analysis, 4a′ (C5Me4Et in place of C5Me5) represents one of the few known examples of μ-alkylidyne complexes that have metal-to-metal multiple bonds. The molecule of C2 symmetry has a planar four-membered Re,Cl,Re′,C-ring geometry and two trans-oriented sets of ligands. Very small angles at the bridging chloro ligand and alkylidyne carbon atom result from the short metal-metal distance (double bond).
    Additional Material: 1 Ill.
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  • 3
    ISSN: 0009-2940
    Keywords: CH Acidity ; Rhenium complexes ; Allylidene ; Butatriene ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: α-CH Acidity of Allylidene Complexes: Organorhenium Derivatives of 1,2,3-Butatriene by Dehydrochlorination of Rhena(V) Allylidenes. Synthesis and StructureThe rhena(V) allylidene complex (η5-C5Me5)ReCl2 [η1:η3-(CH3)-CC(Cl)CH2] (2) is quantitatively converted into the novel organorhenium 1,2,3-butatriene derivative (η5-C5Me5)ReCl2[η3-H2CC(C5H5N)CCH2] (3) by lithium hydroxide in the presence of excess pyridine. This result shows so far not investigated CH acidity of methyl groups, that are substituting π-bonded allylidene frameworks at the α-position. According to an X-ray structure analysis, the coordination geometry of the 1,2,3-butatriene ligand is very similar to related allyl complexes of the (η5-C5Me5)ReCl2 fragment.
    Notes: Der Rhena(V)-allyliden-Komplex (η5-C5Me5)ReCl2 [η1:η3-(CH3)-CC(Cl)CH2] (2) wird durch Lithiumhydroxid in Gegenwart von überschüssigem Pyridin quantitativ zu dem neuartigen rhenium-organischen 1,2,3-Butatrien-Derivat (η5-C5Me5)ReCl2[η3-H2CC(C5H5N)CCH2] (3) dehydrohalogeniert. Dieses Ergebnis weist auf die bisher nicht beachtete CH-Acidität von Methylgruppen hin, die ein π-gebundenes Allyliden-Gerüst α-ständig substituieren. Einer Röntgenstrukturanalyse zufolge ist der von 1,2,3-Butatrien abgeleitete Ligand allylartig an das (η5-C5Me5)ReCl2-Fragment gebunden.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0009-2940
    Keywords: Palladium ; Phosphanes ; Catalysis ; Cyclopalladation reaction ; Metallacycles ; CH activation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to synthesize chiral palladacycles for stereoselective C-C coupling reactions we studied the cyclopalladation of P-chiral phosphanes 2 and 3. New palladium complexes of the type L2PdX2 (6, 8) and LXPd-μ-X2-PdXL (5, 9, X = Cl; L = 2, 3) were isolated. A detailed study of the reactivity of all intermediates towards cyclopalladation proved the mechanism of cyclometalation reactions of o-tolylphosphanes for the first time. Different deuteration experiments clearly demonstrated the higher reactivity of dimeric palladium complexes towards metalation compared to monomeric species. In agreement with this observation only 5 and 9 gave the cyclopalladated products 4 and 10 as revealed by FAB mass spectrometric investigations. Under the described reaction conditions the synthesis of the corresponding palladacycles 4, 10 is not possible because cyclometalation is a reversible process with LXPd-μ-X2-PdXL as thermodynamic more stable products. The results demonstrate the importance of free coordination sites on the metal atom for cyclometalation reactions or more general CH activation processes.
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  • 5
    ISSN: 0570-0833
    Keywords: Rhenium ; Catalysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Homogeneous catalysis as the major industrial outlet of organometallic basic research has been enjoying great benefit from organotransition metal species that promote bond forming between hydrocarbon fragments. Most of the commercially important processes that serve to produce large-volume organic feedstock chemicals such as linear α-olefins (Shell Higher Olefins Process), linear aldehydes (hydroformylation), acetaldehyde (Wacker-Hoechst), acetic acid (Monsanto), adiponitrile (DuPont hydrocyanation of butadiene) operate at low-valent metal centers. It is thus hardly surprising that by far the most part of organometallic research during the past few decades has been directed towards an understanding and the improvement of these catalytic reactions as well as towards the related stoichiometric chemistry. As a matter of consequence, our present knowledge on high-valent organotransition metal compound is comparatively shallow, nor do we know much about the chemical relationship and interconvertability of high and low oxidation states within a given class of compounds. In this article I want to point out some ostensibly challenging perspectives of future organometallic research by describing a novel class of high oxidation state organorhenium compounds as well as by speculating on possible generalizations for other transition metals.
    Additional Material: 18 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 21 (1982), S. 117-130 
    ISSN: 0570-0833
    Keywords: Fischer-Tropsch synthesis ; Catalysis ; Cluster compounds ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Fischer-Tropsch Synthesis counts among the industrial-scale processes having a versatile and broad product range, and has for decades offered the most attractive possibility for the use of coal as a source of heating oil and fuels. This conceivably simple reaction, the catalytic hydrogenation of carbon monoxide, generally leads to simple hydrocarbons as well (i.e. short chain olefins) that have been sought as chemical feedstocks since the oil crisis of the seventies, but fails to provide the large-scale, economic process required, due in large part to the minimal selectivity of traditional Fischer-Tropsch processes. In an effort to solve this problem current research in this sector is concerned not only with the optimization of old and the development of new catalytic systems, but also increasingly with the elucidation of numerous relevant reaction mechanisms. This article will discuss, from the viewpoint of an organometallic chemist, the significance of typical model reactions, both with regard to some fundamental aspects of synthesis gas chemistry, and in comparison with previous views concerning the mechanism of the Fischer-Tropsch Synthesis. The importance of various unique classes of complexes that have been studied in the context of Fischer-Tropsch chemistry is also evaluated with regard to their importance in the synthesis of hydrocarbons from carbon monoxide and hydrogen. It emerges that the primary steps of the reductive oligomerization of carbon monoxide are best described by the carbide/methylene mechanism, as originally proposed by Hans Fischer and Franz Tropsch.
    Additional Material: 6 Ill.
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  • 7
    ISSN: 0044-2313
    Keywords: Rhenium complexes ; carbonyl complexes ; nitrosyl complexes ; heptamethylindene ; crystal structures ; σ/η-bonding ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Syntheses of Metal Carbonyls. 23. Crystal Structure and Reactivity of Heptamethylindenyl Carbonyl Metal ComplexesReaction of heptamethylindene (C9(CH3)7, 1) with Re2(CO)10 yields [η5-C9(CH3)7]Re(CO)3 (2), which reacts with NO+BF4- to form the cationic complex [{η5-C9(CH3)7}Re(CO)2NO]+BF4- (3). Irradiation of 2 with UV light in the presence of triethyl phosphite leads to formation of [η5-C9(CH3)7]Re(CO)2[P(OC2H5)3] (4). Alkylation of (CH3)3SnCl with Ind*Li gives [η1-C9(CH3)7]Sn(CH3)3 (5). All compounds were characterized by spectroscopic methods. The molecular structures of 3 and 5 were determined by single crystal X-ray diffraction (3: P21/n (14), a = 1497.7(4) pm, b = 879.0(2) pm, c = 1609.0(4) pm and β = 110.99(2)°, R1 = 0.038, wR2 = 0.080; 5: P21/n (14), a = 726.1(1) pm, b = 2930.7(3) pm, c = 930.0(1) pm and β = 112.834(5)°, R1 = 0.044, Rw = 0.048). Complexes 2-4 exhibit a piano stool configuration with a η5-coordinated permethylindenyl ligand (Ind*). Compound 5 displays a η1 -coordination of the Ind* ligand. Temperature enhancement causes a hapticity change, as observed by NMR spectroscopy.
    Notes: Heptamethylinden (C9(CH3)7H, 1) reagiert mit Re2(CO)10 zu [η5-C9(CH3)7]Re(CO)3 (2), das durch Umsetzung mit NO+BF4- die kationische Verbindung[{η5-C9(CH3)7}Re (CO)2NO]+BF4- (3) und unter Bestrahlung mit UV-Licht in Anwesenheit von Triethylphosphit [η5-C9(CH3)7]Re(CO)2[P(OC2H5)3] (4) ergibt. Durch Alkylierung von (CH3)3SnCl wird [η1-C9(CH3)7]Sn(CH3)3 (5) erhalten. Alle Verbindungen wurden mit spektroskopischen Methoden vollständig charakterisiert. Von 3 und 5 wurden die Kristallstrukturen röntgenstrukturanalytisch bestimmt (3: P21/n (14), a = 1497.7(4) pm, b = 879.0(2) pm, c = 1609.0(4) pm und β = 110.99(2)°, R1 = 0.038, wR2 = 0.080; 5: P21/n (14), a = 726.1(1) pm, b = 2930.7(3) pm, c = 930.0(1) pm und β = 112.834(5)°, R1 = 0.044, Rw = 0.048). Während bei den Komplexen 2-4 der Heptamethylindenligand (Ind*) einen Halbsandwich-Komplex bildet (η5-Bindung zum Metall), so liegt in Derivat 5 erwartungsgemäß eine σ-Bindung zwischen einem C-Atom des Ind*-Liganden und dem Metallzentrum vor. Bei Temperaturerhöhung tritt eine Änderung der Haptizitätsverhältnisse ein (NMR-Evidenz).
    Additional Material: 2 Ill.
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