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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 1629-1639 
    ISSN: 0009-2940
    Keywords: Calculations, MNDO and HF ; GED data ; PE spectra ; Silicocene, decamethyl- ; Silicon(II) π-complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Decamethylsilicocen - die erste stabile Silicium(II)-Verbindung: Synthese, Struktur und BindungsverhältnisseDie Reaktion von Dichlorbis(pentamethylcyclopentadienyl)silan mit Naphthalin-Lithium, -Natrium oder -Kalium führt zu elementarem Silicium und zu Decamethylsilicocen (4). Bei der Reaktion von Dibrombis(pentamethylcyclopentadienyl)silan mit Anthracen-Kalium wird ausschließlich 4 gebildet. 4 ist ein thermisch stabiler, farbloser, luftempfindlicher π-Komplex. Seine NMR-Spektren sind typisch für Metallocene der Gruppe 14; das 29Si-NMR-Signal erscheint bei sehr hohen Feldstärken (δ = -398 ppm). CV- und MS-Daten von 4 belegen die Instabilität des (Me5C5)2Si⊖-Ions, das leicht ein Me5C5-Radikal verliert Nach Röntgenstrukturuntersuchungen liegen zwei geometrische Isomere, 4a und 4b, in der monoklinen Elementarzelle vor. Isomer 4a ist isotyp mit Decamethylferrocen, Isomer 4b besitzt die erwartete Struktur eines gewinkelten Metallocens. Nach Modellbetrachtungen liegt in 4b der größtmögliche Interplanar-Winkel vor. GED-Studien belegen für 4 eine gewinkelte Metallocen-Struktur in der Gasphase. Das He(I)-PE-Spektrum von 4 wird mit denjenigen der schwereren Homologen (Me5C5)2Ge (6), (Me5C5)2Sn (7) und (Me5C5)2Pb (8) verglichen. Für die Bande, die dem freien Elektronenpaar des Gruppe-14-Elements zugeordnet wird, ist beim Übergang von 8, 7 oder 6 zu 4 eine starke Verschiebung zu höherer Energie zu beobachten. Strukturmodelle der Stammverbindung (H5C5)2Si sind auf der Basis des MNDO-Konzepts und der HF-Theorie (STO-3G- und STO-3G*-Basissätze) berechnet worden. Die berechneten geometrischen Parameter und Orbital-Energien werden mit denjenigen aus dem GED-Experiment und dem PE-Spektrum verglichen. Die bathochrome Verschiebung in den Elektronenanregungsspektren beim Übergang von 4 zu 6-8 wird unter Zugrundelegung von MNDO-Rechnungen für die H-substituierten Metallocene erklärt.
    Notes: Reaction of dichlorobis(pentamethylcyclopentadienyl)silane with naphthalene-lithium, -sodium, or -potassium leads to elemental silicon and to decamethylsilicocene, (Me5C5)2Si (4). Compound 4 is formed as the only product in the reduction of dibromobis(pentamethylcyclopentadineyl)silane with anthracene-potassium. 4 is a thermally stable, colorless, air-sensitive π-complex. Its NMR spectra are typical for a group 14 metallocene; the 29Si-NMR signal appears at very high field strength (δ = -398 ppm). CV and MS data of 4 prove the instability of the (Me5C5)2Si⊖ ion, which easily looses a Me5C5 radical. X-ray crystallographic studies show the presence of two geometrical isomers, 4a and 4b, in the monoclinic unit cell. Isomer 4a is isotypical with decamethylferocene, isomer 4b possesses the expected bent-metallocene-type structure. Space-filling models indicate the interplane angle in 4b to be of the largest possible value. Due to GED studies, 4 has a bent-metallocene-type structure in the gas phase. The He(I) PE spectrum of 4 is compared with those of the heavier homologues (Me5C5)2Ge (6), (Me5C5)2Sn (7), and (Me5C5)2Pb (8). A strong shift to higher energy of the band assigned to the group 14 element lone pair is observed in going from 8, 7, or 6 to 4. Calculations have been carried out for structural models of the parent silicocene, (H5C5)2Si, on the basis of the MNDO procedure and of the HF theory (STO-3G and STO-3G* basis sets). The calculated geometrical parameters and orbital energies are compared with those derived from the GED experiment and from the PE spectrum. The bathochromic shift in the electronic absorption spectra going from 4 to 6-8 is explained on the basis of MNDO calculations for the parent metallocenes.
    Additional Material: 12 Ill.
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  • 2
    ISSN: 0009-2940
    Keywords: Cobalt, (η5-cyclopentadienyl)(1, 3-dibora-4, 5-benzopentafulvene)- ; Iron tricarbonyl complexes ; Triple decker, mixed-metal, slipped ; Calculations, ab initio, EH ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Complexation of 1, 3-Dihydro-1, 3, 10, 10-tetramethyl-1, 3-dibora-4, 5-benzopentafulvene with Fe(CO)3 and CpCo Fragments: Synthesis, Crystal and Electronic Structure of Tricarbonyl[(η5-cyclopentadienyl)cobalt][μ,η5:η4-(1, 3-dihydro-1, 3, 10, 10-tetramethyl-1, 3-dibora-4, 5-benzopentafulvene)]ironReaction of the 1, 3-dibora-4, 5-benzopentafulvene 1 with the isolobal organometallic fragments Co(C5H5) and Fe(CO)3 leads to the slipped triple-decker complex 5. It is also formed when 2 is stacked with the Co(C5H5) fragment. The X-ray structure analysis of 5 reveals that the Co(C5H5) fragment is coordinated to the 1, 3-diborole ring, and the Fe(CO)3 group interacts with the Y-shaped B2C=C unit. An MO calculation indicates that the formation of 5 occurs by distortion of 2 (η5- → η4-bonding) and complexation of the Co(C5H5) group. 5 is 16 kcal/mol more stable than its structural isomer 6.
    Additional Material: 1 Tab.
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  • 3
    ISSN: 0009-2940
    Keywords: 1,3-Diborapentafulvene ; Iron tricarbonyl complexes ; Slipped triple-decker ; Calculations, ab initio, EH ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Complexation of 1,3-Dihydro-1,3-diborapentafulvene Derivatives with Fe(CO)3 Fragments: Syntheses, Crystal and Electronic Structure of μ-(η4: η5-1,3-Dihydro-1,3-diborapentafulvene)-bis(tricarbonyliron) ComplexesReactions of the 1,3-diborapentafulvene derivatives 1a-c with (CO)3Fe(C8H14)2 lead to the violet dinuclear complexes 3a-c, which possess a slipped triple-decker structure. The X-ray structure analyses of 3b,c reveal that one Fe(CO)3 group is pentahapto-coordinated to the 1,3-diborole frame of C2B2C=C, whereas the other interacts with the Y-shaped B2C=C unit. The latter resembles the interaction of Fe(CO)3 with trimethylenemethane. An MO calculation indicates that the formation of 3 occurs by distortion of 1 · Fe(CO)3; the slippage of Fe(CO)3 from η5 to η4 bonding is followed by η5 coordination of the second Fe(CO)3 group.
    Additional Material: 4 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2363-2365 
    ISSN: 0009-2940
    Keywords: Dimethoxysulfane ; Dimethoxydisulfane ; Photoelectron spectra ; Calculations, MO ; Ligand properties ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The He(I) photoelectron spectra of dimethoxysulfane (1) and dimethoxydisulfane (2) have been recorded. The lowest energy ionizations in the PE spectrum of 1 can be explained by assuming C2 symmetry. They can be described as arising from linear combinations between the 3p lone-pair at sulfur and 2p lone-pairs at the oxygen atoms. A comparison between the calculated MO sequence of 2 for different conformations and the first PE bands shows a good agreement with an OSSO torsional angle near 90°. The highest occupied MOs of 2 can be described as linear combinations between the 3p MOs of the S2 unit and linear combinations between the 2p AOs of the oxygen atoms.
    Additional Material: 4 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1557-1561 
    ISSN: 0009-2940
    Keywords: MO calculations, EH ; Iron, tricarbonyl(η6-1,4-dihydro-1,4-diboranaphthalene)- ; Bis(tricarbonyliron) ; Dicarbonyliron-tricarbonyliron ; Bis(cyclopentadienyliron) complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure and bonding of four iron complexes involving the 1,4-dihydro-1,4-diboranaphthalene ligand C8B2H8 (1), namely of the complexes (CO)3Fe(η6-C8B2H8) (2), (μ, η4,η6-C8B2H8)[Fe(CO)3]2 (3), (CO)3Fe(μ,η4,η6-C8B2H8)Fe(CO)2 (4), and of the triple-decker (μ,η6-C8B2H8)[Fe(η5-C5H5)]2 (5), have been investigated by means of the perturbational molecular orbital theory on the basis of the Extended Hückel calculations. Compounds 2 and 3 are 18-VE complexes, whereas 5 is a 30-VE species. The structure of 4 can be best described in terms of a 16-VE complex “Fe(CO)3 heterocycle” and a 18-VE “Fe(CO)2 carbocycle” unit with its iron centers being not directly bond.
    Additional Material: 6 Ill.
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