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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 70 (1986), S. 407-419 
    ISSN: 1432-2234
    Keywords: Correlation energy ; Density functional ; First-row atoms ; First-row hydrides ; First-row dimers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Four density functionals — including that recently introduced by Perdew ((1986) Phys Rev B33: 8822)—are tested for first-row atoms, hydrides and dimers. Calculated contributions of the correlation energy to the ionization potentials and electron affinities of atoms and to the dissociation energies of molecules are compared with “empirical” values which were reevaluated for this purpose. An improvement over Hartree-Fock is found in all cases if the self-interaction or the gradient correction are included in the density functional, although there is a rather large variation in the accuracy of the predictions.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0044-2313
    Keywords: Bis[triglymesodium(1+)][Tetrakis(borane)sulfate(2-)], [Na · Triglyme]2[S(BH3)4] ; preparation ; crystal structure ; SCF calculations ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: [Na · Triglyme]2[S(BH3)4]: a Salt of the New Anion Tetrakis(borane)sulfate(2- ). Crystal Structure and Theoretical Investigation of the StructureNa[H3B-m̈2-S(B2H5)] 1 is produced by the reaction between NaSH and THF · BH3, under dehydrogenation. 1 is also formed as the first 11B-NMR-spectroscopically detectable reaction product by the reaction between anhydrous Na2S and THF · BH3. Adducts of BH3 with the S2- ion are not detectable in THF. The anion [S(BH3)4]2- can however be obtained, by the addition of NaBH4 to 1 in diglyme or triglyme respectively: [Na  -  Triglyme]2[S(BH3)4] 2. 2 crystallizes in the monoclinic space group P21/n (Nr. 14). Structural data of 1 and 2 have been calculated by SCF methods. The anion of 2 may be viewed either as an adduct of B2H6 with S2-, or as a bridge substituted thia derivative of B2H7-; furthermore the anion of 2 is isoelectronic and isostructural with the SO42- ion.
    Notes: Bei der Reaktion zwischen NaSH und THF · BH3 entsteht unter H2-Abspaltung Na[H3B-m̈2-S(B2H5)] 1. 1 entsteht auch als erstes 11B-NMR-spektroskopisch nachweisbares Reaktionsprodukt bei der Reaktion zwischen wasserfreiem Na2S und THF · BH3. Addukte von BH3 an das S2--Ion lassen sich in THF als Lösungsmittel nicht nachweisen. Das neue Anion [S(BH3)4]2- kann jedoch durch Addition von NaBH4 an 1 in Diglyme bzw. Triglyme erhalten werden: [Na · L]2[S(BH3)4] 2. 2 kristallisiert monoklin in der Raumgruppe P21/n (Nr. 14). Aus SCF-Rechnungen erhielten wir die Strukturparameter für 1 und 2. Das Anion von 2 kann sowohl als Addukt von B2H6 an S2- als auch als brückensubstituiertes Thia-Derivat des B2H7--Ions aufgefaßt werden; ferner ist es isoelektronisch und isostrukturell mit dem SO42-- Ion.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0044-2313
    Keywords: [Disodium(2 +)][1,2-Diselena-diboranate(2 -)] ; [Tetraphenylphosphonium(1 +)][μ2-Selena-(diboranyl)boranate(1 -)] ; preparation ; SCF calculations ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Vibrational Spectroscopic Investigation of [H3B—Se—Se—BH3]2- and [H3B-μ2-Se(B2H5)]- Crystal Structure and Theoretical Investigation of the Molecular Structure of [H3B-μ2-Se(B2H5)]-M2[H3B—Se—Se—BH3] 1 is produced by the reaction between elemental selenium and MBH4 (1 : 1) in triglyme (diglyme), under dehydrogenation. 1 reacts with an excess of B2H6 to give M[H3B-μ2-Se(B2H5)] 2 which is also formed in the reaction of THF · BH3 with 1. These reactions proceed under cleavage of the Se—Se bond and hydrogen evolution. [(C6H5)4]Br reacts with Na · 2 to form [(C6H5)4P] · 2 which crystallizes in the tetragonal space group I4 (Nr. 82). An X-ray structure determination failed because of disordering of the cation and anion. 11B, 77Se NMR shifts and 1J(11B1H) coupling constants as well as IR- and Raman spectroscopic investigations convey further structural information. Structural data of 2 have been calculated by SCF methods. The anion of 2 may be viewed either as an adduct of Se with B3H8-, or as a bridge substituted selena derivative of B2H6.
    Notes: Bei der Reaktion zwischen elementarem Selen und MBH4 (1 : 1) (M = Na, Li) in Triglyme (Diglyme) entsteht unter Wasserstoffabspaltung M2[H3B—Se—Se—BH3] 1. Bei der Behandlung von 1 mit überschüssigem B2H6 oder THF · BH3 wird die Se—Se-Bindung gespalten und es entsteht unter erneuter Wasserstoffabspaltung M[H3B-μ2-Se(B2H5)] 2. Aus Na · 2 und [(C6H5)4P]Br entsteht [(C6H5)4P] · 2, welches tetragonal in der Raumgruppe I4 (Nr. 82) kristallisiert. Kation und Anion sind im Kristall fehlgeordnet. Strukturinformationen konnten aus den 11B-, 77Se- und 1J(11B1H)-Daten einerseits und den IR- und Raman-spektroskopischen Untersuchungen andererseits erhalten werden. Aus SCF-Rechnungen erhielten wir die Strukturparameter für das Anion 2. 2 kann sowohl als Addukt von Se an B3H8- als auch als brückensubstituiertes Selena-Derivat des B2H6 aufgefaßt werden.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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