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  • 1
    ISSN: 1572-8862
    Keywords: Quasi-aromaticity ; trinuclear iron cluster ; localized MO ; heterometal cluster
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The localized molecular orbitals and their energy levels for the clusters [Fe3S4(SH)3]2−, [(HS)3Fe3S4·Ni(PH3)]2−, [Mo3S4(OH2)9]4+, and [Mo3S4·Ni]4+ have been calculated by mean of the Edmiston-Ruedenberg energy localization technique under the CNDO/2 approximation in order to reveal the resemblance between [Fe3S4]+ and [Mo3S4]4+ in the geometrical configurations and the addition reactivities with heterometal atoms. It is shown that in these two cluster species with core {M 3(μ3-S)(α-S)3} of similar structure (M = Mo, Fe) there exist three synergically connected three-centered two-electron (M-S-M) π-bonds around the puckered six-membered {M3S3} rings on account of delocalization of a lone electron pair on each bridging S atom; these (M-S-M) π-bonds are thus capable of forming cubane-like heterometal clusters with “intruder” metal atoms through the (π → M) bonding. It is therefore seen that unlike the [Mo3S4]4+ with appreciable bonding between the Mo atoms, the extra d-electrons on the metal atoms in the [Fe3S4]+ cluster are localized on the Fe atoms, exhibiting an electronic structure significantly different from that of the [Mo3S4]4+ cluster.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-8862
    Keywords: Heterometal cluster ; Mo-Cu cluster ; localized MO ; chemical bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The localized molecular orbitals (LMOs) and Mulliken bond orders for the cluster anions of [Et4N]2[Mo2S4(edt)2] (1), [(CH3CH2)4N][Mo2CuS4(PPh3)(edt)2] (2) and the cluster molecule [Mo2Cu2S4(PPh3)2(edt)2] (3) have been calculated by means of the Edmiston-Ruedenberg energy localization technique under the CNDO/2 approximation. The results of the LMOs calculations show that there are two pairs of π(S1 → Mo) bonds each pair of the Mo atoms and the terminal S1 atoms in the anion of (1). In the addition reactions of the cluster compound (1) with one or two Cu atoms these π(S1 → Mo) bonds are sequentially opened and form correspondently the cluster compounds (2) and (3) with the three-centered or four-centered bonds among the copper, sulfur, and molybdenum atoms, accounting for the stronger bonding of the Cu atom to the Mo-S cluster compounds such as (1). This also gives the explanation of chemical bonding for the [2+1] and [2+2x1] synthetic reaction schemes of the compounds (2) and (3). The structural features for the cluster compounds studies are briefly discussed as well.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1572-8862
    Keywords: Multicentered bonding ; quasi-aromaticity ; localized MO ; cluster ; bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract On the basis of the localized molecular orbital (LMO) theory, the bonding schemes for the following types of cluster compounds are briefly reviewed in this paper; the linear [Et4N][Cl2FeS2MoS2Cu(PPh3)2] cluster, triangular trinuclear [M 3(μ3−X)(μ−Y 3]4+ (M = Mo, W;X = O, S;Y = O, S, Se) clusters, triangulated polyhedral clusters: closo-boranes B n H n 2−, octahedral [Co6(CO)14]4−, [Ni2Co4(CO)14]2− and [Co6(μ3 −X 8 ·L 6 n+ (X = S, Se;L = PPh3, PEt3, CO;n = 0,1) as well as quasi-aromatic cluster ligands in cubane-type [Mo3S4 ·ML n (4 +q) + (M = Mo, W, Fe, Ni, Cu, Sn, Sb;L = Ligand and sandwich-type [Mo3S4 ·M · S4Mo3]8+ (M = Mo, Sn, Hg). We put emphasis upon the characteristics of multicentered bonding in these cluster molecules, and, especially, point out existence of a novel species of quasi-aromatic cluster compounds.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In order to explore the dynamic problem of the electronic structure in the ground state for the Creutz–Taube ion, the calculations on the electronic potential surfaces along the totally symmetric vibrational difference coordinate of the Ru–N stretch and the net charge distribution on the Ru atoms are carried out by using the density functional theory in the two schemes with or without the Ru–N(pyz) vibration. It is shown that the vibration associated with the totally symmetric vibrational difference coordinate Q− can be regarded as a harmonic oscillation with 123.16 eV Å−2 of the force constant, and 430 cm−1 of the fundamental frequency is obtained on the basis of the five-body vibrator model. From the electronic structure calculated in the ground state it is concluded that the asymmetric net distribution on the Ru atoms in the Creutz–Taube ion occurs in the vibration associated with the totally symmetric vibrational difference coordinate, and the charge transfer between the Ru atoms and the ligands is responsible for the asymmetric charge distribution. The total symmetric vibrations of Ru–N for the related monomer [(NH3)5Ru(pyz)]2+/3+ are further examined. It is found that the reduction of Ru(III) to Ru(II) corresponds to 0.05 Å of the difference in Ru–N distance between the two Ru-subunits under the asymmetric distortion and to 0.012 eV of the potential energy over the zero point energy, which is comparable with kT. The Born–Oppenheimer approximation and the neglected coupling effect between the electronic and nuclear motion in the present paper are briefly discussed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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