scispace - formally typeset
Search or ask a question

Showing papers on "Inorganic compound published in 1986"



Journal ArticleDOI
TL;DR: In this article, the shape of coordination polyhedra of di-n-butyltin(IV) compounds and their complexes in coordinating and non-coordinating solvents was described from analysis of their δ(119Sn) and 1J(119sn-13C) parameters.

494 citations
















Journal ArticleDOI
TL;DR: In this article, the relationship between the 31P n.m.r. chemical shifts of crystalline inorganic inorganic phosphates and the bond strengths at the phosphate oxygen atoms was investigated.
Abstract: Correlations have been observed between the 31P n.m.r. chemical shifts of crystalline inorganic phosphates and the bond strengths at the phosphate oxygen atoms; these provide a basis for structural studies and for peak assignment in phosphates that give more than one resonance.







Journal ArticleDOI
TL;DR: Mossbauer et al. as discussed by the authors determined the structures of cristallines du triiodure de diiodobiferrocenium and de l'octaiodure de dichlorobiferricrocenium.
Abstract: Determination des structures cristallines du triiodure de diiodobiferrocenium et de l'octaiodure de dichlorobiferrocenium. Spectres Mossbauer, RPE et IR

Journal ArticleDOI
TL;DR: The self consistent field multiple scattering Xa model has been used to calculate the electronic structure and the magnetic coupling constant, J, of planar and pseudotetrahedral complexes with the aim of exploiting the actual possibilities of the model to describe the spectral (electronic and EPR) and magnetic properties of transition-metal polynuclear complexes.
Abstract: The self consistent field multiple scattering Xa model has been used to calculate the electronic structure and the magnetic coupling constant, J , of planar and pseudotetrahedral [ C U ~ C I ~ ] ~ complexes with the aim of exploiting the actual possibilities of the model to describe the spectral (electronic and EPR) and magnetic properties of transition-metal polynuclear complexes. The observed variation of J with the degree of tetrahedral distortion has been quantitatively reproduced. The 19 000-cm-' feature characteristic of the electronic spectra of hexachlorodicuprate(l1) complexes is computed in the present calculations as a chlorine-to-metal charge transfer. The exchange interactions between transition-metal ions in orbitally nondegenerate states have been extensively studied in oligonuclear and polynuclear c~mplexes . l -~ These interactions generate manifolds of closely spaced levels which give the molecule unusual magnetic properties and have attracted the interest of both theoreticians and experimentalists. Two types of interactions can occur. To the first type belong the magnetic interactions which involve the ground states of the ions in the cluster. These are usually the strongest ones and isotropic in space. To the second type belong the interactions involving the excited states of the ions. These are usually less than I cm-I and highly anisotropic. A number of experimental techniques, ranging from the measurement of the temperature dependence of magnetic susceptibility to optical spectroscopy and magnetic resonance techniques, have been employed to measure also very weak interactions involving both the ground and the excited electronic Many studies have been devoted to the correlation of the isotopic exchange interaction with the electronic structure and geometry of the c o m p l e x e ~ . ~ The effect of this interaction on the energy levels of the cluster is generally represented by using a spin Hamiltonian approach through the operator where the sum runs all the neighboring paramagnetic metal atoms with total spin S,, and Jab is the exchange coupling constant between atoms a and b, which is evaluated experimentally. The Jab values are commonly related to the electronic structure of the polynuclear molecule by using semiempirical methods based on the Anderson theory of superexchangelo*" or using orbital models which relate the Jab values to overlap and energy differences between molecular orbitals evaluated within Ligand Field1* or extended Huckel formali~ms.l~'~ The use of these models allowed the rationahation of the magnetic properties of series of structurally related complexes, but they did not give any quantitative estimate of the S s. The actual calculation of the J a b values with more rigorous M O methods is hampered by the necessity of computing energy differences of the order of 10'-102 cm-l which are largely affected by electron correlation. In order to overcome this problem, whose solution requires extensive configuration interactions, a perturbation approach has recently been suggested to calculate Jab with an a b initio approach. Calculations have been performed on copper(l1) acetate,I6 oxalate," and di-pchloro bridged1* dimers. The agreement between the experimental and the computed J values was generally satisfactory. By using a b initio models, however, it is not a simple task to compute other physical observables such as electronic transitions and EPR parameters, which *Address correspondence to this author at the Institute per lo Studio della Stereochimica ed Energetica dei Composti di Coordinazione del C.N.R. 0002-7863/86/1508-5763$0l .SO10 constitute a severe test of the applicability of the model to the description of the electronic structure of transition metal clusters. A more approximate method than a b initio but still retaining enough flexibility in the radial wave functions is needed in order to make the problem computationally tractable. In recent years density functional methods have been shown to give an accurate description of the properties of open-shell transition-metal c o m p l e ~ e s . ' ~ In particular the Slater-Johnson Xa-SW has been applied with some success to calculate the electronic structure of several transition-metal complexes.22-2x ( I ) Martin, R. L. In New Pathways in Inorganic Chemistry; Ebsworth, E. A. V., Maddock, A. G.; Sharpe, A. G., Eds.; Cambridge University Press: 1968. ( 2 ) Hodgson, D. J . Progr. Inorg. Chem. 1975, 19, 173. (3) Ginsberg, A. P. Inorg. Chim. Acta, Re[. 1971, 5, 45. (4) Kokoszka, G. F.; Gordon, G. I n Transition Meral Chemistry; Carlin, R. L., Ed.; Marcel Dekker: New York, 1969; Vol. 5, p 181. ( 5 ) Carlin, R. L.: Duyneveldt, A. J . Magnetic Properties o/ Transition Metal Compounds; Springer-Verlag: New York, 1977. ( 6 ) O'Connor, C. J . Progr. Inorg. Chem. 1982, 29, 203. (7) Day, P. Acc. Chem. Res. 1979, 12, 236. ( 8 ) Gatteschi, D. In The Coordination Chemistry oJ Metalloenzynies; Bertioi, I., Drago, R . S., Luchinat, C., Eds.: D. Reidel: Dordrecht, 1983: p 215. (9) Magneto Structural Correlations in Exchange Coupled Sysfems; Willett, R. D., Gatteschi, D., Kahn, O., Eds.; D. Reidel: Dordrecht, 1985. ( I O ) Anderson, P. W. Phys. Rec. 1959, 115, 2. ( 1 1 ) Anderson, P. W. In Magnetism; Rado, G. T.. Suhl, E. H., Eds.; (12) Bencini, A.; Gatteschi, D. Inorg. Chim. Acta 1978, 31, 1 I . (13) Hay, P. J . ; Thibeault, J . C.; Hoffman, R. J . Ant. Chem. Soc. 1975, (14) Kahn, 0.; Briat, B. J . Chem. Soc., Faraday Trans. 2 1976, 72, 268. (15) Kahn, 0.; Briat, B. J . Chem. Soc., Faraday Trans. 2 1976, 72, 1441. (16) De Loth, P.; Cassoux, P.; Daudey, J. P.; Malrieu, J . P. J . A m . Chem (17) Chariot, M. F.; Verdaguer, M.; Journaux, Y . ; De Loth, P.; Daudey. (18) Bencini, A.; Daudey, J . P.; Gatteschi. D., to be published. (19) Computational Methods f o r Large Molecules and Localized States in Solids; Herman, F., McLean, A. D., and Nesbet, R. K., Eds.; Plenum: New York, 1979. Academic Press: 1963.


Journal ArticleDOI
TL;DR: In this paper, the authors examined the electrical, magnetic and structural properties of Ta2NiS5/Ta2NiSe5 and showed that the properties are more consistent with the materials being small band gap semiconductors.
Abstract: The compounds Ta2NiS5 and Ta2NiSe5 have a novel layered structure: within the layers are rows of tantalum atoms separated by rows of nickel atoms. The lower dimensional structure of these compounds as well as the expected d1 non-bonding electron configuration of the tantalum atom leads to the expectation that classical charge density wave behavior would be observed in their properties. An examination of the electrical, magnetic and structural properties shows that this is not the case; rather, the properties are more consistent with the materials being small band gap semiconductors. Further, both compounds show structural phase transitions: in Ta2NiS5 a first-order transition occurs at 28 K and in Ta2NiSe5 a second-order transition occurs at 328 K. The latter transition is shown by electron microscopy to be martensitic-like.



Journal ArticleDOI
TL;DR: The second-harmonic generation efficiencies of over 60 transition-metal-organic compounds in powder form were measured, using 1.06 µm light from a Nd:YAG laser.
Abstract: The second-harmonic generation efficiencies of over 60 transition-metal-organic compounds in powder form were measured, using 1.06 ..mu..m light from a Nd:YAG laser. Most of the studied compounds were either group VI metal carbonyl arene, pyridyl, or chiral phosphine complexes. Four the complexes doubled the laser fundamental as well as or better than ammonium dihydrogen phosphate (ADP). The study shows that the same molecular features (e.g., conjugation and low-lying spectroscopic charge transfer) that contribute to second-order optical nonlinearity in organic compounds also enhance second-order effects in transition-metal-organic compounds.