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《Journal of Coordination Chemistry》2012,65(3):490-500
A systematic search of the Cambridge structural database was undertaken to quantify the trans influence in square planar and octahedral transition metal compounds. For square planar geometry, d8 metal centers were studied, while octahedral searches focused on low-spin d6 complexes. Two probe ligands (PL) were used to measure the effect of the trans ligand (TL), chloride, and triphenylphosphine (PPh3). For the TLs O=CX2, NR3, pyridine, and Cl? (X?=?any non-metal, R?=?H or hydrocarbon), the effects on the metal–probe ligand (M–PL) distance were statistically equal and were taken as essentially no trans influence. The other ligands studied showed significant decrease in the mean M–PL bond order, relative to the above ligands: SR2?=?0.941; S=CX2?=?0.887; PPh3?=?0.825; phenyl?=?0.743; CR3?=?0.719; hydride?=?0.685. Some variation in the trans influence is observed, based on the geometry of the metal center and the PL. In general, electron-donating, σ-bonding ligands lead to a larger trans influence, but π-bonding effects can also be important, particularly when the probe ligand also has π-bonding properties. 相似文献
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Exact spin-pairing energies are calculated by direct diagonalization of the relevant ligand field plus interelectronic repulsion matrices for the configurations d
4, d
5, d
6, and d
7 of octahedral transition metal ions. The results are presented in terms of /B as function of = C/B for the range of values =3.0 to 8.0. Comparison with the quantity resulting from a simplified approach in which configuration interaction is neglected or considered on an approximate basis only reveals significant differences. Useful estimates of spin-pairing energies are provided, in addition, on the basis of empirical magnetic and electronic spectral data.
Zusammenfassung Exakte Spinpaarungsenergien für die Konfigurationen d 4, d 5, d 6 und d 7 oktaedrischer Übergangsmetallionen werden durch direkte Diagonalisierung der entsprechenden Matrizen des Ligandenfeldes sowie der Elektronenwechselwirkung berechnet. Die Ergebnisse für /B werden in Abhängigkeit von = C/B für den Wertebereich =3.0 bis 8.0 angegeben. Ein Vergleich mit der Größe , die bei einer vereinfachten Behandlung unter Vernachlässigung oder näherungsweiser Berücksichtigung der Konfigurationswechselwirkung erhalten wird, zeigt auffallende Unterschiede. Nützliche Abschätzungen der Spinpaarungsenergie werden außerdem unter Benutzung empirischer magnetischer und elektronenspektroskopischer Daten erhalten.
Résumé Les énergies exactes de couplage de spin sont calculées par diagonalisation directe du champ de ligand correspondant en plus des matrices de répulsion électronique pour les configurations d 4, d 5, d 6 et d 7 des ions octaédriques des métaux de transition. Les résultats sont présentés en termes de /B en fonction de = C/B dan l'intervalle =3,0 à 8,0. On trouve des différences significatives par comparaison de avec les valeurs résultant d'une approche simplifiée sans interaction de configuration ou avec interaction de configuration approchée. De plus, des estimations des énergies de couplage de spin sont obtenues à partir de données empiriques magnétiques et spectrales.相似文献
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Russian Chemical Bulletin - Quantum chemical calculations of the molecular and electronic structure of the complexes [(L)2M13+(L)M22+(L)2]5? (M13+ is the Mo ion in the oxidation state +3;... 相似文献
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The apparent stability constants for porphyrin and metalloporphyrin complexes with an electron acceptor have been determined in mixed solvents. The variation of the apparent stability with solvent composition is evaluated in terms of solvation of the complex and reactant species and in terms of the exclusion of the solvent from the solvation sheath of the reactants, according to the equilibrium AS
a
+DS
b
=CS
x
+yS. 相似文献
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Lamonova KV Zhitlukhina ES Babkin RY Orel SM Ovchinnikov SG Pashkevich YG 《The journal of physical chemistry. A》2011,115(46):13596-13604
Electronic spectra of 3d(n) transition ions in an octahedral ligand surrounding have been studied using the modified crystal field approach (MCFA), which includes a relativistic spin-orbital interaction. A new variable parameter, the effective nuclear charge Z(eff) of a metal ion that allows accounting implicitly the covalence degree of a metal-ligand bond, has been introduced. Energy diagrams similar to the Tanabe-Sugano ones have been calculated. To study the spin state evolution of the metal ion in an arbitrary distorted octahedral complex, a spin state diagram approach has been proposed. The intermediate-spin (IS) state problem for 3d(4), 3d(5), and 3d(6) metal ions has been considered and conditions for the IS state realization have been formulated. The regions of the mixed high-, intermediate-, and low-spin states have been found. The possibility of coexistence of the different spin states of 3d ions in the octahedral complexes has been considered using crystallography data for the YBaCo(2)O(5.5) layered cobaltite. 相似文献
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Proton NMR spectra of the dithioformate ligands in an extensive range of new platinum metal dithioformato complexes permit unambiguous assignment of stereochemistry. 相似文献
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A precursor of non-aqueous porphyrins such as tetraphenyl porphyrin was synthesized and metallated with Ag, Mn and Sn to get respective metalloporphyrins. Further, they were characterized by UV–Vis spectroscopy, IR spectroscopy and proton NMR. Thermal studies of the above compounds were carried out using thermal analyser in synthetic air from room temperature to 800 °C. This analysis revealed that these compounds have thermal stabilities up to 400 °C and therefore can be successfully employed as heterogeneous catalysts as well as in semiconductor devices. In tin metalloporphyrin two Cl ligands, one above and other below the porphinato plane is comparatively stabilizing the structure to more symmetrical one which is responsible for more thermal stability. Further, residues of these compounds obtained after heating up to 800 °C, showed the presence of metal oxides and coal, respectively. 相似文献
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The distribution of di-, tri-, and tetracoordination among the d(10) ions of the group 11 metals is theoretically analyzed by means of density functional calculations on more than 150 model complexes of general formula [MX(m)L(n)](1-m) (where M = Cu, Ag, or Au; L = NH(3) or PH(3); X = Cl, Br, or I; m + n = 2-4). The energy of a ligand association reaction has been found to be practically determined by two contributions: the interaction energy and the energy of deformation of the metal coordination sphere. The larger deformation energy of gold complexes compared to copper and silver ones explains the predominance of dicoordination among Au(I) complexes, in comparison with Cu(I) and Ag(I), for which dicoordination is far less common than tri- and tetracoordination. Other experimental trends can be explained by looking at the fine details of these two energetic components. 相似文献
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Russian Journal of General Chemistry - 相似文献
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Gulino FG Lauceri R Frish L Evan-Salem T Cohen Y De Zorzi R Geremia S Di Costanzo L Randaccio L Sciotto D Purrello R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(10):2722-2729
The interactions of the tetracationic meso-tetrakis(N-methyl-4-pyridyl)porphyrin (H(2)TMPyP) and its metallo derivatives (MTMPyP) (where M=copper(II), zinc(II), and gold(III) with the octa-anionic form (at neutral pH) of 5,11,17,23-tetrasulfonato-25,26,27,28-tetrakis(hydroxycarbonylmethoxy)calix[4]arene (C(4)TsTc) lead to a series of complex species whose stoichiometry and porphyrin sequence can be easily tuned. Crystallographic, spectroscopic, and diffusion NMR studies converge towards a common picture in which a central 1:4 porphyrin/calixarene unit serves as a template for the formation of more complex species. These species arise by successive, stepwise addition of single porphyrin molecules above and below the plane of the 1:4 central core to ultimately give a 7:4 complex. Noticeably, the stoichiometry of the various complex species corresponds to the actual concentration ratio of porphyrins and calixarenes in solution allowing the stoichiometry of these species to be easily tuned. This behavior and the remarkable stability of these species allow homo-porphyrin and hetero-(metallo)porphyrin species to be formed with control of not only the stoichiometry but also the sequence of the porphyrin array. The flexibility and ease of this approach permit, in principle, the design and synthesis of porphyrin arrays for predetermined purposes. For example, we have shown that it is very easy to design and obtain mixed porphyrin species in which a foreseen photoinduced electron-transfer is indeed observed. 相似文献
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Using the1H and13C NMR method, we have observed delocalization of spin density from the paramagnetic metalloporphyrins to aromatic nitro compounds in chloroform solutions. We have shown that spin transfer occurs directly from the metal atoms. The effectiveness of spin transfer varies in the order Co2+ > Mn3+ > Fe3+ > Cu2+, correlating with the accessibility of the dz2 orbital of the metal containing the unpaired electrons.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1009–1015, May, 1990.We thank A. B. Solov'eva and G. V. Ponomarev for providing the metalloporphyrins. 相似文献