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1.
The metallacarborane [3,3′‐Co(1,2‐closo‐C2B9H11)2]? has been synthesized. This species allows the formation of redox couples in which both partners are negatively charged. The E1/2 potential can be tuned by adjusting the nature and number of substituents on B and C. The octaiodinated species [3,3′‐Co(1,2‐closo‐C2B9H7I4)2]? is the most favorable, as it is isolatable and stable in air. A DFT study on stability and redox potentials of complexes has been performed.  相似文献   
2.
The application of theoretical methods based on the density functional theory with hybrid functionals provides good estimates of the exchange coupling constants for polynuclear transition metal complexes. The accuracy is similar to that previously obtained for dinuclear compounds. We present test calculations on simple model systems based on H. He and CH(2). He units to compare with Hartree-Fock and multiconfigurational results. Calculations for complete, nonmodeled polynuclear transition metal complexes yield coupling constants in very good agreement with available experimental data.  相似文献   
3.
During attempts to synthesize rare‐earth nitride tellurides black and bead‐shaped single crystals of the title compound sodium praseodymium(III) ditelluride (NaPrTe2) were obtained as a by‐product by reacting a mixture of praseodymium, sodium azide (NaN3) and tellurium at 900 °C for seven days in evacuated torch‐sealed silica vessels. NaPrTe2 crystallizes cubic (space group: Fd3¯m, Z = 16; a = 1285.51(9) pm, Vm = 79.96(1) cm3/mol, R1 = 0.028 for 146 unique reflections) and exhibits the Na+ and Pr3+ cations in slightly distorted octahedra of six telluride anions (d(Na—Te) = 325 pm, d(Pr—Te) = 317 pm) each. The main characteristics of this new structure type for alkali‐metal rare‐earth(III) dichalcogenides can be derived from the rock‐salt type structure (NaCl, cubic closest‐packed Te2— arrangement, all octahedral voids occupied with Na+ and Pr3+) with alternating layers consisting of Na+ and Pr3+ cations in a ratio of 3:1 and 1:3, respectively, piled along the [111] direction.  相似文献   
4.
5.
About Lanthanide Oxotantalates with the Formula MTaO4 (M = La – Nd, Sm – Lu) Besides being a by‐product of solid state syntheses in tantalum ampoules the lanthanide(III) oxotantalates of the formula MTaO4 can be easily prepared by sintering lanthanide sesquioxide M2O3 and tantalum(V) oxide Ta2O5 with sodium chloride as flux. Under these conditions two structure types emerge depending upon the M3+ cationic radius. For M = La – Pr the MTaO4‐type tantalates crystallize in the space group P21/c with lattice constants of a = 762(±1), b = 553(±4), c = 777(±4) pm, β = 101(±1)° and four formula units per unit cell. With M = Nd, Sm – Lu, the monoclinic cell dimensions (space group P2/c) shrink to the lattice constants like a = 516(±9), b = 551(±9), c = 534(±9) pm, β = 96.5(±0.3)° and there are only two formula units present. Both structures show a coordination sphere of eight oxygen atoms for the lanthanide trications shaped as distorted square antiprism for the structure with the larger lanthanides (in the following referred to as A‐type) and as trigonal dodecahedron for the structure with the smaller ones (called as B‐type in the following). The coordination environment about the Ta5+ cations can be described as a slightly distorted octahedron (CN = 6) for the A‐type structure of MTaO4 and a heavily distorted one (CN = 6) for the B‐type. The difference between the two types results from the interconnection of these [TaO6]7? octahedra. Whereas they are connected via four vertices to form corrugated layers according to parallel the bc‐plane in the A‐type, the octahedra of the B‐type MTaO4 structure share edges to built up zig‐zag chains along the c axis.  相似文献   
6.
A New Samarium Nitride Sulfide: Sm4N2S3 The oxidation of samarium with sulfur in the presence of SmCl3 and NaN3 as nitrogen source (molar ratio: 12:9:4:2, evacuated silica vessel, some NaCl as flux, 850°C, 7 d) yields Sm4N2S3 as lath-shaped, dark red single crystals. The by-products (NaCl and NaSm2Cl6) are rinsed with water from the crude product. The crystal structure of Sm4N2S3 (monoclinic, C2/m (no. 12), Z = 2, a = 1 318.04(12), b = 391.57(2), c = 1 031.76(9) pm, β = 130.874(6)°, R = 0.036, Rw = 0.031) contains two crystallographically different Sm3+, both in sixfold coordination of the anions. Besides distorted octahedra [(Sm1)N3S3] and [(Sm2)NS5], tetrahedra [(N3?)(Sm)] connected via two cis-oriented edges to form chains [N(Sm1)3/3(Sm2)1/1]3+ build up the Mayn structural feature. These are arranged in the fashion of a closest packing of rods and held together by two crystallographically different S2? anions which take care for charge neutrality and three-dimensional interconnection.  相似文献   
7.
M4X3[Si2O7]-Type Lanthanide Chalcogenide Disilicates (M ? Ce? Er; X ? S, Se) Attempts to produce single crystals of MSe2 (or MSe2?X) by vapour phase transport with iodine or the oxidation of MCl2 (or MClH) with sulfur in the presence of NaCl in sealed evacuated quartz containers often yielded well-grown single crystals with the composition M4X3[Si2O7] (M ? pr, Sm, Gd, X ? Se, and M ? Nd, Er, X ? S) as by-products. The crystal structures (tetragonal, 141/amd (no. 141)), Z = 8, contain two crystallographically independent M3+ Cations that are interconnected by chalcogenide (X2?) and disilicate anions ([Si2O7]6?). (M1)3+ is surrounded by eight (five X2? and three terminal O2? of the disilicate group), (M2)3+ by nine (three X2? and six terminal O2? of the [Si2O7]6? anion) chalcogenide anions. The disilicate anion itself exhibits the eclipsed conformation with non-linear Si? O? Si bridges (angles: 128 – 133°).  相似文献   
8.
 Density functional theory, in combination with a) a careful choice of the exchange-correlation part of the total energy and b) localized basis sets for the electronic orbitals, has become the method of choice for calculating the exchange-couplings in magnetic molecular complexes. Orbital expansion on plane waves can be seen as an alternative basis set especially suited to allow optimization of newly synthesized materials of unknown geometries. However, little is known on the predictive power of this scheme to yield quantitative values for exchange coupling constants J as small as a few hundredths of eV (50–300 cm−1). We have used density functional theory and a plane waves basis set to calculate the exchange couplings J of three homodinuclear Cu-based molecular complexes with experimental values ranging from +40 cm−1 to −300 cm−1. The plane waves basis set proves as accurate as the localized basis set, thereby suggesting that this approach can be reliably employed to predict and rationalize the magnetic properties of molecular-based materials. Corresponding author. E-mail: Carlo.Massobrio@ipcms.u-strasbg.fr Received August 5, 2002; accepted August 9, 2002  相似文献   
9.
Single Crystals of A? Nd2S3, U? Ho2S3, D? Er2S3, and E? Lu2S3 through the Oxidation of Reduced Lanthanide Chlorides with Sulfur The oxidation of reduced chlorides (MCl2) or chloridehydrides (MClHx) of the lanthanides with sulfur (850°C, 7 d, tantalum ampoule) usually results in the formation of their sesquisulfides (M2S3) as the main product. In the presence of appropriate fluxes (e. g., NaCl), they often are obtained as single crystals, and the flux appears to decide which modification is favourized. Single crystals of Nd2S3 , (from NdCl2 + NaCl + S, 2 : 2 : 1, A-type: orthorhombic, Pnma (no. 62), Z = 4; a = 743.97(5), b = 402.78(3), c = 1551.96(9) pm, Vm = 70.015(8) cm3/mol, R , = 0.026, Rw = 0.023), Ho2S3 , (from Na0.25HoClH0.75 + S, 8 : 9, U type: orthorhombic, Pnma (no. 62), Z = 4, a = 1057.24(7), b = 384.48(4), c = 1041.15(7) pm, Vm = 63.716(9) cm3/mol, R , = 0.023, Rw = 0.020), Er2S3 , (from ErClH0.67 + NaCl + S, 2 : 2 : 1, D type: monoclinic, P21/m (no. 11), Z = 6, a = 1744.18(9), b = 398.22(3), c = 1010.13(6) pm, β = 98.688(4)°, Vm = 69.610(7) cm3/mol, R = 0.031, Rw = 0.029) and Lu2S3 , (from LuClH0.67 + NaCl + S, 2 : 2 : 1, E type: trigonal, R3 c (no. 167), Z = 6, a = 672.86(2), c = 1816.84(9) pm, c/a = 2.70, Vm = 71.497(6) cm3/mol, R = 0.023, Rw = 0.020) as well as more systematic general investigations (syntheses of the lanthanide sesquisulfides from the elements in the presence of NaCl as a flux in sealed tantalum containers at 850°C) are the main topic of the work presented here.  相似文献   
10.
By treating Cu(I) complexes of neutral, bidentate N-donor ligands with S8, clusters with novel delocalized mixed-valence [Cu3(mu-S)2]3+ cores have been isolated. X-ray crystal structures and UV-vis and resonance Raman spectral features of these clusters reveal similarities to the tetracopper-sulfide "CuZ" site in nitrous oxide reductase. A delocalized S = 1 ground state for the mixed-valent CuIIICu2II cores is supported by the observation of high symmetry in the X-ray structures and 10-line hyperfine features arising from coupling to three equivalent Cu ions in EPR spectra obtained at room temperature (shown) and 10 K. The delocalization we observe contrasts with the localization reported previously for a [Cu3(mu-O)2]3+ analogue (Root, D. E.; Henson, M. J.; Machonkin, T.; Mukherjee, P.; Stack, T. D. P.; Solomon, E. I. J. Am. Chem. Soc. 1998, 120, 4982), which we rationalized through DFT calculations.  相似文献   
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