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71.
The title compound Rb(14)(Mg(1-x)In(x))(30) (x = 0.79-0.88) has been obtained from high-temperature reactions of the elements in welded Ta tubes. There is no analogous binary compound without Mg. The crystal structure established by single-crystal X-ray diffraction means (space group P2m (No. 189), Z = 1 and a = b = 10.1593(3) Angstroms, c = 17.783(1) Angstroms for x = 0.851) features two distinct types of anionic layers: isolated pentacapped trigonal prismatic In(11)(7-) clusters and condensed [(Mg(x)In(1-x))(5)In(14)](7-) layers. The latter consists of analogous M(11) (M = Mg/In) fragments that share prismatic edges and are interbridged by trigonal M(3) units. The structure shows substantial differences from related A(15)Tl(27) (A = Rb, Cs) in which the cation A that centers a six-membered ring of Tl(11) fragments is replaced by M(3.) Both linear muffin-tin orbital and extended Hückel calculations are used to analyze the observed phase width and site preferences. We further utilize the results to rationalize the distortion of the M(11) fragment in the condensed layer and also to correlate with electrical properties. An isomorphous phase region (Rb(y)K(1-)(y))(14)(Mg(1-x)In(x))(30) (y = 0.52, 0.66 for x = 0.79) is also formed. 相似文献
72.
The ternary compounds K(34)In(91.05(9))Mg(13.95(9)) (I), K(34)In(96.19(6))Au(8.81(6)) (II), and K(34)In(89.95(1))Zn(13.05(7)) (III) have been synthesized by high-temperature means and structurally characterized by single-crystal X-ray diffraction methods. All are analogues of earlier products in which Li is substituted for some In in a hypothetical K(34)In(105) lattice. They consist of complex three-dimensional anionic networks built of In(12) icosahedra and M(28) triply fused icosahedra (M = In or In/T and T = Mg, Au, or Zn). The K atoms bridge between cluster faces or edges and form K(136) clathrate-IotaIota type networks. Two neighboring M(28) units are interconnected by an M atom to form a sandwich complex (M(28))M(M(28)) in I and II or by a Zn-Zn dimer in (M(28))ZnZn(M(28)) in III. Mixed In/T sites only occur in the M(28) portions. Phase stabilization through electronic tuning is present in all three via substitution of the electron-poorer T elements for In. Extended Hückel analyses indicate that all metal-metal bonding within the M(28) cluster appears to be optimized in I and III even though both are metallic. The size of the substituted element is also important in the structural features, as is especially shown by the Zn compound. 相似文献
73.
The title compounds, which are synthesized from be elements, are shown to be isostructural with K8In11 (R3¯c Z=6) and to contain pentacapped trigonal prismatic clusters that have been compressed along the three-fold axes so as to bring the two types of capping atoms within bonding distances. These are arranged in double-ccp layers separated by double alkali--metal layers. Extended Hückel calculations show a substantial energy gap and the end of significant intracluster bonding for the hypoelectronic (by Wade's rules) 18-electron Tl11 7?. Correspondingly, all three compounds are metallic (ρ298 ≈ 400 μΩ · cm) and Pauli-paramagnetic (χM ≈ 4 x 10?4 emu. mol?1, consistent with their formulation as metallic (A +)8Tl11 7? e? phases. Factors thought to be responsible for the cluster distortion, the metallic salt characteristics, and the unusual chemistry of thallium am noted. 相似文献
74.
The title compound forms on fusion and annealing of a stoichiometric mixture of the elements. The structure was determined by single-crystal X-ray diffraction methods in the monoclinic space group C2/c, with a = 15.154(3) A, b = 10.401(2) A, c = 17.413(4) A, and beta = 113.57(3) degrees, Z = 8. Four-membered Tl-Sb1-Sb4-Sb3 rings interlinked by pairs of Sb2 bridges generate swinglike repeat units [Tl(2)Sb(8)] that are further interlinked through external Tl-Tl bonds to form infinite one-dimensional chains. Cations play a major role in the structure. In contrast to the Zintl-phase K(6)Tl(2)Sb(3) with similar swinglike [Tl(4)Sb(6)] repeating units and Tl-Tl interlinkages, Na(6)TlSb(4) has a more compact conformation of the chains and a notably smaller cell volume than expected. The new phase is metallic with two excess cations according to empirical electron counting, EHTB band calculations for the anion, and the compound's measured resistivities and magnetic susceptibilities. The notably shorter Tl-Tl bond in the present salt (2.954 A) can be directly attributed to the smaller cation and reduced intercation repulsions across that bond. 相似文献
75.
The Rb-In system contains only RbIn4 (BaAl4 type) and Rb2In3 in the 0–80 at.% In region. The structure of Rb2In3 consists of rubidium ions between layers of closo-In6 clusters joined into sheets through exo bonds at four coplanar vertices (I4/mmm, a=6.8735 (4) Å, c=15.899 (1) Å, R(F)/Rw=3.2/3.5%). The phase is isostructural with Cs2In3 when a probable error in the earlier space group assignment is corrected. Rb2In3 is a poor conductor (P> 103 μohm · cm) with a temperature-independent magnetic susceptibility of (0 ± 4) x 10?6 emu/mol after core and orbital corrections. The corresponding Zintl phase (closed shell configuration) predicted on the basis of conventional electron counting for the cluster network is supported by extended-Hückel MO calculations. The structures of Rb4In6 and In4Rb show a close, inverse relationship in the same space group. 相似文献
76.
Patel VB Sandhu G Corbett JM Dunn MJ Rodrigues LM Griffiths JR Wassif W Sherwood RA Richardson PJ Preedy VR 《Electrophoresis》2000,21(12):2454-2462
We investigated whether the imposition of chronic alcohol in hypertension leads to greater biochemical and cellular abnormalities of the myocardium than those arising in normotension. Fifteen-week-old spontaneously hypertensive rats (SHR) and Wistar Kyoto (WKY) rats were fed ethanol-containing diets for six weeks. Particular attention was focused on the composition of contractile proteins identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), fractional rate of protein synthesis, and synthesis rates relative to RNA (RNA activity) or DNA (cellular efficiency). In addition, myocardial enzymes and adenine nucleotides were measured. In both SHR and WKY rats chronic ethanol caused a general decrease in the contents of all nine contractile proteins with myosin heavy chain predominantly affected. Fractional rates of mixed (i.e., total) and myofibrillary proteins remained unaltered in both WKY rats and SHR, as were cellular efficiencies. The RNA activity was significantly reduced in ethanol-treated SHR but not in WKY rats. In ethanol-treated SHR, cardiac creatine kinase (CK) and malate dehydrogenase (MDH) activities were increased, AMP levels were elevated, whilst ATP levels and the energy charge were reduced. In WKY rats, the only significant change related to increased aspartate aminotransferase activities in response to alcohol feeding. Although there were only subtle differences between the response of the normotensive and hypertensive rats due to ethanol dosage, the reduced ATP levels and increased CK and MDH activities in SHR may reflect a greater susceptibility to ischaemic damage. Reduced contractile protein content, particularly myosin heavy chain, may contribute to contractile defects, a common feature of subclinical and clinical alcoholic cardiomyopathy. 相似文献
77.
Reactions of KI, Pr, PrI3, and Os in niobium tubes at 800° yielded black, air- and moisture-sensitive crystals of Kpr6I10Os which were characterized by single crystal X-ray diffraction (orthorhombic, Pnma, a = 15.362(3), b = 13.498(2), c = 14.128(3) Å, Z = 4, R(F)/Rw = 4.4/5.6%). Subsequent parallel experiments also gave, according to Guinier powder pattern data, the isostructural compounds CsPr6I10Fe (a = 15.312(2), b = 13.426(1), c = 14.154(1) Å), CsLa6I10Fe (a = 15.523(2), b = 13.646(2), c = 14.334(1) Å) and CsLa6I10Mn (a = 15.457(4), b = 13.737(2), c = 14.329(2) Å). The important structural feature is the presence of octahedral rare-earth-metal cluster units R6 that are centered by a transition-metal atom Z and bridged and interconnected by halide atoms. The new compounds exhibit the same general pattern of halide connectivity (R6Z)XXXX as do the triclinic compounds R6X10Z. However, the structural arrangement of the metal octahedra is significantly different; they are linked by Ii–i atoms into zigzag chains along [010] and these are interconnected into a three dimensional network by Ii–a atoms to form channels in which the alkali-metal atoms are located. The introduction of alkali-metal atoms into reactions leads to new quaternary compounds with discrete rare-earth-metal clusters centered by transition metals and more open structure frameworks. Measurements of the temperature dependencies of the magnetic susceptibilities for CsLa6I10Fe and CsLa6I10Mn are consistent with expectations for 17- and 16-electron cluster systems, respectively. 相似文献
78.
The syntheses and structures of and bonding in the title compounds are described and compared with those for the isostructural orthorhombic Er(7)Ni(2)Te(2) (Imm2) and other related phases. Single-crystal data are reported for Z = Ni, Pd. The condensation of tricapped trigonal prisms (TTP) into sheets and the bridging of these by separate Lu atoms into a 3D structure are described. The interlayer separation, the Lu-Lu bonding achieved, and the polar Lu-Te bonding therewith are all affected by the size and valence energies of Te. The two Te spacers also exist in capped centered Lu(6)Te trigonal prisms. In terms of extended Hückel band analyses, the overall bonding for both Lu-Ni and Lu-Te are optimized energetically, but not for Lu-Lu. The average Lu-Lu overlap populations about each Lu appropriately increase with a decrease in the number of its Te neighbors. 相似文献
79.
Suitable reactions in sealed Nb tubing at 850-950 degrees C gave good yields of a family of oligomeric cluster phases that were characterized by single-crystal X-ray diffraction means. The basic Y(16)Z(4) units ( approximately &fourmacr; symmetry) can be derived from 2+2 condensation of centered Y(6)Br(12)Z-type clusters or as tetracapped truncated tetrahedra Y(16) that are centered by a large tetrahedral Z(4). These are surrounded by 36 bromine atoms which bridge edges or cap faces of the Y(16)Z(4) nuclei and, in part, bridge to metal atoms in other clusters. The principal bonding appears to be Y-Z and Y-Br, with weaker Y-Y (&dmacr; approximately 3.70 ?) and negligible Z-Z interactions. The phase Y(16)Br(20)Ru(4) (P4(2)/nnm, Z = 2; a = 11.662(1) ?, c = 16.992 (2) ?) is isostructural with Y(16)I(20)Ru(4) and with the new Sc(16)Br(20)Z(4) (Z = Fe, Os). Syntheses only in the presence of Ir and ABr-YBr(3) fluxes (A = K-Cs) produce Y(16)Br(24)Ir(4) (Fddd, Z = 8; a = 11.718(3) ?, b = 22.361(7) ?, c = 44.702(2) ?), in which the electron-richer Ir interstitials are compensated by four additional bromine atoms and altered bridging between macroclusters. Larger amounts of YBr(3) yield a third example, Y(20)Br(36)Ir(4) (Y(16)Br(24)Ir(4).4YBr(3), I4(1)a, Z = 4; a = 12.699(1) ?, c = 45.11(1) ?). Here infinite zigzag chains of YBr(6/2) octahedra that share cis edges lie between and bridge to the Y(16)Ir(4) clusters. All of these phases contain 60-electron, closed-shell macroclusters. Y(16)Br(20)Ru(4) and Y(20)Br(36)Ir(4) were found to exhibit temperature-independent (Van Vleck) paramagnetism with values typical of those found for other rare-earth-metal, zirconium, niobium, and tantalum cluster halides. 相似文献
80.
Suitable proportions of La, La4Pb3 and La2O3 or LaN reacted in pressed pellets at 1050°–1250°C result in high yields of the title compounds. Single crystal X-ray studies of the oxide show it to be an isopointal, interstitial derivative of the Cr5B3 structure (I4/mcm, Z = 4, a = 8.6895(2) Å, c = 14.540(1) Å, R/Rw = 3.0/3.5%). Oxygen or nitrogen atoms are bound in (La2)4 tetrahedra within chains along (0, 1 /2, z). Negligible dimerization of the type characteristic of Cr5B3 is indicated by the Pb2? Pb2 separation, 3.550(1) Å. The structure is compared with other related examples. 相似文献