Hydrogen adsorption on the indium-rich indium phosphide (001) surface: a novel way to produce bridging In-H-In bonds

The indium phosphide (001) surface provides a unique chemical environment for studying the reactivity of hydrogen toward the electron-deficient group IIIA element, indium. Hydrogen adsorption on the In-rich delta(2 x 4) reconstruction produced a neutral, covalently bound bridging indium hydride. Using vibrational spectroscopy and ab initio cluster calculations, two types of bridging hydrides were identified, a (mu-H)In(2) and a (mu-H)(2)In(3) "butterfly-like" structure. These structures were formed owing to the large thermodynamic driving force for adsorption of H atoms on solid-state indium dimers.     

Synthesis, structure, and bonding of open-shell Sr3In5: an unusual electron deficiency in an indium network, beyond the Zintl boundary.

The new title compound has been synthesized and characterized by physical property measurements and electronic structure calculations. The results ratify the highly uncommon deficiency of one electron that has been long speculated for its Ca3Ga5-type structure on the basis of the simple Zintl electron counting formalism. In the Sr3In5 structure (Cmcm), 4- and 2-bonded indium atoms in a 4:1 ratio form a three-dimensional classical network that encapsulates strontium atoms in its narrow channels. The electrical conductivity of the compound shows typical metallic behavior. The detailed electronic structure analysis suggests that the electron hole is mainly localized on a nonbonding p-orbital on the 2-bonded indium atoms, and that these orbitals, stacked in a sigma-type way along avector (4.97 A), interact only weakly with each other to form highly one-dimensional bands.     

Synthesis and crystal structure of Ae(2)LiInGe(2) (Ae = Ca, Sr): new Zintl phases with a layered silicate-like network

Two new Zintl phases Ae(2)LiInGe(2) (Ae = Ca 1; Sr 2) were obtained from stoichiometric reactions of the pure elements in sealed Nb tubing at 1000-1050 degrees C. The isomorphous polar intermetallic phases crystallize in the orthorhombic space group Pnma, with cell constants of a = 7.2512(7), b = 4.4380(5), and c = 16.902(1) A for compound 1, and a = 7.5033(8), b = 4.6194(5), and c = 17.473(2) A for compound 2. The crystal structure can be derived from the vertex-sharing of InGe(4/2) tetrahedral units that form "corrugated" sheets normal to the crystallographic c-axis. Calcium and lithium atoms act as "spacers" that effectively separate the anionic [InGe(2)](5-) layers. The layered anionic substructure is similar to those exhibited by layered metal oxides, sulfides, and silicates. The connectivity of the tetrahedral building unit, [InGe(4/2)](5-), is analogous and isoelectronic to the silicate [SiO(4/2)] unit.     

Evidence of incipient bond-stretching isomerism in Sr2.04(1)Ca0.96(1)Sn5 from variable-temperature structural studies

The title compound was found to crystallize in the Pu3Pd5 structure type (SG Cmcm) with cell dimensions of a = 10.5179(9) A, b = 8.4789(8) A, and c = 10.7623(10) A. The structure consists of isolated Sn5(6-) square-pyramidal units surrounded by cations that seem to play a crucial role in stabilizing the Zintl polyanions. The square pyramids contract at low temperatures (100 K) leading to the shortening of the basal intracluster Sn-Sn bond (2.74 A), while the intercluster bonds become very large, indicating features of bond stretching isomerism as is known for Ba3Ge4. A study of different crystals shows a slight variation in the lattice parameters, suggesting the presence of a definite phase width which was substantiated by the successful synthesis of monophasic samples of Sr(3-x)CaxSn5 (0.5 相似文献   

Synthesis, structure, and bonding of Eu3Bi(Sn,Bi)4. A rare inverse-Cr5B3-type structure with a new tin/bismuth network

The ternary phase Eu3Bi(Sn1-xBix)4 ( approximately 0 < x < approximately 0.15) has been synthesized by solid-state methods at high temperature. The crystal structure of the limiting Eu3Bi(Sn3.39Bi0.61(3)) has been determined by single-crystal X-ray analysis to be isopointal with an inverse-Cr5B3-type structure [space group I4/mcm, Z = 4, a = 8.826(1) A, c = 12.564(3) A, and V = 978.6(3) A3]. The structure contains slabs of three-bonded Sn/Bi atoms as puckered eight- and four-membered rings interlinked at all vertices, and these are separated by planar layers of individual Eu and Bi atoms. In the normal (stuffed) Cr5B3-type analogue Eu5Sn3Hx, these two units are replaced by a more highly puckered network of Eu cations around isolated Sn atoms and planar layers of isolated Eu atoms and Sn dimers, respectively. Band structures of limiting models of the phase calculated by TB-LMTO-ASA methods show a metallic character and indicate that the mixed Sn/Bi occupancy in the slabs in this structure for x > 0 probably originates with the electronic advantages of the pseudogap that would occur at the electron count of the ideal Zintl phase Eu3Bi(Sn3Bi). The stability of a competing phase reduces this limit to Eu3Bi(Sn3.4Bi0.6).     

Novel corrugated In9 anionic layer in Li2Y5In9: square pyramidal In5 clusters interconnected by unusual butterfly In4 clusters

The new ternary polar intermetallic phase, Li2Y5In9, was obtained by high-temperature solid-state reactions of the corresponding elements inwelded Ta tubes. Its crystal structure was established by a single-crystal X-ray diffraction study. Li2Y5In9 crystallizes in the tetragonal space group P4/nmm (No. 129) with cell parameters of a = b = 10.1242(4), c = 15.1091(10) A and Z = 4. The structure of Li2Y5In9 features a two-dimensional corrugated anionic In9 layer composed of two types of square pyramidal In5 units and butterfly In4 units. There are two types of square pyramidal In5 units: one with normal In-In bonds and another one with greatly elongated In-In separations within its In4 square. Packing of these 2D In9 layers resulted in cavities and tunnels that are occupied by Y and Li atoms. Extended-Hückel tight-binding calculations indicate that Li2Y5In9 is metallic.     

X-ray and neutron diffraction studies on "Li4.4Sn"

A chemical analysis and detailed structural characterization, using X-ray single crystal and neutron powder diffraction, of the binary lithium-tin compound "Li(4.4)Sn" is presented. Phase analyses and subsequent structural refinements result in the reformulation of "Li(4.4)Sn" as Li(17)Sn(4). The lithium-rich binary phase crystallizes with a complex cubic structure in the space group Ffourmacr;3m, with a = 19.6907(11) A, Z = 20. The improved crystal structure determination indicates well-defined lithium atom positions, some of which differ from those previously reported. The nearly Zintl phase Li(17)Sn(4) exhibits poor metallic behavior similar to that of heavily doped semiconductors. Comparisons of the refined crystal structure with previously reported X-ray crystal structures associated with "Li(4.4)Sn" are discussed.     

A(15)Tl(27) (A = Rb, Cs): A Structural Type Containing Both Isolated Clusters and Condensed Layers Based on the Tl(11) Fragment. Syntheses, Structure, Properties, and Band Structure

The isomorphous title compounds (and the ordered substitutional Rb(14)CsTl(27)) are obtained directly from reactions of the elements in sealed Ta below approximately 330 degrees C. Refinements of single-crystal data for the three established a structure with alternate layers of isolated pentacapped trigonal prismatic Tl(11)(7)(-) (D(3)(h)()) ions and condensed [Tl(16)(8-)] networks that are separated by cations. The condensed layer consists of Tl(11) units that share prismatic edges and are interbridged through waist-capping atoms (Tl(6/2)Tl(3)Tl(2)). (Rb(15)Tl(27): P&sixmacr;2m, Z = 1, a = 10.3248(6) ?, c = 17.558(2) ?.) The rubidium phase is a poor metal (rho(293) approximately 34 &mgr;Omega.cm) and is Pauli-paramagnetic. Extended Hückel band calculations indicate partially filled bands and a non-zero DOS at E(F), consistent with the observed metallic behavior, although appropriate cation tuning or modest anion doping should provide a Zintl phase. The band structure and COOP curves are also used to rationalize the distortion of the Tl(11) unit on condensation and the critical role of the interfragment bonds between waist-capping atoms in stabilizing the layer.     

M2Ba2Sn6 (m =yb, ca): metallic zintl phases with a novel tin chain substructure

The compounds M2Ba2Sn6 (M = Yb, Ca) have been synthesized by solid-state reactions in welded Ta tubes at high temperature. Their structures were determined by single-crystal X-ray diffraction studies to be orthorhombic; space group Cmca (No. 64); Z = 8; a = 15.871(3), 15.912 (3) A; b = 9.387(2), 9.497(2) A; c = 17.212(3), 17.184(3) A; and V = 2564.3(9), 2597.0(9) A3, respectively. These contain infinite tin chains along constructed from butterflylike 3-bonded Sn tetramers interconnected by pairs of 2-bonded Sn. The chains are further interconnected into corrugated layers by somewhat longer Sn-Sn bonds along c. The compounds with the chains alone would be Zintl phases, but the interchain bonding makes them formally one-electron rich per formula unit. The electronic structures calculated by extended Hückel and TB-LMTO-ASA methods indicate that these compounds are metallic but with a deep pseudogap at the Fermi level. States that bind the extra electrons lie just below EF and involve important Yb(Ca)-Sn contributions. The origin of metallic Zintl phases is briefly discussed.     

Electron-precise/deficient La(5-x)Ca(x)Ge4 (3.4 < or = x < or = 3.8) and Ce(5-x)Ca(x)Ge4 (3.0 < or = x < or = 3.3): probing low-valence electron concentrations in metal-rich Gd5Si4-type germanides

We report for the first time the syntheses of electron-precise/deficient alloys, Ln5-xCaxGe4 (Ln = La, Ce; x = 3.37, 3.66, 3.82 for La; x = 3.00, 3.20, 3.26 for Ce), in the metal-rich R5Tt4 Zintl system (R = rare earth metal; Tt = Si, Ge). The new alloys extend the phase width from electron-rich to open-shell electron-deficient region in the metal-rich Zintl system and demonstrate possible occurrence of varied electron deficiencies in Zintl phases without structural changes, as a result of other existing structure-forming factors.     

Synthesis, Structure, and Bonding of Two Lanthanum Indium Germanides with Novel Structures and Properties

The new tetragonal phases La(3)In(4)Ge and La(3)InGe are obtained from high-temperature reactions of the elements in welded Ta followed by annealing. The structures of both were established by single-crystal X-ray diffraction in tetragonal space group I4/mcm (Z = 4 and 16, a = 8.5165(3) and 12.3083(2) ?, c = 11.9024(4) and 16.0776(4) ?, respectively). La(3)In(4)Ge contains layers or slabs of three-connected indium built of puckered 8-rings and 4-rings, or of squashed tetrahedra ("butterflies") interlinked at all vertices, and these are separated by layers of La and isolated Ge. The phase is deficient of being a Zintl phase by three electrons per formula unit and is better described in terms of an alternate optimized and delocalized bonding picture and an open-shell metallic behavior for the In slabs. The more complex La(3)InGe, isostructural with Gd(3)Ga(2), is also layered. This phase contains pairs of mixed-occupancy (0.75 In, 0.25 Ge) sites separated by 3.020 ?, as well as isolated In and Ge atoms. The former appear to be fully reduced closed-shell atoms (relative to the bonded Ga dimers in Gd(3)Ga(2)) that are held in somewhat close proximity by cation matrix effects. The compound appears to be semiconducting and thus is a classical Zintl phase, (La(+3))(3)In(-5)Ge(-4) in the simplest oxidation state notation. High Coulomb energies are presumably important for the nature of the bonding and the stabilities of both compounds.     

Unusual electronic and bonding properties of the Zintl phase Ca5Ge3 and related compounds. A theoretical analysis

Theoretical reasons for metallic behavior among diverse Zintl phases have generally not been pursued at an advanced level. Here, the electronic structure of Ca5Ge3 (Cr5B3 type), which can be formulated (Ca+2)5(Ge2-6)Ge-4 in oxidation states, has been explored comparatively by means of semiempirical and first-principles density functional methods. The FP-APW calculations show that alkaline-earth-metal and germanium orbitals, particularly the d orbitals on the cations and the p-pi orbitals of the halogen-like dimeric Ge2-6, mix considerably to form a conduction band. This covalency perfectly explains the unusual metallic properties of the nominally electron-precise Zintl phase Ca5Ge3 and its numerous relatives. Similar calculational results are obtained for Sr5Ge3, Ba5Ge3, and Ca5Sn3. Cation d orbitals appear to be a common theme among Zintl phases that are also metallic.     

New tetragonal structure type for A2Ca10S(9 (A = Li, Mg). Electronic variability around a Zintl phase

The phases LiMgCa(10)Sb(9) (1), Mg(2)Ca(10)Sb(9) (2), and Li(1.38(2))Ca(10.62)Sb(9) (3) have been synthesized by high-temperature solid-state means and characterized by single-crystal means and property measurements. These occur in space group P4(2)/mnm, Z = 4, with a = 11.8658(5), 11.8438(6), 11.9053(7) Angstroms and c = 17.181(2), 17.297(2), 17.152(2) Angstroms, respectively. The two types of A atoms occupy characteristic sites in a Ca-Sb network that contains a 5:2 proportion of (formal) Sb(3-) and Sb(2)(4-) anions and can be described in terms of two slab types stacked along [001]. Bonding appears to be strong in these salts with generally normal distances and high coordination numbers except for the 4-bonded atoms in a C(2)(v) position for the second type of A that is occupied by Li, Mg or Ca(0.62(2))Li(0.38), respectively. The three compounds are, respectively, an ideal electron-precise Zintl phase, one e(-)-rich and 0.40(4) e(-)-short per formula unit. The LiMgCa(10)Sb(9) compound is correspondingly diamagnetic and presumably a semiconductor.     

Structural diversity in solvated lithium aryloxides. Syntheses, characterization, and structures of [Li(OAr)(THF)x]n and [Li(OAr)(py)x]2 complexes where OAr = OC6H5, OC6H4(2-Me), OC6H3(2,6-(Me))2, OC6H4(2-Pr(i)), OC6H3(2,6-Pr(i)))2, OC6h4(2-Bu(t)), OC6H3(2,6-Bu(t)))2

A series of sterically varied aryl alcohols H-OAr [OAr = OC6H5 (OPh), OC6H4(2-Me) (oMP), OC6H3(2,6-(Me))2 (DMP), OC6H4(2-Pr(i)) (oPP), OC6H3(2,6-(Pr(i)))2 (DIP), OC6H4(2-Bu(t)) (oBP), OC6H3(2,6-(Bu(t)))2 (DBP); Me = CH3, Pr(i) = CHMe2, and Bu(t) = CMe3] were reacted with LiN(SiMe3)2 in a Lewis basic solvent [tetrahydrofuran (THF) or pyridine (py)] to generate the appropriate "Li(OAr)(solv)x". In the presence of THF, the OPh derivative was previously identified as the hexagonal prismatic complex [Li(OPh)(THF)]6; however, the structure isolated from the above route proved to be the tetranuclear species [Li(OPh)(THF)]4 (1). The other "Li(OAr)(THF)x" products isolated were characterized by single-crystal X-ray diffraction as [Li(OAr)(THF)]4 [OAr = oMP (2), DMP (3), oPP (4)], [Li(DIP)(THF)]3 (5), [Li(oBP)(THF)2]2, (6), and [Li(DBP)(THF)]2, (7). The tetranuclear species (1-4) consist of symmetric cubes of alternating tetrahedral Li and pyramidal O atoms, with terminal THF solvent molecules bound to each metal center. The trinuclear species 5 consists of a six-membered ring of alternating trigonal planar Li and bridging O atoms, with one THF solvent molecule bound to each metal center. Compound 6 possesses two Li atoms that adopt tetrahedral geometries involving two bridging oBP and two terminal THF ligands. The structure of 7 was identical to the previously reported [Li(DBP)(THF)]2 species, but different unit cell parameters were observed. Compound 7 varies from 6 in that only one solvent molecule is bound to each Li metal center of 7 because of the steric bulk of the DBP ligand. In contrast to the structurally diverse THF adducts, when py was used as the solvent, the appropriate "Li(OAr)(py)x" complexes were isolated as [Li(OAr)(py)2]2 (OAr = OPh (8), oMP (9), DMP (10), oPP (11), DIP (12), oBP (13)) and [Li(DBP)(py)]2 (14). Compounds 8-13 adopt a dinuclear, edge-shared tetrahedral complex. For 14, because of the steric crowding of the DBP ligand, only one py is coordinated, yielding a dinuclear fused trigonal planar arrangement. Two additional structure types were also characterized for the DIP ligand: [Li(DIP)(H-DIP)(py)]2 (12b) and [Li2(DIP)2(py)3] (12c). Multinuclear (6,7Li and 13C) solid-state MAS NMR spectroscopic studies indicate that the bulk powder possesses several Li environments for "transitional ligands" of the THF complexes; however, the py adducts possess only one Li environment, which is consistent with the solid-state structures. Solution NMR studies indicate that "transitional" compounds of the THF precursors display multiple species in solution whereas the py adducts display only one lithium environment.     

Structure of BaGd2（MoO4）4 Crystal

The title compound belongs to monoclinic,space group C2/c with a=5.2694(1),b=12.6659(4),c=19.4108(2) ,β=91.504(2)°,V=1295.06(5) 3,Z=4 and Dc=5.599 g/cm3. The structure of BaGd2(MoO4)4 contains a MoO4 tetrahedron,a distorted GdO8 polyhedron,and Ba2+ ions in a tenfold coordination. The GdO8 polyhedra are linked together through edge-sharing to give a two-dimensional Gd layer. The MoO4 tetrahedra connected to the Gd atoms are capped up and down the Gd layer through common oxygen apices,thus forming a new Gd-Mo layer. Finally,the Gd-Mo layers are held together through bridging BaO10 polyhedra to form a three-dimensional framework. Since the Ba-μ3-O bond has a large average distance of 2.888 ,this structural characteristic will result in a cleavage along the (001) plane.     

Synthesis,Structure and Luminescent Property of a New Cd(Ⅱ) Complex Containing 2-Propyl-imidazole-4,5-dicarboxylate

A new Cd(Ⅱ) complex([Cd(H2PIDC)2]n) with singly deprotonated 2-propyl-imidazole-4,5-dicarboxylate as bridging ligand was synthesized and characterized by X-ray diffraction method.Crystal data:monoclinic,space group P21/c,with a=8.2547(11),b=10.7071(15),c=13.9131(14),β=126.164(5)o,V=992.8(2)3,C16H18N4O8Cd,Mr=506.74,Z=2,Dc=1.695g/cm3,F(000)=508,μ=1.151 mm-1,R=0.0296 and wR=0.0812 for 1581 observed reflections.Singly deprotonated ligands(H2PIDC-) act as μ3-bridge and join the Cd(Ⅱ) atoms into a 2-D layer structure.The 2-D layers are further linked by intermolecular hydrogen bonds into a 3D network.The luminescent property of the complex was also investigated.     

Metallic behavior of the Zintl phase EuGe2: combined structural studies, property measurements, and electronic structure calculations

The Zintl compound EuGe₂ crystallizes in the trigonal space group (No. 164) with the CeCd₂-structure type. Its structure can be formally derived from the hexagonal AlB₂-structure type by a strong puckering of the hexagonal layers. The chemical bonding in EuGe₂ can be rationalized according to the Zintl concept as (Eu²⁺)(Ge¹⁻)₂, since the europium atoms are divalent and each germanium atom receives one additional valence electron. In that sense, EuGe₂ is expected to be a closed-shell compound with semiconducting behavior. However, temperature dependent resistivity measurements show EuGe₂ to be metallic. Subsequently, detailed crystallographic studies revealed the structure and the composition of EuGe₂ to be free of defects and impurities, which, along with the confirmed divalent oxidation state of the europium atoms by means of magnetic measurements, make EuGe₂ another example of a metallic Zintl phase. These results are in good agreement with the results of electronic structure calculations such as TB-LMTO-ASA (LDA) and FLAPW (GGA), which reveal non-zero DOS at the Fermi level.     

Synthesis and structure of [K(+)-(2,2)diaza-[18]-crown-6][K3Ge9]-2ethylenediamine: stabilization of the two-dimensional layer (2)(infinity)[K3Ge9(1-)

Large bright-red, transparent crystalline plates of [K-(2,2)diaza-[18]-crown-6]K3Ge9-2en are obtained, in high-yield, from a reaction of (2,2)diaza-[18]-crown-6 in toluene with a solution of K4Ge9/potassium metal (K) in ethylenediamine (en). The compound crystallizes in the monoclinic space group P2(1)/m (a = 10.740(1) A, b = 15.812(1) A, c = 12.326(1) A, beta = 114.74 degrees; Z = 2). The crystal structure of [K-(2,2)diaza-[18]-crown-6]K3Ge9-2en features two-dimensional [K3Ge9] layers formed by uncomplexed K(+) cations and Ge94(-) anions. The "not-so-bare" cluster compound features a unique Ge94(-) cluster that exhibits a slightly distorted C(2v) geometry that is closer to D(3h) than the expected C(4v). Use of noncryptand sequestering agents in the isolation of Ge cluster anions from en solutions opens new avenues in understanding important cation-anion interactions in the stability and reactivity of Zintl ions, as well as a viable route to isolating Zintl anions with higher charges per atom.     

Structure and Properties of a New Rare-earth Borate LiSrY_2（BO_3）_3

The structure of LiSrY2(BO3)3 has been solved by single-crystal X-ray diffraction analysis at 298 and 113 K on different diffractometers.It crystallizes in trigonal with space group P-3m1(No.164).The cell parameters at room temperature are as follows:a = 10.3345(9),c = 6.4049(11) ,V = 592.41(13) 3,Z = 3,Mr = 448.81,F(000) = 618,μ = 21.327 mm-1 and Dc = 3.774 g/cm3.The crystal structure consists of gear-like [BY6O33] groups which are linked together by corner-sharing to form a two-dimensional layer parallel to the ab plane.These layers are connected one after another by sharing oxygen atoms with B(2) atoms along the c direction to construct a three-dimensional framework.Li and Sr atoms just occupy the cavities formed by oxygen atoms.In addition,the vibrational spectroscopy of LiSrY2(BO3)3 and photoluminescence properties of the Eu3+ doped LiSrY2(BO3)3 were also studied.