Gold derivatives of eight rare-earth-metal-rich tellurides: monoclinic R7Au2Te2 and orthorhombic R6AuTe2 types

Two series of rare-earth-metal (R) compounds, R(7)Au(2)Te(2) (R = Tb, Dy, Ho) and R(6)AuTe(2) (R = Sc, Y, Dy, Ho, Lu), have been synthesized by high-temperature techniques and characterized by X-ray diffraction analyses as monoclinic Er(7)Au(2)Te(2)-type and orthorhombic Sc(6)PdTe(2)-type structures, respectively. Single-crystal diffraction results are reported for Ho(7)Au(2)Te(2), Lu(6)AuTe(2), Sc(6)Au(0.856(2))Te(2), and Sc(6)Au(0.892(3))Te(2). The structure of Ho(7)Au(2)Te(2) consists of columns of Au-centered tricapped trigonal prisms (TCTPs) of Ho condensed into 2D zigzag sheets that are interbridged by Te and additional Ho to form the 3D network. The structure of Lu(6)AuTe(2) is built of pairs of Au-centered Lu TCTP chains condensed with double Lu octahedra in chains into 2D zigzag sheets that are separated by Te atoms. Tight binding-linear muffin-tin orbital-atomic sphere approximation electronic structure calculations on Lu(6)AuTe(2) indicate a metallic property. The principal polar Lu-Au and Lu-Te interactions constitute 75% of the total Hamilton populations, in contrast to the small values for Lu-Lu bonding even though these comprise the majority of the atoms. A comparison of the theoretical results for Lu(6)AuTe(2) with those for isotypic Lu(6)AgTe(2) and Lu(6)CuTe(2) provides clear evidence of the greater relativistic effects in the bonding of Au. The parallels and noteworthy contrasts between Ho(7)Au(2)Te(2) (35 valence electrons) and the isotypic but much electron-richer Nb(7)P(4) (55 valence electrons) are analyzed and discussed.     

Two-dimensional metallic chain compounds Y5M2Te2 (M = Fe, Co, Ni) that are related to Gd3MnI3. The hydride derivative Y5Ni2Te2D0.4

Y(5)M(2)Te(2) (M = Fe, Co, Ni) have been prepared by high-temperature solid-state techniques and shown to be isostructural and orthorhombic Cmcm (No. 63), Z = 4. The structure was established by single crystal X-ray methods at 23 degrees C for M = Fe, with a = 3.9594(3) A, b = 15.057(1) A, and c = 15.216(1) A. The new structure contains zigzag chains of the late transition metal sheathed by a column of yttrium atoms that are in turn condensed through trans vertices on the latter to yield 2D bimetallic layers separated by single layers of tellurium atoms. Reaction of hydrogen with Y(5)Ni(2)Te(2) causes a rumpling of the Y-Ni layers as determined by both single X-ray crystal means at 23 degrees C and neutron powder diffraction at -259 degrees C for Y(5)Ni(2)Te(2)D(0.41(1)), Pnma (No. 62), Z = 4. Lattice constants from the former study are a = 14.3678(7) A, b = 4.0173(2) A, and c = 15.8787(7) A. The hydrogen is accommodated in tetrahedral yttrium cavities generated by bending the formerly flat sheets at the trans Y vertices. A higher hydride version also exists. Band structure calculations confirm the 2D metal-bonded character of the compounds and also help illustrate the bonding/matrix changes that accompany the bonding of hydrogen. The ternary structures for both Y(5)M(2)Te(2) and Sc(5)Ni(2)Te(2) can be derived from that of Gd(3)MnI(3), the group illustrating three different kinds of metal chain condensation.     

Rb(4)Hg(5)(Te(2))(2)(Te(3))(2)Te(3), [Zn(en)3](4)In(16)(Te2)4(Te3)Te22, and K2Cu2(Te2)(Te3): novel metal polytellurides with unusual metal-tellurium coordination

Three novel metal polytellurides Rb(4)Hg(5)(Te(2))(2)(Te(3))(2)Te(3) (I), [Zn(en)(3)](4)In(16)(Te(2))(4)(Te(3))Te(22) (II), and K(2)Cu(2)(Te(2))(Te(3)) (III) have been prepared by solvothermal reactions in superheated ethylenediamine at 160 degrees C. Their crystal structures have been determined by single-crystal X-ray diffraction techniques. Crystal data for I: space group Pnma, a = 9.803(2) A, b = 9.124(2) A, c = 34.714(7) A, Z = 4. Crystal data for II: space group C2/c, a = 36.814(7) A, b = 16.908(3) A, c = 25.302(5) A, beta = 128.46(3) degrees, Z = 4. Crystal data for III: space group Cmcm, a = 11.386(2) A, b = 7.756(2) A, c = 11.985(2) A, Z = 4. The crystal structure of I consists of 1D infinite ribbons of [Hg(5)(Te(2))(2)(Te(3))(2)Te(3)](4-), which are composed of tetrahedral HgTe(4) and trigonal HgTe(3) units connected through the bridging Te(2-), (Te(2))(2-), and (Te(3))(2-) ligands. II is a layered compound containing InTe(4) tetrahedra that share corners and edges via Te, Te(2), and Te(3) units to form a 2D slab that contains relatively large voids. The [Zn(en)(3)](2+) template cations are filled in these voids and between the slabs. The primary building blocks of III are CuTe(4) tetrahedra that are linked by intralayer (Te(3))(2-) and interlayer (Te(2))(2-) units to form a 3D network with open channels that are occupied by the K(+) cations. All three compounds are rare polytelluride products of solvothermal reactions that contain both Te(2) and Te(3) fragments with unusual metal-tellurium coordination.     

Synthesis, structure, and bonding of Sc(6)MTe(2) (M = Ag, Cu, Cd): heterometal-induced polymerization of metal chains in Sc(2)Te

Three new compounds, Sc(6)AgTe(2), Sc(6)Cu(0.80(2))Te(2.20(2)), and Sc(6)CdTe(2), were prepared by high-temperature solid state techniques, and the structures were determined by single-crystal X-ray diffraction to be orthorhombic, Pnma (No. 62, Z = 4) with a = 20.094(9) A, 19.853(5) A, 20.08(1) A, b = 3.913(1) A, 3.914(1) A, 3.915(2) A, and c = 10.688(2) A, 10.644(2) A, 10.679(5) A, respectively, at 23 degrees C. The compounds are isotypic with Sc(6)PdTe(2) and represent the first ternary metal-rich rare-earth-metal chalcogenides containing group 11 or group 12 elements. The structure can be viewed as heterometal sheets lying parallel to the b-c planes that are separated by isolated tellurium atoms. These sheets can also be viewed as a polymerization of two different types of metal chains in Sc(2)Te (blades and zigzag chains) by heterometal (M) replacements of some intervening tellurium atoms. Extended Hückel band calculations reveal that the interior atoms in the metal network achieve negative formal Mulliken charges while Sc atoms on the exterior that have tellurium neighbors have positive values. The heterometal-metal bonding enhances the overlap populations of zigzag chains and blades relative to those in Sc(2)Te. The calculation results also indicate that these compounds are metallic, as usual.     

R(6)TT'(2), new variants of the Fe(2)P structure type. Sc(6)TTe(2) (T = Ru, Os, Rh, Ir), Lu(6)MoSb(2), and the anti-typic Sc(6)Te(0.80)Bi(1.68)

The Fe(2)P structure (P62m) features two 3-fold Fe positions and both 2-fold and 1-fold P sites, and variations in occupancies of the latter pair yield the reported diversity of results. The known Sc(6)TTe(2) examples for T = Fe-Ni are herein extended to four heavier transition metal T derivatives. An attempt to synthesize bismuth analogues led to the novel inverse derivative in which fractional Te (vice T) occupies the smaller tricapped trigonal prismatic (TTP) Sc polyhedron, and Bi rather than Te occurs in the larger TTP of Sc, with parallel reversal of polarity in the bonding. The reported Lu(8)Te, which is distributed as Lu(6)TeLu(2), is the only example in which a transition metal occupies the normal 2-fold P or Te non-metal position, with corresponding large effects on the bonding. Lutetium otherwise does not form R(6)TTe(2) analogues, but the novel Lu(6)MoSb(2) isotype occurs instead. Extended Hückel calculations are presented for five examples, and the structural and bonding regularities and varieties are discussed further.     

Sc6MTe2 (M = Mn, Fe, Co, Ni): members of the flexible Zr6CoAl2-type family of compounds

The compounds Sc6MTe2 (M = Mn, Fe, Co, Ni) have been prepared by high-temperature solid-state techniques and their structures determined to be hexagonal P62m (No. 189), Z = 1, a = 7.662(1) A, 7.6795(2) A, 7.6977(4) A, 7.7235(4) A and c = 3.9041(9) A, 3.8368(2) A, 3.7855(3) A, 3.7656(3) A for M = Mn, Fe, Co, and Ni, respectively. Crystal structures were refined for M = Fe and Ni, while M = Mn and Co were assigned as isostructural on the basis of powder diffraction data. The Sc6MTe2 compounds belong to a large family with the Zr6CoAl2-type structure, an ordered variant of the Fe2P structure. The structure contains confacial tricapped trigonal prisms of scandium centered alternately by the late transition metal or tellurium atoms. The Sc6MTe2 compounds are the electron-poorest examples of this structure type. Extended Hückel band calculations for M = Fe and Ni show that both compounds exhibit largely 1D metal-metal bonding and are predicted to be metallic.     

Synthesis and Structure of the Layered Thorium Telluride CsTh(2)Te(6)

The compound CsTh(2)Te(6) has been synthesized at 800 degrees C by the reaction of Th with a Cs(2)Te(3)/Te melt as a reactive flux. The compound crystallizes in the space group -Cmcm of the orthorhombic system with two formula units in a cell of dimensions a = 4.367(2) ?, b = 25.119(10) ?, c = 6.140(3) ?, and V = 673.5(5) ?(3) at T = 113 K. The structure of CsTh(2)Te(6) has been determined from single-crystal X-ray data. The structure comprises infinite, two-dimensional double layers of ThTe(8)-bicapped trigonal prisms. The structural motif of the trigonal prisms resembles that found in UTe(2). Cs(+) cations, disordered equally over two crystallographically equivalent sites, separate the layers and are coordinated by eight Te atoms at the corners of a rectangular parallelepiped. Short Te-Te distances of 3.052(3) and 3.088(3) ? form linear, infinite, one-dimensional chains within the layers. Simple formalisms describe neither the Te-Te bonding in the chain nor the oxidation state of Th. The compound shows weak semiconducting behavior along the Th/Te layers perpendicular to the Te-Te chain.     

Expanding the remarkable structural diversity of uranyl tellurites: hydrothermal preparation and structures of K[UO(2)Te(2)O(5)(OH)], Tl(3)[(UO(2))(2)[Te(2)O(5)(OH)](Te(2)O(6))].2H(2)O,beta-Tl(2)[UO(2)(TeO(3))(2)], and Sr(3)[UO(2)(TeO(3))(2)](TeO(3))(2)

The reactions of UO(2)(C(2)H(3)O(2))(2).2H(2)O with K(2)TeO(3).H(2)O, Na(2)TeO(3) and TlCl, or Na(2)TeO(3) and Sr(OH)(2).8H(2)O under mild hydrothermal conditions yield K[UO(2)Te(2)O(5)(OH)] (1), Tl(3)[(UO(2))(2)[Te(2)O(5)(OH)](Te(2)O(6))].2H(2)O (2) and beta-Tl(2)[UO(2)(TeO(3))(2)] (3), or Sr(3)[UO(2)(TeO(3))(2)](TeO(3))(2) (4), respectively. The structure of 1 consists of tetragonal bipyramidal U(VI) centers that are bound by terminal oxo groups and tellurite anions. These UO(6) units span between one-dimensional chains of corner-sharing, square pyramidal TeO(4) polyhedra to create two-dimensional layers. Alternating corner-shared oxygen atoms in the tellurium oxide chains are protonated to create short/long bonding patterns. The one-dimensional chains of corner-sharing TeO(4) units found in 1 are also present in 2. However, in 2 there are two distinct chains present, one where alternating corner-shared oxygen atoms are protonated, and one where the chains are unprotonated. The uranyl moieties in 2 are bound by five oxygen atoms from the tellurite chains to create seven-coordinate pentagonal bipyramidal U(VI). The structures of 3 and 4 both contain one-dimensional [UO(2)(TeO(3))(2)](2-) chains constructed from tetragonal bipyramidal U(VI) centers that are bridged by tellurite anions. The chains differ between 3 and 4 in that all of the pyramidal tellurite anions in 3 have the same orientation, whereas the tellurite anions in 4 have opposite orientations on each side of the chain. In 4, there are also additional isolated TeO(3)(2-) anions present. Crystallographic data: 1, orthorhombic, space group Cmcm, a = 7.9993(5) A, b = 8.7416(6) A, c = 11.4413(8) A, Z = 4; 2, orthorhombic, space group Pbam, a = 10.0623(8) A, b = 23.024(2) A, c = 7.9389(6) A, Z = 4; 3, monoclinic, space group P2(1)/n, a = 5.4766(4) A, b = 8.2348(6) A, c = 20.849(3) A, beta = 92.329(1) degrees, Z = 4; 4, monoclinic, space group C2/c, a = 20.546(1) A, b = 5.6571(3) A, c = 13.0979(8) A, beta = 94.416(1) degrees, Z = 4.     

C(6)H(5)NH(CH(3))(2)](2)Te(2)I(10): secondary I...I bonds build up a 3D network

The crystal structure of [C(6)H(5)NH(CH(3))(2)](2)Te(2)I(10) consists of the N,N-dimethylanilinium cation and a hitherto unreported tellurium iodide anion Te(2)I(10)(2)(-) [crystal data: C(8)H(12)NTeI(5), monoclinic, P2(1)/c, a = 9.4787(2) A, b = 14.2874(3) A, c = 13.6869(3) A, beta = 95.1918(8) degrees, V = 1845.96(7) A(3), Z = 4]. The Te(2)I(10)(2)(-) dianion is based on two edge-sharing TeI(6)(2)(-) octahedra, and interestingly, it builds up a three-dimensional Te(IV)-I open framework through extensive interconnecting I.I contacts. These I.I contacts (3.66-3.80 A) are significantly shorter than the corresponding sum of van der Waals radii (4.0 A) and may potentially promote charge carrier migration throughout the Te-I network. This material can also be drop-cast into thin films from a heated DMF solution.     

Crystal structures and thermal and electrical properties of the new silver (poly)chalcogenide halides Ag23Te12Cl and Ag23Te12Br

Two new silver (poly)chalcogenide halides, Ag23Te12Cl and Ag23Te12Br, were characterized by powder X-ray phase analysis, energy dispersive X-ray analysis, and crystal structure determinations at various temperatures. Thermal analyses of both compounds and electrochemical measurements for the bromide completed the investigation. The compounds Ag23Te12X (X = Cl, Br) are isostructural and crystallize orthorhombically (space group Pnnm, Z = 4) as systematic twins. The lattice parameter values derived from X-ray powder data were a = 21.214(2) A, b = 21.218(2) A, c = 7.7086(7) A, and V = 3469.8(6) A (3) for Ag23Te12Cl at 293 K and a = 21.170(1) A, b = 21.170(1) A, c = 7.7458(5) A, and V = 3471.4(4) A (3) for Ag23Te12Br at 298 K. An enhanced silver ion mobility was revealed by impedance spectroscopy investigations. No phase transitions were observed in the temperature range 100-750 K. These two silver(I) (poly)chalcogenide halides are the second set of representatives of a new class of coinage-metal (poly)chalcogenide halides in which both covalently bonded [Te2](2-) dumbbells and ionically bonded Te(2-) anions appear.     

Neutral tellurium rings in the coordination polymers [Ru(Te9)](InCl4)2, [Ru(Te8)]Cl2, and [Rh(Te6)]Cl3

Shiny black, air‐insensitive crystals of tellurium‐rich one‐dimensional coordination polymers were synthesized by melting a mixture of the elements with TeCl₄. The compounds [Ru(Te₉)](InCl₄)₂ and [Ru(Te₈)]Cl₂ crystallize in the monoclinic space group type C2/c, whereas [Rh(Te₆)]Cl₃ adopts the trigonal space group type R$\bar 3Shiny black, air-insensitive crystals of tellurium-rich one-dimensional coordination polymers were synthesized by melting a mixture of the elements with TeCl(4). The compounds [Ru(Te(9))](InCl(4))(2) and [Ru(Te(8))]Cl(2) crystallize in the monoclinic space group type C2/c, whereas [Rh(Te(6))]Cl(3) adopts the trigonal space group type R ?3c. In the crystal structures, linear, positively charged [M(m+) (Te(n)(±0))] (M=Ru, m=2; Rh, m=3) chains run parallel to the c axes. Each of the uncharged Te(n) molecules (n=6, 8, 9) coordinates two transition-metal atoms as a bridging bis-tridentate ligand. Because the coordinating tellurium atoms act as electron-pair donors, the 18-electron rule is fulfilled for the octahedrally coordinated transition-metal cations. Based on DFT calculations, the quantum theory of atoms in molecules (QTAIM) and the electron localizability indicator (ELI) provide insight into the principles of the polar donor bonding in these complexes. Comparison with optimized ring geometries reveals substantial tension in the coordinating tellurium molecules.     

Isomeric metamorphosis: Si3E (E = S, Se, and Te) bicyclo[1.1.0]butane and cyclobutene

Group 14 and 16 hybrid heavy bicyclo[1.1.0]butanes (tBu2MeSi)4Si3E (E = S, Se, and Te) 2a-c have been prepared by the [1 + 2] cycloaddition reaction of trisilirene 1 and the corresponding chalcogen. Bicyclo[1.1.0]butanes 2 have exceedingly short bridging Si-Si bonds (2.2616(19) A for 2b and 2.2771(13) A for 2c), a phenomenon explained by the important contribution of the trisilirene-chalcogen pi-complex character to the overall bonding of 2. Photolysis of 2a and 2b produced their valence isomers, the heavy cyclobutenes 3a and 3b, featuring flat four-membered Si3E rings and a planar geometry of the Si=Si double bond. The mechanism of such isomerization was studied using deuterium-labeled 2a-d6 to ascertain the preference of the pathway, involving the direct concerted symmetry-allowed transformation of bicyclo[1.1.0]butane 2 to cyclobutene 3.     

Synthesis and characterization of HN(SPiPr2)(SePPh2) and [Te[N(SPiPr2)(SePPh2)]2

The compound HN(SP(i)Pr(2))(SePPh(2)) has been synthesized from the reaction of Ph(2)P(Se)NH(2) with (i)()Pr(2)P(S)Cl in the presence of NaH in THF. HN(SP(i)Pr(2))(SePPh(2)) crystallizes with eight formula units in space group Pbca of the orthorhombic system in a cell of dimensions at -120 degrees C of a = 9.9560(6) A, b = 17.9053(10) A, c = 22.4156(13) A, and V = 3995.9(4) A(3). The square-planar Te(II) complex [Te[N(SP(i)Pr(2))(SePPh(2))](2)] has been isolated from the reaction of Te(tu)(4)Cl(2) x 2H(2)O (tu = thiourea) with the anion [N(SP(i)Pr(2))(SePPh(2))](-), generated in situ from HN(SP(i)Pr(2))(SePPh(2)) in the presence of KO(t)Bu. [Te[N(SP(i)Pr(2))(SePPh(2))](2)] is dimorphic, crystallizing with one formula unit in space group P1 of the triclinic system in a cell of dimensions at -120 degrees C of a = 9.8476(9) A, b = 10.3296(9) A, c = 11.3429(10) A, alpha = 101.903(1) degrees, beta = 115.471(1) degrees, gamma = 92.281(2) degrees, and V = 1008.4(2) A(3) and also crystallizing with two formula units in space group P2(1)/n of the monoclinic system in a cell of dimensions at -120 degrees C of a = 8.7931(5) A, b = 17.1830(10) A, c = 14,1026(9) A, beta = 104.696(1) degrees, and V = 2061.1(2) A(3). In each instance, the [Te[N(SP(i)Pr(2))(SePPh(2))](2)] molecule possesses a center of symmetry, comprising a Te center liganded in a trans manner by two bidentate N(SP(i)Pr(2))(SePPh(2)) groups. However, the (31)P, (77)Se, and (125)Te NMR spectra of [Te[N(SP(i)Pr(2))(SePPh(2))](2)] show two sets of resonances at 25 degrees C. The (31)P VT NMR spectra show two sets of resonances between -50 and +50 degrees C that coalesce between 80 and 100 degrees C, consistent with the presence of the cis as well as the trans isomer in solution.     

Ligand dependence of metal-metal bonding in the d(3)d(3) dimers M(2)X(9)(n-) (M(III) = Cr, Mo, W; M(IV) = Mn, Tc, Re; X = F, Cl, Br, I)

The ligand dependence of metal-metal bonding in the d(3)d(3) face-shared M(2)X(9)(n-) (M(III) = Cr, Mo, W; M(IV) = Mn, Tc, Re; X = F, Cl, Br, I) dimers has been investigated using density functional theory. In general, significant differences in metal-metal bonding are observed between the fluoride and chloride complexes involving the same metal ion, whereas less dramatic changes occur between the bromide and iodide complexes and minimal differences between the chloride and bromide complexes. For M = Mo, Tc, and Re, change in the halide from F to I results in weaker metal-metal bonding corresponding to a shift from either the triple metal-metal bonded to single bonded case or from the latter to a nonbonded structure. A fragment analysis performed on M(2)X(9)(3-) (M = Mo, W) allowed determination of the metal-metal and metal-bridge contributions to the total bonding energy in the dimer. As the halide changes from F to I, there is a systematic reduction in the total interaction energy of the fragments which can be traced to a progressive destabilization of the metal-bridge interaction because of weaker M-X(bridge) bonding as fluoride is replaced by its heavier congeners. In contrast, the metal-metal interaction remains essentially constant with change in the halide.     

Zwei Formen (A- und B-Typ) von Pr2Te[SiO4]

Two Types (A and B) of Pr₂Te[SiO₄] Two forms of praseodymium(III) telluride ortho-silicate (Pr₂Te[SiO₄]) are obtained as light green, transparent single crystals (A type: bricks, B type: needles, both unsensitive to hydrolysis) from a CsCl melt by reacting Pr, TeO₂ and SiO₂ in stoichiometric ratios (950 °C, 10 d) in evacuated silica tubes. A-Pr₂Te[SiO₄] crystallizes orthorhombically (Pbcm; a = 633.70(3), b = 724.42(4), c = 1125.13(8) pm; Z = 4) with alternatingly arranged monolayers {(Pr2)Te}⁺ and {(Pr1)[SiO₄]}^– parallel (001). Pr1 exhibits a coordination number of nine (6 O and 3 Te) while Pr2 has ten next neighbours (6 O and 4 Te), in which all the oxygen atoms are components of discrete ortho-silicate tetrahedra ([SiO₄]^4–), as also is the case in the B-type structure. The telluride anions show coordination numbers of seven (3 Pr1 and 4 Pr2). B-Pr₂Te[SiO₄] crystallizes monoclinically (P2₁/c; a = 989.90(7), b = 648.03(4), c = 870.68(6) pm, β = 94.307(8)°; Z = 4) with along [100] alternatingly sheethed double layers [{(Pr1)Te}₂]²⁺ and [{(Pr2)[SiO₄]}₂]^2–. This results in coordination numbers of eight (4 O and 4 Te) for Pr1, nine plus one (8 O and 1 + 1 Te) for Pr2, and five plus one (4 Pr1 and 1 + 1 Pr2) for Te. The almost 8% higher density of Pr₂Te[SiO₄] in the A-type structure (D_x = 6.45 g/cm³) compared to that of B-type Pr₂Te[SiO₄] (D_x = 5.98 g/cm³) is quite remarkable.     

Remarkable metal-rich ternary chalcogenides Sc14M3Te8 (M = Ru,Os)

In this novel motif, scandium atoms define infinite parallel chains of alternate trans-face-sharing cubes and pairs of square antiprisms in which each polyhedron is also centered by an M atom (M = Ru, Os). These chains are further linked into a three-dimensional structure by Sc(Te2Te4/2) octahedra. Physical property measurements show Sc14Ru3Te8 to be metallic and Pauli-paramagnetic, consistent with the results of extended Hückel band structure calculations. Matrix effects are evident in the dimensions within the chains. The major interactions are Sc-M and Sc-Te.     

STUDY ON ELECTRONIC STRUCTURE AND BONDING OF CLUSTER COMPOUND Sc_7Cl_(10)C_2

<正> The electronic structure and bonding of the cluster compound Sc7Cl10C2 have been studied by INDO method. In contract to the weak interaction between metal-metal in the compound Gd10Cl18C4, the bonding between metal atoms (Sc-Sc) in Sc7Cl10C2 is rather strong. The contribution of the orbitals 4s and 4p is larger than that of 3d to the Sc-Sc bond. In the cluster compound, besides Sc-Sc bonding, there are Sc -C and Sc -Cl bonds. The contribution of 3d is larger than that of 4s and 4p to the bond Sc-C. The contribution of 3d is slightly less than that of 4p and 4s to the bond Sc-Cl. Among the three kinds of bonds, the Sc-Cl bond is the weakest, the bond order of the Sc-Sc is close to that of the Sc-C.     

Synthesis, structure, and bonding of Lu7Z2Te2 (Z = Ni, Pd, Ru). Linking typical tricapped trigonal prisms in metal-rich compounds

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.     

Syntheses,structures, and characterization of new lead(II)-tellurium(IV)-oxide halides: Pb3Te2O6X2 and Pb3TeO4X2 (X = Cl or Br)

The syntheses, structures, and characterization of four new lead(II)-tellurium(IV)-oxide halides, Pb(3)Te(2)O(6)X(2) and Pb(3)TeO(4)X(2) (X = Cl or Br) are reported. The materials are synthesized by solid-state techniques, using Pb(3)O(2)Cl(2) or Pb(3)O(2)Br(2) and TeO(2) as reagents. The compounds have three-dimensional structural topologies consisting of lead-oxide halide polyhedra connected to tellurium oxide groups. In addition, the Pb(2+) and Te(4+) cations are in asymmetric coordination environments attributable to their stereoactive lone pair. We also demonstrate that Pb(3)Te(2)O(6)X(2) and Pb(2)TeO(4)X(2) can be interconverted reversibly through the loss or addition of TeO(2). X-ray data: Pb(3)Te(2)O(6)Cl(2), monoclinic, space group C2/m (No. 12), a = 16.4417(11) A, b = 5.6295(4) A, c = 10.8894(7) A, beta = 103.0130(10) degrees, Z = 4; Pb(3)Te(2)O(6)Br(2), monoclinic, space group C2/m (No. 12), a = 16.8911(8) A, b = 5.6804(2) A, c = 11.0418(5) A, beta = 104.253(2) degrees, Z = 4; Pb(3)TeO(4)Cl(2), orthorhombic, space group Bmmb (No. 63), a = 5.576(1) A, b = 5.559(1) A, c = 12.4929(6) A, Z = 4; Pb(3)TeO(4)Br(2), orthorhombic, space group Bmmb (No. 63), a = 5.6434(4) A, b = 5.6434(5) A, c = 12.9172(6) A, Z = 4.