RE(AuAl2)nAl2(AuxSi1-x)2: a new homologous series of quaternary intermetallics grown from aluminum flux

The combination of early rare earth metals (La- to Gd and Yb), gold, and silicon in molten aluminum results in the formation of intermetallic compounds with four related structures, forming a new homologous series: RE[AuAl2]nAl2(AuxSi(1-x))2, with x approximately 0.5 for most of the compound and n = 0, 1, 2, and 3. Because of the highly reducing nature of the Al flux, rare earth oxides instead of metals can also be used in these reactions. These compounds grow as large plate-like crystals and have tetragonal structure types that can be viewed as intergrowths of the BaAl4 structure and antifluorite-type AuAl2 layers. REAuAl2Si materials form with the BaAl4 structure type in space group I4/mmm (cell parameters for the La analogue are a = 4.322(2) A, c = 10.750(4) A, and Z = 2). REAu2Al4Si forms in a new ordered superstructure of the KCu4S3 structure type, with space group P4/nmm and cell parameters of the La analogue of a = 6.0973(6) A, c = 8.206(1) A, and Z = 2. REAu3Al6Si forms in a new I4/mmm symmetry structure type with cell parameters of a = 4.2733(7) A, c = 22.582(5) A, and Z = 2 for RE = Eu. The end member of the series, REAu4Al8Si, forms in space group P4/mmm with cell parameters for the Yb analogue of a = 4.2294(4) A, c = 14.422(2) A, and Z = 1. New intergrowth structures containing two different kinds of AuAl2 layers were also observed. The magnetic behavior of all these compounds is derived from the RE ions. Comparison of the susceptibility data for the europium compounds indicates a switch from 3-D magnetic interactions to 2-D interactions as the size of the AuAl2 layer increases. The Yb ions in YbAu(2.91)Al(6)Si(1.09) and YbAu(3.86)Al(8)Si(1.14) are divalent at high temperatures.     

Crystal growth and structural characterization of the new ordered palladates LnKPdO3 (Ln = La, Pr, Nd, Sm-Gd) and the isostructural, partially cu-substituted palladate PrK(Cu0.14Pd0.86)O3

Single crystals of a new series of lanthanide-containing palladates, LnKPdO3 (Ln = La, Pr, Nd, Sm-Gd), and a partially copper-substituted palladate, PrK(Cu0.14Pd0.86)O3, were grown from potassium hydroxide fluxes. The compounds are all isostructural and crystallize in the C2/m space group with lattice parameters ranging from a = 13.4232(8) to 13.0212(2) A, b = 3.9840(2) to 3.9096(2) A, c = 7.4424(4) to 7.3209(9) A, and beta = 105.644(2) to 104.427(2) degrees . The crystal structure contains ordered slabs of LnO7- and KO7-capped trigonal prisms arranged in a complex network of face-, edge-, and vertex-shared polyhedra which, in turn, share edges with PdO4 square planes.     

SrAu4In4 and Sr4Au9In13: polar intermetallic structures with cations in augmented hexagonal prismatic environments

The title compounds were synthesized via high-temperature reactions of the elements in welded Ta tubes and characterized by single-crystal X-ray diffraction analyses and band structure calculations. SrAu(3.76(2))In(4.24) crystallizes in the YCo5In3 structure type with two of eight network sites occupied by mixtures of Au and In: Pnma, Z = 4, a = 13.946(7), b = 4.458(2), c = 12.921(6) A. Its phase breadth appears to be small. Sr4Au9In 13 exhibits a new structure type, P_6 m2, Z = 1, a = 12.701(2), c = 4.4350(9) A. The Sr atoms in both compounds center hexagonal prisms of nominally alternating In and Au atoms and also have nine augmenting (outer) Au + In atoms around their waists so as to define 21-vertex Sr@Au9M4In8 (M = Au/In) and Sr@Au9In12 polyhedra, respectively. The relatively larger Sr content in the second phase also leads to condensation of some of the ideal building units into trefoil-like cages with edge-shared six-member rings. One overall driving force for the formation of these structures can be viewed as the need for each Sr cation to have as many close neighbors as possible in the more anionic Au-In network. The results also depend on the cation size as well as on the flexibility of the anionic network and an efficient intercluster condensation mode as all clusters are shared. Band structure calculations (LMTO-ASA) emphasize the greater strengths (overlap populations) of the Au-In bonds and confirm expectations that both compounds are metallic.     

Intermetallic compounds with near Zintl phase behavior: RE2Zn3Ge6 (RE = La, Ce, Pr, Nd) grown from liquid indium

A series of compounds has been discovered while investigating reactions of rare earth, transition metals, and Ge in excess indium. These compounds, RE2Zn3Ge6 (RE = La, Ce, Pr, Nd), are isostructural, crystallizing in the orthorhombic space group Cmcm with lattice parameters a = 5.9691(9) angstroms, b = 24.987(4) angstroms, and c = 5.9575(9) angstroms for La2Zn3Ge6, a = 5.9503(5) angstroms, b = 24.761(2) angstroms, and c = 5.9477(5) angstroms for the Ce analogue, a =5.938(2) angstroms, b = 24.708(8) angstroms, and c = 5.936(2) angstroms for Pr2Zn3Ge6, and a = 5.9094(7) angstroms, b = 24.619(3) angstroms, and c = 5.9063(5) angstroms for the Nd analogue. The structure is composed of PbO-like ZnGe layers and ZnGe4 cage layers and is related to the Ce4Zn8Ge(11-x) structure type. The bonding in the system can be rationalized using the Zintl concept resulting in a material that is expected to be a valence precise semiconductor, although its behavior is more consistent with it being a semimetal, making it an intermediate case. The results of band structure calculations and magnetic measurements of these compounds are discussed.     

Rare-earth metal(III) oxide selenides M4O4Se[Se2] (M=La, Ce, Pr, Nd, Sm) with discrete diselenide units: crystal structures, magnetic frustration, and other properties

The rare-earth metal(III) oxide selenides of the formula La4O4Se[Se2], Ce4O4Se[Se2], Pr4O4Se[Se2], Nd4O4Se[Se2], and Sm4O4Se[Se2] were synthesized from a mixture of the elements with selenium dioxide as the oxygen source at 750 degrees C. Single crystal X-ray diffraction was used to determine their crystal structures. The isostructural compounds M4O4Se[Se2] (M=La, Ce, Pr, Nd, Sm) crystallize in the orthorhombic space group Amm2 with cell dimensions a=857.94(7), b=409.44(4), c=1316.49(8) pm for M=La; a=851.37(6), b=404.82(3), c=1296.83(9) pm for M=Ce; a=849.92(6), b=402.78(3), c=1292.57(9) pm for M=Pr; a=845.68(4), b=398.83(2), c=1282.45(7) pm for M=Nd; and a=840.08(5), b=394.04(3), c=1263.83(6) pm for M=Sm (Z=2). In their crystal structures, Se2- anions as well as [Se-Se]2- dumbbells interconnect {[M4O4]4+} infinity 2 layers. These layers are composed of three crystallographically different, distorted [OM4]10+ tetrahedra, which are linked via four common edges. The compounds exhibit strong Raman active modes at around 215 cm(-1), which can be assigned to the Se-Se stretching vibration. Optical band gaps for La4O4Se[Se2], Ce4O4Se[Se2], Pr4O4Se[Se2], Nd4O4Se[Se2], and Sm4O4Se[Se2] were derived from diffuse reflectance spectra. The energy values at which absorption takes place are typical for semiconducting materials. For the compounds M4O4Se[Se2] (M=La, Pr, Nd, Sm) the fundamental band gaps, caused by transitions from the valence band to the conduction band (VB-CB), lie around 1.9 eV, while for M=Ce an absorption edge occurs at around 1.7 eV, which can be assigned to f-d transitions of Ce3+. Magnetic susceptibility measurements of Ce4O4Se[Se2] and Nd4O4Se[Se2] show Curie-Weiss behavior above 150 K with derived experimental magnetic moments of 2.5 micro B/Ce and 3.7 micro B/Nd and Weiss constants of theta p=-64.9 K and theta p=-27.8 K for the cerium and neodymium compounds, respectively. Down to 1.8 K no long-range magnetic ordering could be detected. Thus, the large negative values for theta p indicate the presence of strong magnetic frustration within the compounds, which is due to the geometric arrangement of the magnetic sublattice in form of [OM4]10+ tetrahedra.     

(Fluoren-9-ylidene)methanedithiolato complexes of gold: synthesis, luminescence, and charge-transfer adducts

Piperidinium 9H-fluorene-9-carbodithioate and its 2,7-di-tert-butyl-substituted analogue [(pipH)(S(2)CCH(C(12)H(6)R(2)-2,7)), R = H (1a), t-Bu (1b)] and 2,7-bis(octyloxy)-9H-fluorene-9-carbodithioic acid [HS(2)CCH(C(12)H(6)(OC(8)H(17))(2)-2,7), 2] and its tautomer [2,7-bis(octyloxy)fluoren-9-ylidene]methanedithiol [(HS)(2)C=C(C(12)H(6)(OC(8)H(17))(2)-2,7), 3] were employed for the preparation of gold complexes with the (fluoren-9-ylidene)methanedithiolato ligand and its substituted analogues. The gold(I) compounds Q(2)[Au(2)(mu-kappa(2)-S,S-S(2)C=C(C(12)H(6)R(2)-2,7))(2)], where Q(+) = PPN(+) or Pr(4)N(+) for R = H (Q(2)4a) or Q(+) = Pr(4)N(+) for R = OC(8)H(17) [(Pr(4)N)(2)4c], were synthesized by reacting Q[AuCl(2)] with 1a or 2 (1:1) and excess piperidine or diethylamine. Complexes of the type [(Au(PR'3))(2)(mu-kappa(2)-S,S-S(2)C=C(C(12)H(6)R(2)-2,7))(2)] with R = H and R' = Me (5a), Et (5b), Ph (5c), and Cy (5d) or R = t-Bu and R' = Me (5e), Et (5f), Ph (5g), and Cy (5h) were obtained by reacting [AuCl(PR'(3))] with 1a,b (1:2) and piperidine. The reactions of 1a,b or 2 with Q[AuCl(4)] (2:1) and piperidine or diethylamine gave Q[Au(kappa(2)-S,S-S(2)C=C(C(12)H(6)R(2)-2,7))(2)] with Q(+) = PPN(+) for R = H [(PPN)6a], Q(+) = PPN(+) or Bu(4)N(+) for R = t-Bu (Q6b), and Q(+) = Bu(4)N(+) for R = OC(8)H(17) [(Bu(4)N)6c]. Complexes Q6a-c reacted with excess triflic acid to give [Au(kappa(2)-S,S-S(2)C=C(C(12)H(6)R(2)-2,7))(kappa(2)-S,S-S(2)CCH(C(12)H(6)R(2)-2,7))] [R = H (7a), t-Bu (7b), OC(8)H(17) (7c)]. By reaction of (Bu(4)N)6b with PhICl(2) (1:1) the complex Bu(4)N[AuCl(2)(kappa(2)-S,S-S(2)C=C(C(12)H(6)(t-Bu)(2)-2,7))] [(Bu(4)N)8b] was obtained. The dithioato complexes [Au(SC(S)CH(C(12)H(8)))(PCy(3))] (9) and [Au(n)(S(2)CCH(C(12)H(8)))(n)] (10) were obtained from the reactions of 1a with [AuCl(PCy(3))] or [AuCl(SMe(2))], respectively (1:1), in the absence of a base. Charge-transfer adducts of general composition Q[Au(kappa(2)-S,S-S(2)C=C(C(12)H(6)R(2)-2,7))(2)].1.5TCNQ.xCH(2)Cl(2) [Q(+) = PPN(+), R = H, x = 0 (11a); Q(+) = PPN(+), R = t-Bu, x = 2 (11b); Q(+) = Bu(4)N(+), R = OC(8)H(17), x = 0 (11c)] were obtained from Q6a-c and TCNQ (1:2). The crystal structures of 5c.THF, 5e.(2)/(3)CH(2)Cl(2), 5g.CH(2)Cl(2), (PPN)6a.2Me(2)CO, and 11b were solved by X-ray diffraction studies. All the gold(I) complexes here described are photoluminescent at 77 K, and their emissions can be generally ascribed to LMMCT (Q(2)4a,c, 5a-h, 10) or LMCT (9) excited states.     

Syntheses,structure, and photoluminescence properties of the 1-dimensional chain compounds [(TPA)(2)Au][Au(CN)(2)] and (TPA)AuCl (TPA = 1,3,5-triaza-7-phosphaadamantane)

The structures and temperature-dependent photoluminescence properties of the one-dimensional compounds [(TPA)(2)Au][Au(CN)(2)], 1, and (TPA)AuCl, 2, are reported. An extended linear chain with weak Au.Au interactions along the c-axis is evident in the structure of 1, and a helical chain with a pitch of 3.271 A is seen for 2. The intrachain Au...Au separation is 3.457(1) and 3.396(2) A in 1 and 2, respectively. As a result of this weak Au...Au interaction, the physical properties of these compounds are anisotropic. Scanning electron microscopy (SEM) studies indicate that single crystals of both compounds are noninsulating. Single crystals of 1 do not luminesce visibly, but grinding the crystals finely initiates a strong green emission under UV irradiation at room temperature. Further interesting optical properties include the dependence of the emission profile of the powder on the exciting wavelength and luminescence thermochromism. When excited at wavelengths < 360 nm, the powder exhibits a blue emission at 425 nm while excitation with longer wavelengths leads to a green emission near 500 nm. While the green emission dominates at ambient temperature, cooling to cryogenic temperatures leads to the dominance of the blue emission. Fibers of 2 are luminescent at 78 K with an emission band centered at 580 nm. Compound 1 crystallizes in the orthorhombic space group Cccm (No. 66), with Z = 2, a = 6.011(1) A, b = 23.877(6) A, c = 6.914(1) A, V = 992.3(3) A(3), and R = 0.0337. Compound 2 crystallizes in the trigonal space group R3 (No. 148), with Z = 18, a = 22.587(2) A, b = 22.587(2) A, c = 9.814(2) A, V = 4336 A(3), and R = 0.0283.     

Coordination of lanthanide triflates and perchlorates with N,N,N',N'-tetramethylsuccinamide

Compounds formed from the reaction of N,N,N',N'-tetramethylsuccinamide (TMSA) with trivalent lanthanide salts possessing the poorly coordinating counteranions triflate (CF3SO3-) and perchlorate (ClO4-) have been prepared and examined. Structural features of these Ln-TMSA compounds have been studied in the solid phase by thermogravimetric analysis, infrared spectroscopy, and, in selected cases, by single-crystal X-ray diffraction and in solution by infrared spectroscopy. Eight-coordinate compounds, [Ln(TMSA)4]3+, derived from coordination of four succinamide ligands to the metal ion could be formed with all lanthanides examined (Ln = La, Pr, Nd, Eu, Yb, Lu). Structural analyses by single-crystal X-ray diffraction were performed for the lanthanide triflate salts Ln(C8H16N2O2)4(CF3SO3)3: Ln = La, compound 1, monoclinic, P2(1)/n, a = 11.0952(2) A, b = 19.2672(2) A, c = 24.9759(3) A, beta = 90.637(1) degrees, Z = 4, Dcalcd = 1.586 g cm-3; Ln = Nd, compound 2, monoclinic, C2/c, a = 24.6586(10) A, b = 19.3078(7) A, c = 11.1429(4) A, beta = 90.450(1) degrees, Z = 4, Dcalcd = 1.603 g cm-3; Ln = Eu, compound 3, monoclinic, C2/c, a = 24.4934(2) A, b = 19.3702(1) A, c = 11.1542(1) A, beta = 90.229(1) degrees, Z = 4, Dcalcd = 1.617 g cm-3; Ln = Lu, compound 5, monoclinic, C2/c, a = 24.2435(4) A, b = 19.6141(2) A, c = 11.2635(1) A, beta = 90.049(1) degrees, Z = 4, Dcalcd = 1.626 g cm-3. X-ray analysis was also carried out for the perchlorate salt: Ln = Eu, compound 4, triclinic, P1, a = 10.9611(2) A, b = 14.6144(3) A, c = 15.7992(2) A, alpha = 106.594(1) degrees, beta = 91.538(1) degrees, gamma = 90.311(1) degrees, Z = 2, Dcalcd = 1.561 g cm-3. In the presence of significant amounts of water, 7-coordinate compounds with mixed aquo-TMSA cation structures [Ln(TMSA)3(H2O)]3+ (Ln = Yb) and [Ln(TMSA)2(H2O)3]3+ (Ln = La, Pr, Nd, Eu, Yb) have been isolated with structural determinations by single-crystal X-ray diffraction obtained for the following species: Yb(C8H16N2O2)3(H2O)(CF3SO3)3, compound 6, monoclinic, P2(1)/n, a = 8.9443(3) A, b = 11.1924(4) A, c = 44.2517(13) A, beta = 93.264(1) degrees, Z = 4, Dcalcd = 1.735 g cm-3; Yb(C8H16N2O2)3(H2O)(ClO4)3, compound 7, monoclinic, Cc, a = 19.2312(6) A, b = 11.1552(3) A, c = 19.8016(4) A, beta = 111.4260(1) degrees, Z = 4, Dcalcd = 1.690 g cm-3; Yb(C8H16N2O2)2(H2O)3(CF3SO3)3, compound 8, triclinic, P1, a = 8.6719(1) A, b = 12.2683(2) A, c = 19.8094(3) A, alpha = 75.815(1) degrees, beta = 86.805(1) degrees, gamma = 72.607(1) degrees, Z = 2, Dcalcd = 1.736 g cm-3. Unlike in the analogous nitrate salts, only bidentate binding of the succinamide ligand to the lanthanide metal is observed. IR spectroscopy studies in anhydrous acetonitrile suggest that the solid-state structures of these Ln-TMSA compounds are maintained in solution.     

Ca4Au10In3: synthesis, structure, and bonding analysis. The chemical and electronic transformations from the isotypic Zr7Ni10 intermetallic

The title compound, Ca(4)Au(10)In(3) (e/a = 1.59), was synthesized by conventional high-temperature solid-state reactions and structurally analyzed by single-crystal X-ray diffraction: space group Cmca, a = 13.729(4) A, b = 10.050(3) A, c = 10.160(3) A, Z = 4. The structure, isotypic with that of Zr(7)Ni(10), features a novel three-dimensional [Au(10)In(3)] polyanionic framework built from sinusoidal Au layers that are interconnected by significant Au-Au and Au-In interactions. A prominent electronic feature is the presence of a pseudogap and empty bonding states above the Fermi level according to LMTO calculations, reminiscent of the tunable electronic properties discovered for Mg(2)Zn(11)-type phases. The natures of the chemical and electronic redistributions from Zr(7)Ni(10) to Ca(4)Au(10)In(3) are considered. The Au backbone appears to be particularly important.     

The synthesis and characterization of compounds of the type Hg[1-C(6)H(4)-2-C(H)=NC(6)H(5-n)R(n)](2)

The organomercurial compounds Hg[1-C(6)H(4)-2-C(H)=NC(6)H(5-n)R(n)](2) (R = 4-NMe(2), 6a; 4-Me, 6b; 4-I, 6c; 4-NO(2), 6d; 2-(i)Pr, 6e; 2-Me, 6f; 2,6-(i)Pr(2), 6g; 2,6-Me(2), 6h) have been prepared in good overall yield from 2-bromobenzaldehyde. All of the compounds have been characterized by elemental analysis, (1)H NMR, (13)C[(1)H] NMR, and infrared spectroscopy. In addition, compounds 6a [C(30)H(30)HgN(4), triclinic, P, a = 6.20000(10) A, b = 9.2315(2) A, c = 10.9069(3) A, alpha = 85.8510(10) degrees, beta = 89.3570(10) degrees, gamma = 87.206(2) degrees, Z = 1], 6b [C(28)H(24)HgN(2), monoclinic, P2(1)/c, a = 12.8260(5) A, b = 14.0675(4) A, c = 6.1032(2) A, beta = 90.0990(10) degrees, Z = 2], 6g [C(38)H(44)HgN(2), triclinic, P, a = 8.2626(2) A, b = 9.8317(2) A, c = 11.8873(3) A, alpha = 103.6650(10) degrees, beta = 109.3350(10) degrees, gamma = 104.627(2) degrees, Z = 1], and 6h [C(30)H(28)HgN(2), monoclinic, P2(1)/c, a = 12.5307(2) A, b = 10.9852(2) A, c = 18.2112(2) A, beta = 104.0190(10) degrees, gamma = 87.206(2) degrees, Z = 4] have been characterized by low-temperature single-crystal X-ray diffraction studies, and two different molecular geometries about the central mercury atom have been observed; intramolecular contacts suggest a van der Waals radius for Hg of 2.1-2.2 A.     

Three alkali-metal-gold-gallium systems. Ternary tunnel structures and some problems with poorly ordered cations

Six new intermetallic compounds have been characterized in the alkali metal (A = Na, Rb, Cs)-gold-gallium systems. Three isostructural compounds with the general composition A(0.55)Au(2)Ga(2), two others of AAu(3)Ga(2) (A = Rb, Cs), and the related Na(13)Au(41.2)Ga(30.3) were synthesized via typical high-temperature reactions and their crystal structures determined by single-crystal X-ray diffraction analysis: Na(0.56(9))Au(2)Ga(2) (I, I4/mcm, a = 8.718(1) ?, c = 4.857(1) ?, Z = 4), Rb(0.56(1))Au(2)Ga(2) (II, I4/mcm, a = 8.950(1) ?, c = 4.829(1) ?, Z = 4), Cs(0.54(2))Au(2)Ga(2) (III, I4/mcm, a = 9.077(1) ?, c = 4.815(1) ?, Z = 4), RbAu(3)Ga(2) (IV, Pnma, a = 13.384(3) ?, b = 5.577(1) ?, c = 7.017(1) ?, Z = 4), CsAu(3)Ga(2) (V, Pnma, a = 13.511(3) ?, b = 5.614(2) ?, c = 7.146(1) ?, Z = 4), Na(13)Au(41.2(1))Ga(30.3(1)) (VI, P6 mmm, a = 19.550(3) ?, c = 8.990(2) ?, Z = 2). The first three compounds (I-III) are isostructural with tetragonal K(0.55)Au(2)Ga(2) and likewise contain planar eight-member Au/Ga rings that stack along c to generate tunnels and that contain varying degrees of disordered Na-Cs cations. The cation dispositions are much more clearly and reasonably defined by electron density mapping than through least-squares refinements with conventional anisotropic ellipsoids. Orthorhombic AAu(3)Ga(2) (IV, V) are ordered ternary Rb and Cs derivatives of the SrZn(5) type structure, demonstrating structural variability within the AAu(3)Ga(2) family. All attempts to prepare an isotypic "NaAu(3)Ga(2)" were not successful, but yielded only a similar composition Na(13)Au(41.2)Ga(30.3) (NaAu(3.17)Ga(2.33)) (VI) in a very different structure with two types of cation sites. Crystal orbital Hamilton population (COHP) analysis obtained from tight-binding electronic structure calculations for idealized I-IV via linear muffin-tin-orbital (LMTO) methods emphasized the major contributions of heteroatomic Au-Ga bonding to the structural stability of these compounds. The relative minima (pseudogaps) in the DOS curves for IV correspond well with the valence electron counts of known representatives of this structure type and, thereby, reveal some magic numbers to guide the search for new isotypic compounds. Theoretical calculation of total energies vs volumes obtained by VASP (Vienna Ab initio Simulation Package) calculations for KAu(3)Ga(2) and RbAu(3)Ga(2) suggest a possible transformation from SrZn(5)- to BaZn(5)-types at high pressure.     

In search of cyclohexane-like Sn6(12-): synthesis of Li2Ln5Sn7 (Ln = Ce, Pr, Sm, Eu) with an open-chain heptane-like Sn7(16-) instead

The title compounds were prepared by direct reactions of the corresponding elements at high temperature. They are isostructural and crystallize in the chiral orthorhombic space group P212121 (Li2Ce5Sn7: a = 6.273(1), b = 13.839(2), and c = 17.467(2) A; Li2Pr5Sn7: a = 6.241(1), b = 13.762(2), and c = 17.367(1) A; Li2Sm5Sn7: a = 6.262 (1), b = 13.809(1), and c = 17.432(1) A; Li2Eu5Sn7: a = 6.165(1), b = 13.562(2), and c = 17.128(1) A). The structure contains isolated Sn7 oligomers that resemble the carbon core of an open-chain heptane molecule C7H16. Although these heptamers are stacked along the a axis at a distance that is comparable to the distances within the heptamer, electronic structure calculations show that this intermolecular contact is nonbonding for a formal charge of 16- or higher per heptamer. A hypothetical lower charge of 14-, on the other hand, leads to positive and substantial bond-overlap population that would result in branched infinite chains of infinity[Sn714-]. Magnetic measurements of the Ce and Pr compounds indicate a 3+ oxidation state for the rare-earth cations and, therefore, 17 available electrons from the cations per formula unit. According to four-probe conductivity measurements, the compounds are metallic.     

Indium flux synthesis of RE4Ni2InGe4 (RE = Dy, Ho, Er, and Tm): an ordered quaternary variation on the binary phase Mg5Si6

The quaternary compounds RE4Ni2InGe4 (RE = Dy, Ho, Er, and Tm) were obtained as large single crystals in high yields from reactions run in liquid In. The title compounds crystallize in the monoclinic C2/m space group with the Mg(5)Si(6) structure type with lattice parameters a = 15.420(2) A, b = 4.2224(7) A, c = 7.0191(11) A, and beta = 108.589(2) degrees for Dy4Ni2InGe4, a = 15.373(4) A, b = 4.2101(9) A, c = 6.9935(15) A, and beta = 108.600(3) degrees for Ho4Ni2InGe4, a = 15.334(7) A, b = 4.1937(19) A, c = 6.975(3) A, and beta =108.472(7) degrees for Er4Ni2InGe4, and a = 15.253(2) A, b = 4.1747(6) A, c = 6.9460(9) A, and beta = 108.535(2) degrees for Tm4Ni2InGe4. RE4Ni2InGe4 formed in liquid In from a melt that was rich in the rare-earth component. These compounds are polar intermetallic phases with a cationic rare-earth substructure embedded in a transition metal and main group matrix. The rare-earth atoms form a highly condensed network, leading to interatomic distances that are similar to those found in the elemental lanthanides themselves. The Dy and Ho analogues display two maxima in the susceptibility, suggesting antiferromagnetic ordering behavior and an accompanying spin reorientation. The Er analogue shows only one maximum in the susceptibility, and no magnetic ordering was observed for the Tm compound down to 2 K.     

Synthesis, structure, and bonding of BaAuTl3 and BaAuIn3: stabilization of BaAl4-type examples of the heavier triels through gold substitution

The title compounds have been synthesized by high temperature means and characterized by X-ray structural analysis, physical property measurements, and electronic structure calculations. The compounds crystallize in the three-dimensional tetragonal structure of BaAl(4), I4/mmm, Z = 2 (a = 4.8107(4), 4.8604(2) A, and c = 11.980(2), 12.180(2) A for BaAuIn(3) and BaAuTl(3), respectively). Gold randomly substitutes for 50% of the In or Tl in the apical (4e) positions in the network, generating apical-apical atom distances of 2.77 and 2.70 A, respectively, values that are comparable to the single bond metallic radii sum for Au plus In, and 0.08 A less than that for Au plus Tl. Relativistic effects appear to be important for both of the latter elements. The shrinkage in distances and increase in bond strengths evidently stabilize BaAuTl(3) relative to the distorted BaTl(4) with a presumably oversized triel lattice. EHTB band calculations indicate that the two compounds are electron-deficient relative to optimal Au-Tr and Au-Au bonding and metallic, the latter in agreement with measured properties of BaAuTl(3).     

Synthesis and characterization of novel homoleptic N,N-dialkylcarbamato complexes of antimony: precursors for the deposition of antimony oxides

A series of tris(N,N-dialkylcarbamato)antimony(III) complexes, Sb(O(2)CNR(2))(3) (R = Me, Et, Pr(i)()), have been synthesized and are the first members of this class of compound to have been crystallographically characterized. Sb(O(2)CNMe(2))(3) (1) exists as a weakly bound dimer, whereas its diethyl and diisopropyl analogues (2, 3) are monomeric. In addition, tetrakis(N,N-diethylcarbamato)tin(IV) (4) has been prepared for comparison and shown by single-crystal X-ray analysis to exhibit the relatively rare SnO(8) coordination. Crystallographic data: for 1, a = 8.7520(5) A, b = 14.2970(8) A, c = 11.8150(7) A, beta = 108.029(2) degrees, monoclinic, P2(1)/c, Z = 4; for 2, a = b = 14.4690(2) A, c = 16.6740(2) A, trigonal, Rthremacr;, Z = 6; for 3, a = 11.9881(2) A, b = 11.6521(3) A, c = 19.8780(6) A, beta = 90.401(1) degrees, monoclinic, P2(1)/n, Z = 4; for 4, a = 13.9654(2) A, b = 12.0817(2) A, c = 16.6752(2) A, beta = 108.1960(7) degrees, monoclinic, C2/c, Z = 4. Sb(O(2)CNMe(2))(3) has been used as a single-source precursor in the low-pressure chemical vapor deposition of the senarmonite form of Sb(2)O(3).     

New intermetallics YbAu2In4 and Yb2Au3In5

The intermetallic compounds YbAu(2)In(4) and Yb(2)Au(3)In(5) were obtained as single crystals in high yield from reactions run in liquid indium. Single crystal X-ray diffraction data of YbAu(2)In(4) showed that it crystallizes as a new structure type in the monoclinic space group P2(1)/m and lattice constants a = 7.6536(19) ?, b = 4.5424(11) ?, c = 9.591(2) ? and β = 107.838(4)°. The YbAu(2)In(4) compound is composed of a complex [Au(2)In(4)](3-) polyanionic network in which the rare-earth ions are embedded. Yb(2)Au(3)In(5) crystallizes in the polar space group Cmc2(1) with the Y(2)Rh(3)Sn(5) type structure and lattice constants a = 4.5351(9) ?, b = 26.824(5) ?, and c = 7.4641(15) ?. The gold and indium atoms define a complex three-dimensional [Au(3)In(5)] network with a broad range of Au-In (2.751(2) ?-3.0518(16) ?) and In-In (3.062(3) ?-3.3024(19) ?) distances. Magnetic susceptibility measurements of YbAu(2)In(4) revealed a transition at 25 K. Below the transition, the susceptibility of YbAu(2)In(4) follows Curie-Weiss behavior with an effective paramagnetic moment of 0.79 μ(B)/Yb. Magnetic susceptibility measurements on Yb(2)Au(3)In(5) show a mixed valent ytterbium and the magnetic moment within the linear region (<100 K) of 1.95 μ(B)/Yb. Heat capacity data for YbAu(2)In(4) and Yb(2)Au(3)In(5) give Debye temperatures of 185 and 153 K, respectively.     

Synthesis, structure, and reactions of binuclear gold(I) complexes containing two different bridging ligands

The binuclear cycloaurated compounds [Au(2)(mu-C(6)H(3)-2-PPh(2)-n-Me)(2)] (n = 5, 1a; n = 6, 1b) react with the digold(I) complexes [Au(2)(mu-S(2)CN(n)()Bu(2))(2)] and [Au(2)(mu-dppm)(2)](PF(6))(2) to give heterobridged dinuclear complexes [Au(2)(mu-C(6)H(3)-2-PPh(2)-n-Me)(mu-S(2)CN(n)Bu(2))] (n = 5, 5a; n = 6, 5b) and [Au(2)(mu-C(6)H(3)-2-PPh(2)-n-Me)(mu-dppm)]PF(6), (n = 5, 9a; n = 6, 9b), respectively. Complex 5a exists in the solid state as an infinite zigzag chain of dimeric units with intramolecular Au-Au separations of 2.8331(3) and 2.8243(3) A for independent molecules and intermolecular Au-Au separations of 3.0653(3) and 3.1304(3) A. Both 5a and 5b undergo oxidative addition with halogens to give the heterovalent, gold(I)-gold(III) compounds [XAu(I)(mu-2-Ph(2)PC(6)H(3)-n-Me)Au(III)X(eta(2)-S(2)CN(n)Bu(2))] [n = 5, X = Cl (6a), I (8a); n = 6, X = Cl (6b), Br (7b), I (8b)]. Compound 8a has been shown by X-ray crystallography to contain a gold(III) atom coordinated in a planar array by bidentate, chelating di-n-butyldithiocarbamate, iodide, and the sigma-aryl carbon atom, together with a gold(I) atom that is linearly coordinated by the phosphorus atom of the arylphosphine and by iodide. The intramolecular gold-gold distance of 3.2201(3) A indicates little or no interaction between the metal atoms. In contrast to the behavior of the homobridged complexes 1a and 1b, the heterobridged dithiocarbamate complexes 5a and 5b give structurally similar products on reaction with halogens, irrespective of the position of the ring methyl substituent. Crystal data for [Au(2)(mu-C(6)H(3)-2-PPh(2)-5-Me)(mu-S(2)CN(n)Bu(2))] (5a): triclinic, space group P1 (No. 2), with a = 11.3398(1), b = 15.9750(2), c = 16.4400(3) A, alpha = 91.0735(9), beta = 109.3130(7), gamma = 90.7666(8) degrees, V = 2809.47(6) A(3), and Z = 4. Crystal data for [IAu(I)(mu-2-Ph(2)PC(6)H(3)-5-Me)Au(III)I(eta(2)- S(2)CN(n)Bu(2))] (8a): triclinic, space group P1 (No. 2), with a = 8.6136(2), b = 9.3273, c = 21.1518(4) A, alpha = 84.008(1), beta = 84.945(1), gamma = 75.181(1) degrees, V = 1630.54(6) A(3), and Z = 2.     

Structural, dynamic, and theoretical studies of [AunPt2(PPh3)4(mu-S)2-n(mu 3-S)nL][PF6]n [n = 1, L = PPh3; n = 2, L = Ph2PCH2PPh2, (C5H4PPh2)2Fe

Three heterometallic Au-Pt complexes [Pt2(PPh3)4(mu-S)(mu 3-S)Au(PPh3)][PF6] (2), [Pt2(PPh3)4(mu 3-S)2Au2(mu-dppm)]-[PF6]2 (3), and [Pt2(PPh3)4(mu 3-S)2Au2(mu-dppf)][PF6]2 (4) have been synthesized from Pt2(PPh3)4(mu-S)2 (1) [dppm = Ph2PCH2PPh2; dppf = (C5H4PPh2)2Fe] and characterized by single-crystal X-ray crystallography. In 2, the Au(I) atom is anchored on only one of the sulfur centers. In 3 and 4, both sulfur atoms are aurated, showing the ability of 1 to support an overhead bridge structure, viz. [Au2(P-P)], with or without the presence of Au-Au bond. The change of dppf to dppm facilitates such active interactions. Two stereoisomers of complex 3 (3a,b) have been obtained and characterized by single-crystal X-ray crystallography. NLDFT calculations on 2 show that the linear coordination mode is stabilized with respect to the trigonal planar mode by 14.0 kJ/mol. All complexes (2-4) are fluxional in solution with different mechanisms. In 2, the [Au(PPh3)] fragment switches rapidly between the two sulfur sites. Our hybrid MM-NLDFT calculations found a transition state in which the Au(I) bears an irregular trigonal planar geometry (delta G++ = 19.9 kJ/mol), as well as an intermediate in which Au(I) adopts a regular trigonal planar geometry. Complexes 3a,b are roughly diastereoisomeric and related by sigma (mirror plane) conversion. This symmetry operation can be broken down to two mutually dependent fluxional processes: (i) rapid flipping of the dppm methylene group across the molecular plane defined by the overhead bridge; (ii) rocking motion of the two Au atoms across the S...S axis of the (Pt2S2) core. Modeling of the former by molecular mechanics yields a steric barrier of 29.0 kJ/mol, close to that obtained from variable-temperature 31P(1Hz) NMR study (33.7 kJ/mol). In 4, the twisting of the ferrocenyl moiety across the S...S axis is in concert with a rocking motion of the two gold atoms. The movement of dppf is sterically most demanding, and hence, 4 is the only complex that shows a static structure at lower temperatures. Pertinent crystallographic data: (2) space group P1, a = 15.0340(5) A, b = 15.5009(5) A, c = 21.9604(7) A, alpha = 74.805(1) degrees, beta = 85.733(1) degrees, gamma = 78.553(1) degrees, R = 0.0500; (3a) space group Pna2(1), a = 32.0538(4) A, b = 16.0822(3) A, c = 18.9388(3) A, R = 0.0347; (3b) space group Pna2(1), a = 31.950(2) A, b = 16.0157(8) A, c = 18.8460(9) A, R = 0.0478; (4) space group P2(1)/c, a = 13.8668(2) A, b = 51.7754(4) A, c = 15.9660(2) A, beta = 113.786(1) degrees, R = 0.0649.     

Four polyanionic compounds in the K–Au–Ga system: a case study in exploratory synthesis and of the art of structural analysis

The K-Au-Ga system has been investigated at 350 °C for <50 at. % K. The potassium gold gallides K(0.55)Au(2)Ga(2), KAu(3)Ga(2), KAu(2)Ga(4) and the solid solution KAu(x)Ga(3-x) (x = 0-0.33) were synthesized directly from the elements via typical high-temperature reactions, and their crystal structures were determined by single crystal X-ray diffraction: K(0.55)Au(2)Ga(2) (I, I4/mcm, a = 8.860(3) ?, c = 4.834(2) ?, Z = 4), KAu(3)Ga(2) (II, Cmcm, a = 11.078(2) ?, b = 8.486(2) ?, c = 5.569(1) ?, Z = 4), KAu(2)Ga(4) (III, Immm, a = 4.4070(9) ?, b = 7.339(1) ?, c = 8.664(2) ?, Z = 2), KAu(0.33)Ga(2.67) (IV, I-4m2, a = 6.0900(9) ?, c = 15.450(3) ?, Z = 6). The first two compounds contain different kinds of tunnels built of puckered six- (II) or eight-membered (I) ordered Au/Ga rings with completely different cation placements: uniaxial in I and III but in novel 2D-zigzag chains in II. III contains only infinite chains of a potassium-centered 20-vertex polyhedron (K@Au(8)Ga(12)) built of ordered 6-8-6 planar Au/Ga rings. The main structural feature of IV is dodecahedral (Au/Ga)(8) clusters. Tight-binding electronic structure calculations by linear muffin-tin-orbital methods were performed for idealized models of I, II, and III to gain insights into their structure-bonding relationships. Density of states curves reveal metallic character for all compounds, and the overall crystal orbital Hamilton populations are dominated by polar covalent Au-Ga bonds. The relativistic effects of gold lead to formation of bonds of greater population with most post-transition elements or to itself, and these appear to be responsible for a variety of compounds, as in the K-Au-Ga system.     

Structures and physical properties of rare-earth zinc antimonides Pr6Zn(1+x)Sb(14+y) and RE6Zn(1+x)Sb14 (RE = Sm, Gd-Ho)

A new series of isostructural ternary rare-earth zinc antimonides RE(6)Zn(1+x)Sb(14+y) (RE = Pr, Sm, Gd-Ho) has been obtained by direct reaction of the elements at 1050-1100 degrees C. Single-crystal X-ray diffraction studies revealed that these compounds adopt an orthorhombic structure type (space group Immm (no. 71), Z = 2, a = 4.28-4.11 A, b = 15.15-14.73 A, c = 19.13-18.56 A in the progression from RE = Pr to Ho) that may be regarded as stuffed variants of a (U(0.5)Ho(0.5))(3)Sb(7)-type host structure. Columns of face-sharing RE(6) trigonal prisms, centered by Sb atoms, occupy channels defined by an extensive polyanionic Sb network. This network is constructed from three-atom-wide and four-atom-wide Sb strips, the latter being linked together by single Sb atoms in RE(6)Zn(1+x)Sb(14) (RE = Sm, Gd-Ho; y = 0), but also by additional Sb-Sb pairs in a disordered fashion in Pr(6)Zn(1+x)Sb(14+y) (y = approximately 0.6). Interstitial Zn atoms then partially fill tetrahedral sites (occupancy of 0.5-0.7) and, to a lesser extent, square pyramidal sites (occupancy of 0.04-0.12), accounting for the observed nonstoichiometry with variable x. Except for the Gd member, these compounds undergo antiferromagnetic ordering below T(N) < 9 K, with the magnetic susceptibilities of the Tb, Dy, and Ho members following the Curie-Weiss law above T(N). For the Ho member, the thermal conductivities are low and the Seebeck coefficients are small and positive, implying p-type character consistent with the occurrence of partial Zn occupancies. At low temperatures (down to 5 K), electrical resistivity measurements for the Tb, Dy, and Ho members indicated metallic behavior, which persists at high temperatures (up to 560 K) for the Ho member. Band structure calculations on an idealized "Gd(6)Zn(2)Sb(14)" model revealed the existence of a pseudogap near the Fermi level.