Antiprismatic Coordination Research Articles

Complexes of ZrIV and HfIV with monolacunary Keggin-and Dawson-type anions

The reactions of the tetranuclear hydroxo complexes [M4(µ2-OH)8(H2O)16]8+ (M = Zr or Hf) with the lacunary Keggin-type ([α-PW11O39]7−) and Dawson-type ([α 2-P2W17O61]10−) phosphotungstates in aqueous solutions produce the sandwich polyoxometalate complexes [M(α-PW11O39)2]10− (M = Zr (1) or Hf (2)) and [M(α 2-P2W17O61)2]16− (M = Zr (3) and Hf (4)). The complexes were isolated and structurally characterized as salts with potassium and dimethylammonium cations. The zirconium and hafnium atoms have a square antiprismatic coordination environment (coordination number is 8). In all complexes, the mutual arrangement of the ligands corresponds to the syn isomer. Hafnium complexes 2 and 4 are the first structurally characterized polyoxometalate complexes of this metal. The structures of the resulting compounds were confirmed also by 31P NMR spectroscopy in solution.

Crystal structure of new intermetallic compound Mg 3Co 2Ga 7

The Mg 3Co 2Ga 7 compound was prepared by a reaction of the elemental components in arc furnace and subsequent annealing at 670 K. Its crystal structure was solved and refined from X-ray single crystal data. Mg 3Co 2Ga 7 is a new structure type: monoclinic space group C2/ c, a = 9.0873(9) Å, b = 9.4598(9) Å, c = 9.4361(9) Å, β = 93.605(8)°, V = 809.5(1) Å 3. The coordination around magnesium atoms consist of 13 and 14 atoms. The icosahedron and tetragonal antiprismatic coordination for the gallium and cobalt atoms was obtained. The structure belongs to class 9, according to the Krypyakevich classification scheme.

Syntheses of two new hybrid metal-organic polymers using flexible aliphatic dicarboxylates and pyrazine: Crystal structures and magnetic studies

The reaction of metal ions, flexible aliphatic dicarboxylates and pyrazine in aqueous solution afford two new metal-organic coordination polymers, {[Cu 2( μ 2- η 2-O 2C(CH 2) 2CO 2- η 2- μ 2) 2(H 2O) 2]·2H 2O} n ( 1) and [Eu 2( μ 2- η 2-O 2CCH 2CO 2- η 1- μ 1) 2( μ 2- η 2-O 2CCH 2CO 2- η 2- μ 2)(H 2O) 6] n ( 2). Polymer 1 contains the paddle-wheel cage dicopper(II) units, forming a one-dimensional (1D) double-stranded chain structure along the a-axis, in which the copper(II) atoms are bridged by the carboxylate groups of four succinates. The intradimer Cu–Cu distance is 2.613(2) Å; the interdimer Cu⋯Cu distance is 6.473 Å. To our knowledge, compound 1 represents the first example of a double-stranded chain structure containing dinuclear paddle-wheel type cage. In the three-dimensional (3D) compound 2, each central Eu(III) ion have a distorted monocapped square antiprism coordination geometry. The structure is built up from two types of polymeric chains with [EuO 6(H 2O) 3] n units as tethers, resulting in microporous framework. The magnetic behavior of 1 shows that the occurrence of a strong antiferromagnetic coupling between the copper(II) ions through the short bridges via the carboxyl groups can be obtained; the best fittings to the experimental magnetic susceptibilities gave −2 J=314 cm −1.

Syntheses and X‐Ray Crystal Structures of Zirconium(IV) and Hafnium(IV) Complexes Containing Monovacant Wells—Dawson and Keggin Polyoxotungstates.

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Syntheses and X-ray Crystal Structures of Zirconium(IV) and Hafnium(IV) Complexes Containing Monovacant Wells−Dawson and Keggin Polyoxotungstates

The syntheses and crystal structures of a series of zirconium(IV) and hafnium(IV) complexes with Dawson monovacant phosphotungstate [alpha2-P2W17O61](10-) and in situ-generated Keggin monovacant phosphotungstate [alpha-PW11O39](7-), which was obtained by a reaction of [alpha-PW12O40](3-) with Na2CO3, are described. K15H[Zr(alpha2-P2W17O61)2].25H2O (K-1), K16[Hf(alpha2-P2W17O61)2].19H2O (K-2), (Et2NH2)10[Zr(alpha-PW11O39)2].7H2O (Et2NH2-3), and (Et2NH2)10[Hf(alpha-PW11O39)2].2H2O (Et2NH2-4), being afforded by reactions in aqueous solutions of monolacunary Dawson and Keggin polyoxotungstates with ZrCl2O.8H2O and HfCl2O.8H2O followed by exchanging countercations, were obtained as analytically pure, homogeneous colorless crystals. Single-crystal X-ray structure analyses revealed that the Zr(IV) and Hf(IV) ions are in a square antiprismatic coordination environment with eight oxygen atoms, four of them being provided from each of the two monovacant polyanion ligands. Although the total molecular shapes and the 8-coordinate zirconium and hafnium centers of complexes 1-4 are identical, the bonding modes (bond lengths and bond angles) around the zirconium(IV) and hafnium(IV) centers were dependent on the monovacant structures of the polyanion ligands. Additionally, the characterization of complexes 1-4 was accomplished by elemental analysis, TG/DTA, FTIR, and solution (31P and 183W) NMR spectroscopy.

Ho11ClTe16O48: Ein extrem chlorarmes Chlorid‐Oxotellurat(IV) des dreiwertigen Holmiums

AbstractHo11ClTe16O48: An Extremly Chlorine‐Poor Chloride Oxotellurate(IV) of Trivalent HolmiumWhile attempting to synthesize Ho2Te3O9 by reacting Ho2O3 with TeO2 (800 °C, 12 d) chloride from the CsCl flux was incidently mobilized and as by‐product, Ho11ClTe16O48 (triclinic, ${\rm P}{\bar 1}$; a = 551.52(3), b = 1193.54(6), c = 1834.63(9) pm, α = 100.814(3), β = 95.443(3), γ = 100.175(3)°; Z = 1), the first example of this new composition in the field of lanthanoid(III) chloride oxotellurates(IV) has been obtained. The six crystallographically different Ho3+ cations experience a six‐, seven‐ and eightfold coordination through oxygen atoms (d(Ho3+−O2−) = 221 – 280 pm), leading to octahedral, triangle‐square polyhedral, capped trigonal prismatic and square antiprismatic coordination figures. Initially, the corresponding [HoOn] polyhedra convene to layers parallel to the (001) plane via edge and corner sharing which again combine to a [Ho11O48]63− network via other individual [(Ho6)O6] octahedra and [(Ho2)2O4/2O4/1] chains along [100], whose three‐dimensional characteristic is unique among the lanthanoid(III) oxotellurates(IV) known to date. The eight crystallographically independent Te4+ cations exhibit coordination numbers of 3 and 3+1 in relation to oxygen, except Te1 with 3+1 O2− plus 1 Cl− as anionic neighbours. Apart from isolated [TeO3]2− polyhedra (Ψ1 tetrahedra: d(Te4+−O2−) = 184 – 196 pm) only double and triple groupings occur even in considering secondary Te4+···O2− contacts (d′(Te4+···O2−) = 218 – 264 pm). As with HoCl[TeO3], the tellurium‐oxygen partial structure does not get beyond a “zero‐dimensional” expression. The Te4+ cations adjust so well while lining the empty cavities within the $^{3}_{\infty}\rm [Ho_{11}O_{48}]^{63-}$ network, that still only two Te4+‐decorated channel types (oval and round) remain unoccupied, offering space for the non‐bonding electron pairs (“lone pairs”). The Cl− anions reside in the bigger oval channels (d(Cl−−Te4+) = 286, 352 and 358 pm, 2 × each). In the default of binding Ho3+−Cl− contacts, the correct description of this new compound would thus be holmium(III) oxochlorotellurate(IV) Ho11[Te16O48Cl] according to Ho11[TeO3]2[Te2O6]2[Te3O9]2{Cl[Te2O6]2}. The presence of chloride was not only detected by the structure refinement on the basis of X‐ray diffraction data, but also even in such small quantities by elementary analysis with the electron‐beam microprobe.

Molecular Structures of Tris(dipivaloylmethanato) Complexes of the Lanthanide Metals, Ln(dpm)3, Studied by Gas Electron Diffraction and Density Functional Theory Calculations: A Comparison of the Ln−O Bond Distances and Enthalpies in Ln(dpm)3 Complexes and the Cubic Sesquioxides, Ln2O3

The molecular structures of tris(dipivaloylmethanato)neodymium(III), Nd(dpm)3, and tris(dipivaloylmethanato)ytterbium(III), Yb(dpm)3, have been determined by gas electron diffraction (GED) and structure optimizations through density functional theory (DFT) calculations. Both molecules were found to have D3 molecular symmetry. The most important structure parameters (r(a) structure) are as follows (GED/DFT): Nd-O = 2.322(5)/2.383 A, Yb-O = 2.208(5)/2.243 A, O-Nb-O = 72.1(3)/71.3 degrees , and O-Yb-O = 75.3(2)/75.8 degrees . The twist angles of the LnO6 coordination polyhedron, defined as zero for prismatic and 30 degrees for antiprismatic coordination, were theta = 19.1(3)/14.2 degrees for Nd and 20.4(2)/19.2 degrees for Yb. Structure optimizations of La(dpm)3, Gd(dpm)3 Er(dpm)3, and Lu(dpm)3 by DFT also yielded equilibrium structures of D3 symmetry with bond distances of La-O = 2.438 A, Gd-O = 2.322 A, Er-O = 2.267 A, and Lu-O = 2.232 A. The Ln-O bond distances in 12 Ln(dpm)3 complexes studied by GED decrease in a nearly linear manner with the increasing atomic number (Z) of the metal atom, as do the Ln-O bond distances in the cubic modifications of 14 sesquioxides, Ln2O3. The bond distances in the dpm complexes are, however, about 2% shorter. The mean Ln-O bond rupture enthalpies of the cubic sesquioxides calculated from thermodynamic data in the literature vary in an irregular manner with the atomic number; the La-O, Gd-O, Tb-O, and Lu-O bonds are nearly equally strong, and the remaining bonds are significantly weaker. The Ln-O bond rupture enthalpies previously reported for 11 Ln(dpm)3 complexes are on the average 13 kJ mol(-1) or about 5% smaller than in the sesquioxides, but they vary in a similar manner along the series: it is suggested that the pattern reflects variations in the absolute enthalpies of the gaseous Ln atoms.

The crystallized solvent could influence the lanthanide water bonding?

Two gadonilium DOTAM complexes [Gd(DOTAM)H 2O](CF 3SO 3) 3 · 3H 2O ( 1) and [Gd(DOTAM)H 2O](CF 3SO 3) 3 · 0.5H 2O · CH 3CN ( 2) have the structure of the M isomer, with coordination geometry around the Gd ion capped square antiprismatic (SA). They differ for the Gd–O water bond lengths of 2.396(6) and 2.474(7) Å in ( 2) where two independent molecules are present in the crystal cell. The factors influencing the Gd–O water bond distance, important for the water exchange rate in MRI experiments, have been correlated to the different network of hydrogen bonds involving the Gd coordinated water molecule. The X-ray structure of the parent compound [Pr(DOTAM)H 2O](CF 3SO 3) 3 · H 2O · CH 3CN ( 3) reveals an unexpected twisted square antiprismatic (TSA) coordination geometry characteristic of the m isomer.

A Novel Three-Dimensional Network Containing Pr(III) Ions and Tartrate: Synthesis, Spectroscopic, Thermal, Ab Initio X-ray Powder Structure Analyses, and Photoluminescence Properties

A new praseodymium tartrate [Pr(C4H4O6)(C4H5O6)(H2O)] has been synthesized under hydrothermal conditions and investigated by UV−Vis, FTIR, X-ray powder diffraction, thermal and photoluminescence analyses. The compound crystallizes in the orthorhombic system with a = 21.973(4), b = 7.587(1), c = 5.958(1) Å, space group P212121, and Z = 4. The crystal structure has been solved from laboratory X-ray powder diffraction data using a direct space global optimization technique and refined by the Rietveld method. The Pr atoms in the complex have 9-fold coordination with respect to the oxygens, with the metal center in a distorted monocapped square antiprism coordination. The molecular structure of the complex reveals 22-membered (Pr4C10O8) nanosized rectangular motifs assembled into helical chains, which are further linked via carboxylate groups of the tartrate ligands forming a novel three-dimensional polymeric framework. A X-ray powder pattern of the anhydrous praseodymium tartrate obtained by heating the title compound at 230 °C revealed a monoclinic unit cell with a = 10.964(3), b = 11.612(2), c = 10.456(4) Å, β = 108.96(2)°. The luminescence spectra of the hydrated Pr complex exhibit a signal at 645 nm due to a 3P0 → 3F2 transition.

Two Modifications of Y2Piv6(Hpiv)6 crystals: Synthesis and structures

Crystals of two modifications of yttrium pivalate solvate Y2Piv6(HPiv )6(HPiv = (CH3)3CCOOH) are synthesized and studied by single-crystal X-ray diffraction analysis. The 3α-modification crystallizes in the monoclinic system, a = 16.394(2) A, b = 11.948(4) A, c = 20.352(3) A, β = 108.73(3)°, Z = 4, space group P21/n, R 1 = 0.105. Crystals of the β-modifications are also monoclinic, a = 21.617(4) A, b = 36.559(4) A, c = 29.930(4) A, β = 104.40(2)°, Z = 12, space group P21/c, R 1 = 0.050. The molecular structures of crystals of the α-and β-modifications consist of the Y2(μ2-Piv)4(Piv)2(HPiv)6 dimers. The Y atoms with a distorted antiprismatic coordination surrounding of the O atoms (Y-O 2.23–2.53 A) are linked by four bridging bidentate pivalate anions and form the structural fragment shaped into a distorted lantern. Monodentate Hpiv molecules participate in the formation of intramolecular hydrogen bonds with Piv ligands. Crystal structures of the α-and β-modifications differ in packing of the Y2Piv6(HPiv)6 dimers and in centrosymmetric nature of the dimers in the structure of the α-modification.

Synthesis and characterisation of dimeric eight-coordinate lanthanide(iii) complexes of a macrocyclic tribenzylphosphinate ligand

The macrocyclic ligand 1,4,7,10-tetraazacyclododecane-1,4,7-triyl(methylenebenzyl-phosphinic acid) H3L3, has been prepared and its complexes with Eu, Gd and Tb(III) studied by NMR, relaxometry, luminescence and single crystal X-ray crystallography. In solution and in the crystal, the complexes have eight-coordinate metal centres with bridging phosphinate groups linking the two twisted square antiprismatic coordination polyhedra. A single stereoisomer crystallises from solution with an RRR and SSS configuration at the P centres in each sub-unit. The relaxivity of [GdL3]2 is low (1.9 mM-1 s-1, 298 K, 20 MHz), consistent with the absence of any proximate water molecules. The terbium dimer possesses a relatively long excited state lifetime (2.47 ms, 298 K).

Synthesis and structural characterization of lanthanide(iii) nitrate complexes of a tetraiminodiphenol macrocycle in the solid state and in solution

The lanthanide(III) complexes [Ln(LH2)(NO3)3] 1-11(La-Er), 15(Y) and [Ln(LH2)(NO3)2(H2O)](NO3) 12-14 (Tm-Lu) of the tetraiminodiphenolate macrocycle L2- have been prepared by the transmetallation reaction between [Pb(LH2)(NO3)2] and Ln(NO3)3.nH2O. In these compounds, the uncoordinated imino nitrogens are protonated and are hydrogen bonded to the phenolate oxygens. The X-ray crystal structures of the La (1), Ho (10) and Lu (14) compounds have been determined. Compounds 1 and 10, in which all the three nitrates are bound in bidentate fashion, are isostructural with distorted bicapped square antiprism geometry for the metal centre. In [Lu(LH2)(NO3)2(H2O)](NO3) 14, of the two metal bound nitrates one is bidentate and the other is unidentate, while the metal centre obtains a distorted square antiprism coordination environment. Proton NMR spectra of the paramagnetic lanthanide complexes have been studied in detail. Contributions of contact and pseudo-contact shifts to the lanthanide induced isotropic shifts (LIS) of the macrocycle protons have been separated and good agreement has been obtained between the calculated LIS values and the experimentally observed values. Analysis of the NMR data has led us to conclude that all the complexes in dimethyl sulfoxide solution attain similar configurations. The absorption and emission spectral characteristic of several compounds have been investigated. The complexes of samarium (5) and europium (6) on photoexcitation at 400 nm exhibit well-resolved luminescence spectra at 77 K both in the solid state and a methanol-ethanol (1 : 4) glassy matrix. For the terbium (8) and dysprosium (9) complexes, however, the observed luminescence peaks are less resolved and weak in intensity.

Synthesis and crystal structure of a 1D disulfoxide-lanthanide(III) complex {[La(L)2(DMF)4](ClO4)3} n [L = 1,6-bis(ethylsulfinyl)hexane

A new disulfoxide-La(III) complex {[La(L)2(DMF)4](ClO4)3} n (1) has been prepared by the reaction of La(ClO4)3 · nH2O and a flexible disulfoxide ligand, 1,6-bis(ethylsulfinyl)hexane (L), and characterized by elemental analysis, IR and single-crystal X-ray diffraction analysis (monoclinic system, space group C2/c, with a = 24.94(2), b = 12.012(8), c = 20.81(1) Å, β = 117.57(1)°, V = 5527(6) Å3 and Z = 4). The crystal structure consists of polymeric chains of {[La(L)2(DMF)4]3+} n cations and anions. In the cation of 1, each La(III) center is coordinated to eight O atoms from four distinct L ligands and four DMF molecules to give a square antiprism coordination geometry. The adjacent two La(III) ions are linked by two L ligands, which adopt bis-monodentate O-coordination bridging mode to form a double-bridging zigzag chain containing 22-membered macrocycles.

Poly[sesqui(μ4-biphenyl-4,4′-dicarboxylato-κ4O:O′:O′′:O′′′)(diethylformamide-κO)gadolinium

The crystal structure of the title compound, [Gd(C14H8O4)1.5(C5H11NO)]n, comprises chains of Gd atoms intra­connected by the carboxyl­ate groups of the biphenyl-4,4′-dicarboxyl­ate (BPDC) linkers, one of which is disposed about a twofold axis. The Gd atom chains are aligned along the b axis and are inter­connected by BPDC linkers, creating a three-dimensional framework. A single diethyl­formamide (DEF) mol­ecule is bonded to each Gd atom. This mol­ecule is positioned in the cavities formed by the inter­connection of the Gd atom chains via the BPDC linkers. Due to the steric constraints of the carboxyl­ate groups, the square antiprismatic coordination geometry of eight O atoms (one from the DEF mol­ecule and seven from carboxyl­ate groups) around Gd is distorted.

Synthesis and crystal structure of the pyrovanadate Na2ZnV2O7

The compound Na2ZnV2O7 with an åkermanite-type structure has been synthesized. It has a tetragonal unit cell, a=8.2711(4), c=5.1132(2) Å, and crystallizes with P-421m symmetry, Z=2. Its crystal structure has been refined from a combination of X-ray and neutron powder diffraction data. The structure contains layers of corner-sharing VO4 and ZnO4 tetrahedra, the former in pairs forming pyrovanadate V2O7 units. The sodium atoms are positioned between the layers, with a distorted antiprismatic coordination of oxygen atoms.

Catena-Poly[[[diaquacalcium(II)]-μ-oxydiacetato-[tetraaquamanganese(II)]-μ-oxydiacetato] dihydrate

In the title complex, {[CaMn(C4H4O5)2(H2O)6]·2H2O}n, the CaII and MnII ions are bridged by oxydiacetate (ODA) dianions to form zigzag polymeric chains. The CaII ion is located at a twofold axis and is coordinated by two tridentate ODA and two water mol­ecules with a distorted tetra­gonal antiprism coordination geometry. The MnII ion is located at another twofold axis, and assumes a distorted octa­hedral coordination geometry formed by four water mol­ecules and two carboxyl O atoms from monodentate ODA dianions also chelating to the neighboring CaII atoms.

Selten-Erd-Mandelate. Synthese und Kristallstrukturen von Pr(Man)3(ManH) und Er(Man)3(H2O)2 / Synthesis and Crystal Structures of Pr(Man)3(ManH) and Er(Man)3(H2O)2

Pr(Man)3(ManH) and Er(Man)3(H2O)2 (ManH = mandelic acid) have been synthesized by slow evaporation of aqueous solutions of rare-earth salts (Pr(OH)3, ErCl3 · 6H2O) with mandelic acid (α-hydroxy-phenyl acetic acid, C8H8O3) and their crystal structures were determined on the basis of X-ray data. In the crystal structure of Pr(Man)3(ManH) (1) (monoclinic, P21, a = 574.8(1), b = 3042.5(4), c = 908.4(1) pm, β = 92.09(2)°, Z = 2) the Pr(III) ions are surrounded by eight oxygen atoms in a distorted square antiprismatic fashion with distances Pr-O in the range 241 to 254 pm. These polyhedra are connected by coordinative bonds to chains paralleling the crystallographic [100] direction. In Er(Man)3(H2O)2 (2) (orthorhombic, P212121, a = 577.7(3), b = 1816.3(13), c = 2329.4(13) pm, Z = 4) the crystal structure contains isolated complexes with octa-coordinated erbium atoms chelated by three mandelate anions through one of their carboxylate oxygen atoms and the alcoholic hydroxyl group. Two water molecules complete the distorted square antiprismatic coordination sphere.

Pentaaqua(oxydiacetato-κ3O,O′,O′′)strontium(II) monohydrate

In the title compound, [Sr(C4H4O5)(H2O)5]·H2O, the SrII atom is coordinated by a tridentate oxydiacetate dianion (ODA) and five water mol­ecules, with a distorted square antiprism coordination geometry. The ODA chelates meridionally to the SrII atom with a planar structure. The Sr—O bond distances range from 2.505 (2) to 2.688 (2) Å.

Synthesis and Crystal Structure of KLa[C(CN)3]4·H2O containing a Shielded Potassium Ion

AbstractKLa[C(CN)3]4·H2O was crystallized from an aqueous solution containing La(NO3)3·6H2O and K[C(CN)3]. The crystal structure was solved and refined from X‐ray single crystal data (P4/n, Z = 2, a = b = 12.379(1) Å, c = 6.5695(8) Å, V = 1006.7(2) Å3). Solid KLa[C(CN)3]4·H2O forms a framework structure with bridging tricyanomethanide ions, each of them connecting two La3+ ions and one K+ ion. Potassium is apparently situated in a tetrahedral environment with four K–N distances of 2.741(3) Å, shielded by four other tricyanomethanide ions. Each La3+ has a square antiprismatic coordination of nitrogen atoms from eight [C(CN)3]– ions, and this antiprism is mono‐capped by one water molecule.

The Bivalent Metal Hypophosphites Sr(H2PO2)2, Pb(H2PO2)2 and Ba(H2PO2)2.

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