Fluorinated heterometallic ß-diketonates as volatile single-source precursors for the synthesis of low-valent mixed-metal fluorides.

Hexafluoroacetylacetonates that contain lead and divalent first-row transition metals, PbM(hfac)(4) (M = Ni (1), Co (2), Mn (3), Fe (4), and Zn (5)), have been synthesized. Their heterometallic structures are held together by strong Lewis acid-base interactions between metal atoms and diketonate ligands acting in chelating-bridging fashion. Compounds 1-5 are highly volatile and decompose below 350 °C. Fluorinated heterometallic ß-diketonates have been used for the first time as volatile single-source precursors for the preparation of mixed-metal fluorides. Complex fluorides of composition Pb(2)MF(6) have been obtained by decomposition of 1-5 in a two-zone furnace under low-pressure nitrogen flow. Lead-transition metal fluorides conform to orthorhombically distorted Aurivillius-type structure with layers of corner-sharing [MF(6)] octahedra separated by α-PbO-type (Pb(2)F(2)) blocks. Pb(2)NiF(6) and Pb(2)CoF(6) were found to exhibit magnetic ordering below 80 and 43 K, respectively. The ordering is antiferromagnetic, with a weak, uncompensated moment due to the canting of spins. The Pb(2)MF(6) fluorides represent a new class of prospective magnetoelectric materials combining transition metals and lone-pair main-group cations.

New class of single-source precursors for the synthesis of main group-transition metal oxides: heterobimetallic Pb-Mn beta-diketonates.

Heterometallic lead-manganese beta-diketonates have been isolated in pure form by several synthetic methods that include solid-state and solution techniques. Two compounds with different Pb/Mn ratios, PbMn(2)(hfac)(6) (1) and PbMn(hfac)(4) (2) (hfac = hexafluoroacetylacetonate), can be obtained in quantitative yield by using different starting materials. Single crystal X-ray investigation revealed that the solid-state structure of 1 contains trinuclear molecules in which lead metal center is sandwiched between two [Mn(hfac)(3)] units, while 2 consists of infinite chains of alternating [Pb(hfac)(2)] and [Mn(hfac)(2)] fragments. The heterometallic structures are held together by strong Lewis acid-base interactions between metal atoms and diketonate ligands acting in chelating-bridging fashion. Spectroscopic investigation confirmed the retention of heterometallic structures in solutions of non-coordinating solvents as well as upon sublimation-deposition procedure. Thermal decomposition of heterometallic diketonates has been systematically investigated in a wide range of temperatures and annealing times. For the first time, it has been shown that thermal decomposition of heterometallic diketonates results in mixed-metal oxides, while both the structure of precursors and the thermolysis conditions have a significant influence on the nature of the resulting oxides. Five different Pb-Mn oxides have been detected by X-ray powder diffraction when studying the decomposition of 1 and 2 in the temperature range 500-800 degrees C. The phase that has been previously reported as "Pb(0.43)MnO(2.18)" was synthesized in the pure form by decomposition of 1, and crystallographically characterized. The orthorhombic unit cell parameters of this oxide, obtained by electron diffraction technique, have been subsequently refined using X-ray powder diffraction data. Besides that, a previously unknown lead-manganese oxide has been obtained at low temperature decomposition and short annealing times. The parameters of its monoclinically distorted unit cell have been determined. The EDX analysis revealed that this compound has a Pb/Mn ratio close to 1:4 and contains no appreciable amount of fluorine.

Supramolecular assembly of heterocirculenes in 2D and 3D.

The results of a high-resolution ambient STM study of 'sulflower' (octathio[8]circulene) and 'selenosulflower' (sym-tetraselena-tetrathio[8]circulene) molecules, immobilized in a hydrogen-bonded matrix of trimesic acid (TMA) at the solid-liquid interface, are compared with the STM and X-ray structure of separate host and guest 2D and 3D crystals, respectively.

The high-pressure form of cadmium vanadate, CdV(2)O(6).

The crystal structure of a new high-pressure modification of cadmium divanadium hexaoxide, CdV(2)O(6), was refined from X-ray single-crystal data. It contains zigzag chains of edge-sharing VO(6) octahedra. Octahedra in adjacent chains share corners and form corrugated layers. Octahedrally coordinated Cd atoms, which lie on twofold axes, are situated between the layers. The columbite-like structure results in a strong distortion of the CdO(6) octahedra which may be stabilized only at high pressure.

Pb(2.63)Cd(2)V(3)O(12), a cation-deficient garnet-type vanadate.

In the crystal structure of the cation-deficient garnet Pb(2.63)Cd(2)V(3)O(12) (lead cadmium vanadium oxide), the Cd and V atoms fully occupy octahedral and tetrahedral sites, respectively, whereas the Pb atoms partially occupy a dodecahedral site. The total Pb and Cd content indicates that vanadium is slightly reduced from the +5 oxidation state.

The new lead vanadylphosphate Pb2VO(PO4)2.

The structure of dilead vanadium oxide bis(phosphate) contains corrugated layers formed by VO5 square pyramids oriented in opposite directions in a chessboard fashion. The pyramids are connected by tetrahedral PO4 groups. The layers are separated by the Pb atoms and isolated PO4 tetrahedra.

A new whitlockite, Ca8.42Na1.16V(PO4)7.

Single crystals of a new complex phosphate, calcium sodium vanadium phosphate, Ca8.42Na1.16V(PO4)7, have been grown from a melt under an inert atmosphere. The crystal structure has rhombohedral (R3c) symmetry and belongs to the whitlockite structure type. Vanadium(III) ions occupy nearly regular octahedral sites (M5 with 3 point symmetry), which share corners with six PO4 tetrahedra to form isolated units. The calcium ions occupy eight- and nine-coordinated sites. The sodium ions partially occupy one octahedral position and share one nine-coordinated position with a Ca atom.

Coordination polymers formed in solution and in solvent-free environment. Structural transformation due to interstitial solvent removal revealed by X-ray powder diffraction.

The crystal-to-powder transformation induced by solvent removal has been examined through a direct comparison of the structures of the solvated and the unsolvated coordination products determined by single crystal and powder X-ray diffraction, respectively.

Bulk material vs. single crystal: powder diffraction to the rescue.

The crystal structure of bulk microcrystalline material obtained by interaction of two rigid building blocks, namely dirhodium(ii) tetra(trifluoroacetate), [Rh2(O2CCF3)4], and bis(4'-pyridyl)diphenylsilane, (C6H5)2Si(C5H4N)2, has been solved ab initio using X-ray powder diffraction data. The title product of the 1 [ratio] 1 composition, [Rh2(O2CCF3)4.(mu2-(C6H5)2Si(C5H4N)2)], is a one-dimensional zigzag polymer built on axial Rh...N interactions averaged at 2.16 A. Its structural characterization complements the previously reported product of the 2:1 composition obtained from the same reaction, namely {[Rh2(O2CCF3)4]2.(mu4-(C6H5)2Si(C5H4N)2)}. The latter has a 2D layered network revealed by the single crystal diffraction study. A combination of powder and single crystal X-ray techniques is shown to be methodologically important and complementary for understanding of product assembling in the system.

Synthesis and crystal structure of lithium beryllium deuteride Li2BeD4.

Single-phase ternary deuteride Li(2)BeD(4) was synthesized by a high-pressure high-temperature technique from LiD and BeD(2). The crystal structure of Li(2)BeD(4) was solved from X-ray and neutron powder diffraction data. The compound crystallizes in the monoclinic space group P2(1)/c with lattice parameters a = 7.06228(9) A, b = 8.3378(1) A, c = 8.3465(1) A, beta =93.577(1) degrees, and Z = 8. Its structure contains isolated BeD(4) tetrahedra and Li atoms that are located in the structure interstices. Li(2)BeD(4) does not undergo any structural phase transitions at temperatures down to 8 K.

Powder diffraction study of a coordination polymer comprised of rigid building blocks: [Rh2(O2CCH3)4.mu2-Se2C5H8-Se,Se']infinity.

The crystal structure of a new hybrid product comprised of two rigid building blocks, namely dirhodium(II) tetraacetate, [Rh(2)(O(2)CCH(3))(4)] (1), and 2,6-diselenaspiro[3.3]heptane, Se(2)C(5)H(8) (2), has been solved ab initio using laboratory source X-ray powder diffraction (XRPD) data. The rigid body refinement approach has been applied to assist in finding an adequate model and to reduce the number of the refined parameters. Complex [Rh(2)(O(2)CCH(3))(4).mu(2)-Se(2)C(5)H(8)-Se,Se'] (3) conforms to the triclinic unit cell with lattice parameters of a = 8.1357(4), b = 8.7736(4), and c = 15.2183(8) A, alpha = 77.417(3), beta = 88.837(3), and gamma = 69.276(4) degrees, V = 989.66(8) A(3), and Z = 2. The centrosymmetric P space group was selected for calculations. The final values of the reduced wR(p), R(p), and chi(2) were calculated at 0.0579, 0.0433, and 5.95, respectively. The structure of 3 is a one-dimensional zigzag polymer built on axial Rh...Se interactions at 2.632(6) A. The 2,6-diselenaspiro[3.3]heptane ligand acts as a bidentate linker bridging dirhodium units via both selenium atoms. The geometrical parameters of individual groups for rigid body refinement have been obtained from X-ray powder data for dirhodium(II) tetraacetate (1) and from single-crystal X-ray diffraction for diselenium molecule 2. The crystal structures of 1 and 2 are reported here for the first time. For 1 indexing based on XRPD data has resulted in the triclinic unit cell P with lattice parameters of a = 8.3392(7), b = 5.2216(5), and c = 7.5264(6) A, alpha = 95.547(10), beta = 78.101(6), and gamma = 104.714(13) degrees, V = 309.51(5) A(3), and Z = 1. The final values were wR(p) = 0.0452, R(p) = 0.0340, and chi(2) = 1.99. The 1D polymeric motif built on axial Rh.O interactions of the centrosymmetric dirhodium units has been confirmed for the solid-state structure of 1. Compound 2,6-diselenaspiro[3.3]heptane (2) conforms to the monoclinic space group P2(1)/c with the unit cell parameters of a = 5.9123(4), b = 19.6400(13), and c = 5.8877(4) A, beta = 108.5500(10) degrees, V = 648.15(8) A(3), and Z = 4.