The coordination chemistry of pyrazole-derived ligands

Synthesis, Structure, and Reactions of Hydride, Borohydride, and Aluminohydride Compounds of the f-Elements.

A wide variety of metal borohydrides, MBH4, have been discovered and characterized during the past decade, revealing an extremely rich chemistry including fascinating structural flexibility and a wide range of compositions and physical properties. Metal borohydrides receive increasing interest within the energy storage field due to their extremely high hydrogen density and possible uses in batteries as solid state ion conductors. Recently, new types of physical properties have been explored in lanthanide-bearing borohydrides related to solid state phosphors and magnetic refrigeration. Two major classes of metal borohydride derivatives have also been discovered: anion-substituted compounds where the complex borohydride anion, BH4−, is replaced by another anion, i.e. a halide or amide ion; and metal borohydrides modified with neutral molecules, such as NH3, NH3BH3, N2H4, etc. Here, we review new synthetic strategies along with structural, physical and chemical properties for metal borohydrides, revealing a number of new trends correlating composition, structure, bonding and thermal properties. These new trends provide general knowledge and may contribute to the design and discovery of new metal borohydrides with tailored properties towards the rational design of novel functional materials. This review also demonstrates that there is still room for discovering new combinations of light elements including boron and hydrogen, leading to complex hydrides with extreme flexibility in composition, structure and properties.

Metal borohydrides and derivatives – synthesis, structure and properties

Chemistry of Tris(pentamethylcyclopentadienyl) f-Element Complexes, (C5Me5)3M

The organometallic chemistry of the lanthanide elements in low oxidation states

LBL-1 0490C, Preprint Submi BIS(PENTAMETHYLCYCLOPENTADIENYL) VATI : CRYSTAL STRUCTURE IUM(II)TETRAHYDROFURAN T, Don Tilley, Helen a Ruben, , Brock Spencer, David H. Templeton April 1 TWO-WEEK LOAN COPY is a Library Copy which may borrowed two weeks. For a personal copy, Tech. Info. Division, Ext. 6782. for the U.S. of under Contract

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Divalent lanthanide chemistry. Bis (pentamethylcyclopentadienyl) europium(II) and -ytterbium(II) derivatives: crystal structure of bis (pentamethylcyclopentadienyl) (tetrahydrofuran ytterbium(II) -hemitoluene at 176 K

Crystals of (C/sub 5/Me/sub 5/)/sub 2/Yb(C/sub 5/H/sub 5/N)/sub 2/ crystallize in the monoclinic system, P2/sub 1//c, with a = 16.092 (6) A, b = 9.883 (4) A, c = 17.872 (7) A, and ..beta.. = 98.46 (3)/sup 0/ at 21/sup 0/C. For Z = 4 the calculated density is 1.42 g cm/sup -3/. Two pentamethylcyclopentadienyl rings and the nitrogen atoms of the two pyridine molecules coordinate to the Yb atom in a distorted tetrahedral arrangement with approximate C/sub 2/ symmetry. The Yb-N distances average 2.56 A, the Yb-C distances average 2.74 A, and the Yb-Cp(centers) average 2.46 A. The C/sub 5/Me/sub 5/ rings are in a staggered configuration with respect to each other. The methyl groups of the C/sub 5/Me/sub 5/ rings are bent 0.13 to 0.31 A out of the planes of the C/sub 5/ rings away from the Yb atom. The 3278 data with F/sup 2/ > 3 sigma(F/sup 2/) refined by full-matrix least squares to an R factor of 0.031. 2 figures, 1 table.

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Crystal structure of bis(pentamethylcyclopentadienyl)bis(pyridine)ytterbium(II)

The structure of Np(BH/sub 4/)/sub 4/ was determined by single-crystal x-ray diffraction methods at 130 K. The crystals are tetragonal, space group P4/sub 2//nmc; a = 8.559 (9) A, c = 6.017 (9) A, Z = 2.R = 0.114 for 352 reflections (Mo K..cap alpha.. radiation). The four borohydride ions are disposed tetrahedrally about the Np with Np-B distances of 2.46 (3) A. The boron atoms are connected to the Np atom with triple hydrogen bridge bonds similar to the terminal borohydrides in uranium borohydride. Hydrogen atoms were observed in the Fourier maps and refined. This molecular structure is similar to that found for hafnium and zirconium borohydride, but the space group is different. The vapor pressure, 10 mmHg at 25/sup 0/C, was measured in the range of -5 to 25/sup 0/C using a Bourdon gauge.

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Volatility and molecular structure of neptunium(IV) borohydride

As part of a study of structures of uranium complexes the crystal structure of tris(urea)uranyl sulfate was determined by single-crystal x-ray diffraction methods. The uranyl ion is coordinated to oxygen atoms from the three urea molecules and from the sulfate ions in a pentagonal-bipyramid arrangement in which the pentagonal bipyramids are bridged by the sulfate ions to form an infinite chain. This result is in contrast to the structure of pentakis(urea)dioxouranium(VI) dinitrate in which the oxygen atoms of the five urea molecules are coordinated to the uranyl ion to form discrete complexes with the same pentagonal-bipyramidal geometry; the nitrate ions are not coordinated to the uranyl ion. 1 figure, 4 tables. (DP)

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Structure of tris(urea)dioxouranium(VI) sulfate, UO2(OC(NH2)2)3SO4

The present research was undertaken to confirm the oxidation state of the metal and the hydridic nature of the hydrogen in metal hydrides by obtaining electron paramagnetic resonance (EPR) parameters sensitive to the oxidation state of the metal and to the sign of the charge on the hydrogen for representative lanthanides (Er, Dy, and Gd) diluted in the nonmagnetic host materials YHx and LaHx. In addition, for hydride compositions near x = 2.0, the environment of the dopant metal ion should be cubic for the majority of the ions present, thus providing a convenient situation for determining the oxidation state and electronic ground state of the ion in question so as to distinguish between protonic and hydridic crystalline electric fields.

Brock Spencer

Papers

Divalent lanthanide chemistry. Bis (pentamethylcyclopentadienyl) europium(II) and -ytterbium(II) derivatives: crystal structure of bis (pentamethylcyclopentadienyl) (tetrahydrofuran ytterbium(II) -hemitoluene at 176 K

Crystal structure of bis(pentamethylcyclopentadienyl)bis(pyridine)ytterbium(II)

Volatility and molecular structure of neptunium(IV) borohydride

Structure of tris(urea)dioxouranium(VI) sulfate, UO2(OC(NH2)2)3SO4

Electron paramagnetic resonance spectra of erbium(III), dysprosium(III), and gadolinium(III) in yttrium and lanthanum hydrides