Claude Belin

The intermetallic phases of gallium and alkali metals. Interpretation of the structures according to Wade's electron-counting methods

Abstract This is a survey of the preparation and structural properties of the intermetallic phases of gallium and alkali metals. Unlike the already known phases of gallium with lithium or sodium, the structures of the recently discovered phases Li3Ga14, Na22Ga39, KGa3, K3Ga13, RbGa3, RbGa7, and CsGa7 are characterized by stackings of coordinated gallium polyhedra such as icosahedra, octadecahedra, dodecahedra, and undecahedra. In these phases the alkali metals stabilize the gallium framework by giving their valence electrons. On this basis, the structures are interpreted according to Wades electron-counting procedure, bringing the Zintl phases to a more general concept and enhancing the interest on the transition forms between metallic and ionic bonding.

A new intermetallic phase K4Na13Ga49.57: synthesis and X-ray crystal structure

K4Na13Ga49.57 crystallizes in space group R3m with the lattice constants a = 16.399(4), c = 35.479(9) A, ca = 2.163, Z = 6. Diffraction data with 4 ≤ 2θ ≤ 50° (MoKα radiation) were collected on a Nonius CAD4 diffractometer within the two octant hkl and hkl. The structure was solved by trial methods and refined by full-matrix least-squares to a final R(F) = 0.079 for 1084 independent reflections with I > 3σ(I). The structure of K4Na13Ga49.57 contains gallium icosahedra and a curious novel 27-vertex, 28-atom polyhedral cluster linked to each other through direct interpolyhedral bonds to constitute a three-dimensional anionic lattice whose holes and cavities are filled with the alkaline cations.

Homoatomic polyanions of post-transition elements. Synthesis, structure and characterization of the paramagnetic nonagermanide (3 –) ion Ge3–9, a C2v cluster with an odd skeletal electron count

The salt K3(2,2,2-cryptand)3(PPh3)3Ge9 has been obtained by complexation of the KGe1.8 alloy by 2,2,2-cryptand in ethylenediamine with solute triphenylphosphine. The structure of the anion has been determined crystallographically and the results are supported by EPR and extended Huckel calculations.

Intermetallic phases of gallium and alkali metals: Synthesis and Structure of the nonstoichiometric phase K3Li9Ga28.83

Abstract The nonstoichiometric phase K 3 Li 9 Ga 28.83 has been obtained by reduction of Li 3 Ga 14 by potassium. The crystal is orthorhombic, space group Cmcm with a = 25.794(6) A, b = 18.911(5) A, and c = 13.497(3) A, Z = 8. Diffraction data with 4° ≤ 2ϑ ≤ 50° (Mo Kα radiation) were collected on a Nonius CAD 4 automatic diffractometer within the octant hkl . The structure was solved by direct methods and refined by full-matrix least squares to a final R ( F ) of 4.7% for 1096 independent reflections with I > 3 σ ( I ). K 3 Li 9 Ga 28.83 displays a very intricate structure built on incomplete icosahedral clusters of gallium arranged on a three-dimensional anionic lattice. The structure is stabilized by alkaline cations filling holes and channels. The nonstoichiometry has been interpreted in terms of geometrical and electronic considerations according to Wades electron-counting procedure for clusters.

Synthesis and crystal structure determination of the new intermetallic phase Li13Cu6Ga21

Abstract Li13Cu6Ga21 crystallizes in a cubic structure, space group Im3, with a = 13.568(2) A, Z = 4. Diffraction data were collected on a NONIUS CAD 4 diffractometer in the range 4 ≤ 2θ ≤ 50° (MoKα radiation). The structure was solved by direct methods and refined by full-matrix least-squares to a final R(F) = 0.033 for 346 independent reflections with I > 3σ(I). Li13Cu6Ga21 presents an interesting structure composed of Samsons polyhedral clusters (104 atoms) linked to each other through smaller junction polyhedral clusters (truncated tetrahedra and hypho-13-vertex polyhedra) containing lithium atoms in their centers.

Synthesis and crystal structure determination of the new ternary intermetallic phase Na17Cu6Ga46.5 (Na102Cu36Ga279)

Na17Cu6Ga46.5 crystallizes in the trigonal system, space group R3m with a = b = 16.183(6), c = 35.190(9) A; Z = 6. Diffraction data were collected on a Nonius CAD 3 diffractometer within the octants hkl and hkl of the corresponding A-centered monoclinic cell (a = 14.993(6), b = 16.184(7), c = 25.254(8) A; β = 119.75(5)°). The 5091 reflections were transformed and averaged into 1216 observed (I > 3σ(I)) in the R3m space group. The structure was solved by direct methods and refined by full-matrix least-squares to a final R(F) = 0.056. The structure of Na102Cu36Ga279 contains icosahedra displaying two types of symmetry and a triply fused icosahedron which forms a very unusual polyhedral complex with a copper atom (M28CuM28). Clusters are linked to each other to form an intricated three-dimensional anionic lattice. Sodium cations lie inside 12-vertex (Friauf), 15-vertex, and 16-vertex polyhedral cavities. This stoichiometric phase has been interpreted in terms of electron-deficient bonding within clusters and localized (2c-2e) bonding between clusters. In association with the extended Huckel molecular orbital (EHMO) calculation, the Wade-Mingos electron counting procedure applies successfully.

A strong symmetrical N–H–N bond. A 120 K neutron diffraction study of hydrogen diquinuclidinone perchlorate

Neutron diffraction studies provide evidence for the existence of the hydrogen diquinuclidinone homoconjugated cation containing a very short and symmetrical linear N–H–N hydrogen bond [N ⋯ N = 2.635(2)A and N–H = 1.317 (1)A].

New nickel gallium boride, B14Ga3Ni27: synthesis and crystal structure.

Crystals of the new compound B(14)Ga(3)Ni(27) were successfully prepared by arc melting of the elements. B(14)Ga(3)Ni(27) crystallizes as a novel structure type in the monoclinic space group P2(1)/m with unit cell parameters a = 8.6859(4) Å, b = 10.7477(4) Å, c = 8.8425(3) Å, β = 90.707(4)°, and Z = 2. Its structure was solved from single crystal data and refined to R1(F) = 0.0225. The unit cell of B(14)Ga(3)Ni(27) contains boron dumbbells and isolated gallium atoms embedded in a nickel 3D-framework. Its electronic structure, calculated by DFT methods, indicates metallic properties.

Heteroatomic polyanions of post-transition elements. Synthesis and structure of a salt containing the novel hybrid hepta-arsenic tetraselenate(1–) anion, As7Se4–

Rduction of As4Se4 by potassium in ethylenediamine in the presence of tetraphenylphosphonium bromide resulted in the formation of the compound P(C6H5)4·As7Se4 whose structure has been determined crystallographically.

Heteroatomic polyanions of post-transition elements. Synthesis and structure of a salt containing the undeca-arsenictellurate(3–) anion, As11Te3–

Reaction of the K1.6As1.6 Te alloy with the cryptand ligand N([CH2]2O[CH2]2O[CH2]2)3N in ethylenediamine (en) results in the formation of a compound formulated as [K(crypt )]3 As11Te·en, the anion geometry of which has been established by X-ray analysis.