Tetsuzo Ito

Refinement of the structure of MgAlB14

The structure of MgAlB14 (space group, Imam; a = 5.848(1) A; b = 8.112(1) A; c = 10.312(1) A; Z = 4) was reinvestigated using single-crystal X-ray diffractometry. The crystal was grown from a high temperature AlB melt containing a small quantity of magnesium. A total of 1277 unique reflections (Mo Kα radiation; 2θ < 100°) was collected and used in a block diagonal leastsquares refinement to a final R value of 0.023. The boron framework in the crystal is the same as that reported by Matkovich and Economy. However, the distribution of the metal atoms is significantly different, i.e. no aluminium atoms are present at the magnesium site which is split into two positions separated by 0.39 A. The occupancies of the metals are 78% and 75% for the magnesium and aluminium sites respectively. The chemical composition determined by the structure analysis is Mg0.78Al0.75B14. Re-examination of the structure using the previously published intensity data indicates that the reported crystal probably had the same chemical composition and metal distributions as the present crystal.

Single-crystal X-ray diffraction study of AlB31 of the β-rhombohedral boron structure

Abstract The structure of a crystal with the composition AlB 31 , prepared by arc-melting crystals of α-AlB 12 , has been investigated by single-crystal X-ray diffractometry. The space group is R 3 m (No. 166) with the hexagonal cell dimensions a = 10.965(1) A and c = 23.868(2) A. The structure was refined by a fullmatrix least-squares program to an R ( R w ) value of 0.034(0.040). The three-dimensional boron framework of the crystal is essentially equivalent to that of β-rhombohedral boron. The aluminum atoms partially occupy A 1 and D holes in the boron framework, and in the D hole the aluminum atoms are distributed over five positions. A disordered structure around the single B(15) atom site is discussed in connection with the Al distribution in the D hole.

Deformation of the valence electron distributions in the icosahedral boron structure of α-AlB12

Abstract X-ray difference electron densities in α-AlB12 were examined. Broad peaks presumably characteristic of highly delocalized three-center bonds were observed at the centers of the triangular faces of the B12 icosahedron. Another kind of prominent peak on the external BB bonds of the icosahedron indicated that the inter-icosahedral BB bonds are two-center bonds. An averaging over the icosahedral symmetry significantly reduced the random noises in the difference densities. Theoretical difference electron densities for a B12H−212 molecular ion, calculated by the CNDO 2 molecular orbital method, were qualitatively in good agreement with the observed densities mentioned above. Residual peaks were observed on all the five edges of the open pentagonal face of the B19 unit; they had broad tails extending toward the aluminum triplet sites. The observed difference densities around the “single” B(23) atom suggested that the atom belongs to the B19 unit rather than being single.

Linear-chain bis(μ-O,O′-di­methyl di­thio­phosphato)­lead(II)

The title compound, [Pb(C2H6O2PS2)2], has a twofold rotation axis passing through the Pb atom along the b axis. One of the two unique S atoms in a formula unit and its symmetry-equivalent S atom bridge two adjacent Pb atoms, forming a polymeric linear chain along the c axis. The Pb atom is coordinated by six S atoms in a distorted octahedral arrangement. The six Pb—S distances are in the range 2.860 (2)–3.145 (2) A, with an average of 3.01 (8) A.

Tris(O-methyl di­thio­carbonato)­cobalt(III)

In the title complex, [Co(C2H3OS2)3], the Co atom is coordinated by six S atoms in a distorted octahedral arrangement. The six Co—S bond distances are in the range 2.262 (1)–2.275 (1) A, with an average of 2.270 (2) A.

Tris(O‐methyl­di­thio­carbonato)­chromium(III)

In the title complex, [Cr(C2H3OS2)3], the Cr atom is coordinated by six S atoms in a distorted octahedral arrangement. The six Cr—S bond distances are in the range 2.391 (1)–2.406 (1) A, with an average of 2.397 (2) A.