Tosio Sakurai

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.

Crystal and molecular structure of tris(hexaamminerhodium(III)) tetrakis(trichlorostannato(II))(tetrachlorostannato(II)rhodate(I) hexachlorostannate(II) tetrahydrate

Abstract The crystal and molecular structure of the title compound, [Rh(NH3)6]3[Rh(SnCl3)4(SnCl4)] [SnCl6] · 4H2O, has been determined by the single-crystal X-ray diffraction method. The compound crystallizes in the monoclinic system, space group P2 n with a = 16.581(2), b = 11.010(4), c = 16.024(2)A, β = 90.76(1), and two molecules per unit cell. The structure was solved by Pattersons method and refined by the least-squares technique to give a final R factor of 0.031. The three cations, [Rh(NH3)6]3+, are a regular octahedron with an average RhN bond length of 2.07 A. The rhodium anion, [Rh(SnCl3)4(SnCl4)]5−, is a trigonal bipyramid with the two axial RhSn bonds, 2.493 A in length, and the three equatorial bonds, 2.546, 2.540, and 2.540 A. One of the three tin atoms in the equatorial trigonal plane forms a distorted trigonal bipyramid with two short SnCl bonds 2.384 A in length and two long bonds, 2.733 A. The other four tin atoms have a distorted tetrahedral arrangement with an average SnCl bond length of 2.42 A. The tin anion, [SnCl6]4−, which is not coordinated to rhodium, forms extremely long SnCl bonds of 2.763, 2.800, and 2.893 A in a distorted octahedral arrangement.

The Phase Transformation of Solid Normal Hexadecanamide

A phase transformation of normal hexadecanamide (C 15 H 31 CONH 2 ) in which the crossed hydrocarbon chain configuration changes into the parallel-chain one is investigated by means of X-rays, thermal analysis, infrared absorption and proton magnetic resonance absorption. Based upon the knowledge of the crystal structure and X-ray observation, a mechanism of successive reorientation of the hydrocarbon chain at this transformation is proposed. The twisting vibration of the hydrocarbon chain is found to play an important role for this transformation.

The Cross-Chain Configuration and a New Type of Phase Transformation in Solid Long Chain Acid Amides

From the X-ray investigation on the single crystal of long chain acid amides of even carbon number from C=10 to 18, three phases are found to exist. Phase A in palmitic, myristic, and capric acid amides has the unusual crossed chain configuration similar to that found in potassium soaps. In phase B, found in palmitic and stearic acid amides, and phase C, in stearamide under a special condition, chains are parallel as in the ordinary long chain compounds. All phases seem to be stable at room temperature, but phase A of palmitic amide transforms irreversibly into phase B by heating. But the basal plane is almost unchanged during the transformation.