文摘
On the basis of a detailed study applying X-ray single-crystal and powder diffraction, differential scanning calorimetry, and scanning electron microscopy analysis, it was possible to resolve existing uncertainties in the Pt-rich section (鈮?5 atom % Pt) of the binary Pt鈥揃 phase diagram above 600 掳C. The formation of a unique structure has been observed for Pt<sub>2sub>B [X-ray single-crystal data: space group C2/m, a = 1.62717(11) nm, b = 0.32788(2) nm, c = 0.44200(3) nm, 尾 = 104.401(4)掳, R<sub>F2sub> = 0.030]. Within the homogeneity range of 鈥淧t<sub>3sub>B鈥? X-ray powder diffraction phase analysis prompted two structural modifications as a function of temperature. The crystal structure of 鈥?i>hT-Pt<sub>3sub>B鈥?complies with the hitherto reported structure of anti-MoS<sub>2sub> [space group P6<sub>3sub>/mmc, a = 0.279377(2) nm, c = 1.04895(1) nm, R<sub>Fsub> = 0.075, R<sub>Isub> = 0.090]. The structure of the new 鈥?img src="/appl/literatum/publisher/achs/journals/content/inocaj/2015/inocaj.2015.54.issue-22/acs.inorgchem.5b01998/20151110/images/ic-2015-01998v_m001.gif" alt="" />T-Pt<sub>3sub>B鈥?is still unknown. The formation of previously reported Pt<sub>鈭?sub>B has not been confirmed from binary samples. Exploration of the Pt-rich section of the Pt鈥揅u鈥揃 system at 600 掳C revealed a new ternary compound, Pt<sub>12sub>CuB<sub>6鈥?i>ysub> [X-ray single-crystal data: space group Im3虆, a = 0.75790(2) nm, y = 3, R<sub>F2sub> = 0.0129], which exhibits the filled WAl<sub>12sub>-type structure accommodating boron in the interstitial trigonal-prismatic site 12e. The isotypic platinum鈥揳luminum鈥揵oride was synthesized and studied. The solubility of copper in binary platinum borides has been found to attain 鈭? atom % Cu for Pt<sub>2sub>B but to be insignificant for 鈥?img src="/appl/literatum/publisher/achs/journals/content/inocaj/2015/inocaj.2015.54.issue-22/acs.inorgchem.5b01998/20151110/images/ic-2015-01998v_m002.gif" alt="" />T-Pt<sub>3sub>B鈥? The architecture of the new Pt<sub>2sub>B structure combines puckered layers of boron-filled and empty [Pt<sub>6sub>] octahedra (anti-CaCl<sub>2sub>-type fragment) alternating along the x axis with a double layer of boron-semifilled [Pt<sub>6sub>] trigonal prisms interbedded with a layer of empty tetrahedra and tetragonal pyramids (B-deficient 伪-TI fragment). Assuming boron vacancies ordering (space group R3), the Pt<sub>12sub>CuB<sub>6鈥?i>ysub> structure exhibits serpentine-like columns of edge-connected boron-filled [Pt<sub>6sub>] trigonal prisms running infinitely along the z axis and embedding the icosahedrally coordinated Cu atom. Pt<sub>2sub>B, (Pt<sub>1鈥?i>ysub>Cu<sub>ysub>)<sub>2sub>B (y = 0.045), and Pt<sub>12sub>CuB<sub>6鈥?i>ysub> (y = 3) behave metallically, as revealed by temperature-dependent electrical resistivity measurements.
