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Crystal Structures of the Metal Diborides ReB 2 , RuB 2 , and OsB 2 from Neutron Powder Diffraction
Author(s) -
Frotscher Michael,
Hölzel Markus,
Albert Barbara
Publication year - 2010
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.201000101
Subject(s) - isostructural , neutron diffraction , crystallography , boron , materials science , crystal structure , metal , powder diffraction , chemistry , metallurgy , organic chemistry
Because of the very small scattering power of the light element, the crystal structures of metal borides that contain heavy metal atoms are difficult to determine unambiguously from X‐ray diffraction data only. Using neutron diffraction methods and applying them to isotopically enriched 11 B boride powders, the crystal structures of ReB 2 , RuB 2 , and OsB 2 were re‐determined and analysed with respect to the boron atom arrangement. In accordance with the findings from X‐ray diffraction experiments, the structures exhibit corrugated boron atom layers of conjugated six‐rings, either seat‐like (ReB 2 ) or boat‐like (RuB 2 , OsB 2 ). ReB 2 crystallises in the hexagonal crystal system, space group P 6 3 / mmc (no. 194, a = 290.05(1) pm, c = 747.72(1) pm); OsB 2 and RuB 2 are isostructural and crystallise orthorhombically, space group Pmmn (no. 59, a = 464.479(5) pm, b = 286.515(3) pm, c = 404.560(6) pm (RuB 2 ); a = 468.408(5) pm, b = 287.255(3) pm, c = 407.693(6) pm (OsB 2 )). Boron–boron distances vary between 181.7 and 189.9 pm. For RuB 2 and OsB 2 , shortest metal‐boron distances range from 217.2 to 217.3 pm, indicating a covalent interaction between metal and boron, compared to 222.7 pm for ReB 2 . Metal–metal distances are between 286.5 pm and 302.2 pm. All three compounds have been described as very hard or incompressible materials.