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Sr 10 [Mo 2 N 6 ][MoN 4 ] 2 and β‐Sr 3 MoN 4
Author(s) -
Bailey Mark S.,
McGuire Michael A.,
DiSalvo Francis J.
Publication year - 2004
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.200400081
Subject(s) - triclinic crystal system , orthorhombic crystal system , crystallography , molybdenum , strontium , crystal structure , nitride , space group , materials science , x ray crystallography , chemistry , analytical chemistry (journal) , inorganic chemistry , diffraction , nanotechnology , physics , organic chemistry , layer (electronics) , chromatography , optics
Two new phases in the strontium‐molybdenum‐nitrogen phase diagram have been synthesized. Single crystals of Sr 10 [Mo 2 N 6 ][MoN 4 ] 2 were grown from a mixed sodium‐gallium melt at 900 °C in a sealed niobium tube. It crystallizes in the triclinic space group $P{\bar 1}$ (Z = 1) with a = 6.421(1), b = 9.190(2), c = 9.263(2) Å and α = 64.939(5), β = 82.961(6) and γ = 89.692(6)°. The new, orthorhombic polymorph of Sr 3 MoN 4 was synthesized as a polycrystalline powder from an intimate mixture of Sr 2 N and molybdenum metal in the presence of N 2 . Rietveld analysis shows it to crystallize in Pbca (Z = 8) with a = 10.4835(2), b = 9.7374(2) and c = 11.5114(2) Å. Studies suggest that excess nitrogen is essential to the formation of this polymorph. Sr 10 [Mo 2 N 6 ][MoN 4 ] 2 is the first molybdenum nitride to contain the anionic unit [Mo 2 N 6 ] 8‐ , which appears as isolated, edge‐sharing pairs of MoN 4 that facilitate Mo V ‐Mo V bonding. This compound also contains isolated [MoN 4 ] 6‐ tetrahedra and the presence of these two units results in the first mixed valent molybdenum nitride. Resistivity measurements show it to be insulating.