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ABSTRACT: The reaction of carbon and CaH(2) in a calcium/lithium flux mixture produces crystals of the new compound Ca(2)LiC(3)H. This phase forms with a new structure type in tetragonal space group P4/mbm (a = 6.8236(1) Å, c = 3.7518(1) Å, Z = 2, R(1) = 0.0151). This is a stuffed variant of the Cs(2)(NH(2))N(3) structure, containing hydride anions in octahedral sites; the structure determination by single-crystal X-ray diffraction surprisingly allowed the hydrogen to be detected. The Ca(2)LiC(3)H structure also features the rarely seen C(3)(4-) carbide anion; the protolysis reaction of this compound with ammonium chloride produces C(3)H(4). The electronic properties of Ca(2)LiC(3)H were studied by quantum-chemical calculations including band structure and electron localization function (ELF) analysis; the phase is a charge-balanced semiconductor with a calculated band gap of 0.48 eV. This is in agreement with (7)Li, (13)C, and (1)H MAS NMR data, which show resonances in the ionic region instead of the Knight shifted region. ELF analysis of the theoretical nonhydrided Ca(2)LiC(3) structure confirms the ability of these calculations to properly locate hydrides and supports the structural model based on X-ray diffraction data.
Journal of the American Chemical Society 11/2010; · 9.91 Impact Factor
