Ca₁₂InC_{13–<i>x</i>} and Ba₁₂InC₁₈H₄: Alkaline-Earth Indium Allenylides Synthesized in AE/Li Flux (AE = Ca, Ba)

Abstract

Two new complex main-group metal carbides were synthesized from reactions of indium, carbon, and a metal hydride in metal flux mixtures of an alkaline earth (AE = Ca, Ba) and lithium. Ca₁₂InC_{13–<i>x</i>} and Ba₁₂InC₁₈H₄ both crystallize in cubic space group <i>Im</i>3̅ [<i>a</i> = 9.6055(8) and 11.1447(7) Å, respectively]. Their related structures are both built on a body-centered-cubic array of icosahedral clusters comprised of an indium atom and 12 surrounding alkaline-earth cations; these clusters are connected by bridging monatomic anions (either H^– or C^4–) and allenylide anions, C₃^4–. The allenylide anions were characterized by Raman spectroscopy and hydrolysis studies. Density of states and crystal orbital Hamilton population calculations confirm that both compounds are metallic