Ca12InC13–x and Ba12InC18H4: Alkaline-Earth Indium Allenylides Synthesized in AE/Li Flux (AE = Ca, Ba)

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. Ca12InC13–x and Ba12InC18H4 both crystallize in cubic space group Im3̅ [a = 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 C4–) and allenylide anions, C34–. 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.