Ca₁₂InC_13–x 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. Ca(12)InC(13-x) and Ba(12)InC(18)H(4) 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 C(4-)) and allenylide anions, C(3)(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.

Low-Dimensional Nitridosilicates Grown from Ca/Li Flux: Void Metal Ca8In2SiN4 and Semiconductor Ca3SiN3H

“…This confinement may cause a low work function, which makes void metals potential candidates as IR sensors. The class of “void metals” may be expanded to include subvalent hydrides and carbides, as exemplified by Ca 54 In 13 B 4‑ x H 23+ x and Ca 12 InC 13‑ x . , Ca 8 In 2 SiN 4 offers the first example of a void metal with a complex nitridosilicate anion; DOS calculations also support this (vide infra).…”

“…Formation of Ca 3 SiN 3 H results from hydride contaminants present in calcium metal. Previous compounds synthesized by this group including Ca 54 In 13 B 4‑ x H 23+ x , Ba 12 InC 18 H 4 , LiCa 3 As 2 H, and Ca 2 LiC 3 H also stem from hydride incorporation into products when calcium is used as purchased. ,,, Reactions similar to those which produced Ca 3 SiN 3 H were done with purified calcium to eliminate hydride contamination from the calcium metal and to explore what products form in the absence of a hydride source. Indeed, the use of purified calcium prevented formation of Ca 3 SiN 3 H and instead produced α-Ca 5 Si 2 N 6 and an unidentified silvery metallic cubic phase.…”

“…Recent work in our lab has focused on the use of Ca/Li flux. The successful growth of new carbide, hydride, and nitride phases such as Ca 12 InC 13‑ x , Ca 54 In 13 B 4‑ x H 23+ x , Ca 11 Sn 3 C 8 , and Ca 6 Te 3 N 2 from this melt indicates that further exploration is merited. − Calcium metal melts above 800 °C, but a 1:1 mixture of calcium with lithium metal melts at 300 °C. Such lowered temperatures enable incorporation of calcium into metastable nitride products; lithium more often acts as a spectator in the low temperature reaction, but will incorporate into products occasionally (as seen for Ca­(Li x Fe 1– x )­Te 2 N 3 , LiCa 3 As 2 H, and Ca 2 LiC 3 H). − …”

Flux Synthesis of a Metal Carbide Hydride Using Anthracene As a Reactant

“…Slow cooling of the solution allows products to be isolated as crystals . Our group has explored synthesis in a variety of rare earth/transition metal (R/T) eutectic flux mixtures; these fluxes are excellent solvents for carbon and have yielded metal carbides such as La 21 Fe 8 Sn 7 C 12 , Ce 33 Fe 13 B 18 C 34 , and Pr 62 Fe 21 Si 16 C 32 . − Complex metal hydrides can be readily synthesized in fluxes containing alkaline earth metals, as indicated by the formation of LiCa 7 Ge 3 H 3 and Ca 54 In 13 H 27 from reactions of CaH 2 with other elements in Ca/Li melts. , Alkaline-earth-based fluxes have also yielded metal carbide hydrides, including LiCa 2 C 3 H from Ca/Li and Ba 12 InC 18 H 4 from Ba/Li melts. , …”

Metal Nitrides Grown from Ca/Li Flux: Ca6Te3N2 and New Nitridoferrate(I) Ca6(LixFe1–x)Te2N3

“…While electronegative main group elements are especially soluble in electropositive Ca/Li mixtures, light elements are also highly reactive in these melts. Previous reactions utilizing Ca/Li flux have produced compounds such as Ca 12 InC 13– x , Ca 54 In 13 B (4– x ) H (23+ x ) , Ca 11 E 3 C 8 (E = Sn, Pb), LiCa 3 As 2 H, LiCa 7 Ge 3 H 3 , and Ca 2 LiC 3 H. − Based on the successful syntheses of complex metal carbides and hydrides from refractive light element sources, it was postulated that Ca/Li flux may also be useful for the synthesis of complex nitrides.…”