Table S1. Atom positions and isotropic thermal parameters for Ca 52.7 In 13 B 1.6 H 25.4 (crystal 1) Wyckoff Site x y z occ U eq a

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.

The reaction of arsenic with sources of light elements in a Ca/Li melt leads to the formation of two new arsenide hydride phases. The predominant phase Ca14As6X7 (X = C(4-), N(3-), H(-)) exhibits a new tetragonal structure type in the space group P4/mbm (a = 15.749(1) Å, c = 9.1062(9) Å, Z = 4, R1 = 0.0150). The minor phase LiCa3As2H also has a new structure type in the orthorhombic space group Pnma (a = 11.4064(7) Å, b = 4.2702(3) Å, c = 11.8762(8)Å, Z = 4, R1 = 0.0135). Both phases feature hydride and arsenide anions separated by calcium cations. The red color of these compounds indicates they should be charge-balanced. DOS calculations on LiCa3As2H confirm a band gap of 1.4 eV; UV-vis spectroscopy on Ca14As6X7 shows a band gap of 1.6 eV. Single-crystal neutron diffraction studies were necessary to determine the mixed occupancy of carbon, nitrogen, and hydrogen anions on the six light-element sites in Ca14As6X7; these data indicated an overall stoichiometry of Ca14As6C(0.445)N(1.135)H(4.915).

New carbide Zintl phases Ca(11)E(3)C(8) (E = Sn, Pb) were grown from reactions of carbon and heavy tetrelides in Ca/Li flux. They form with a new structure type in space group P2(1)/c (a = 13.1877(9)Å, b = 10.6915(7)Å, c = 14.2148(9)Å, β = 105.649(1)°, and R(1) = 0.019 for the Ca(11)Sn(3)C(8) analog). The structure features isolated E(4-) anions as well as acetylide (C(2)(2-)) and allenylide (C(3)(4-)) anions; the vibrational modes of the carbide anions are observed in the Raman spectrum. The charge-balanced nature of these phases is confirmed by DOS calculations which indicate that the tin analog has a small band gap (E(g) < 0.1 eV) and the lead analog has a pseudogap at the Fermi level. Reactions of these compounds with water produce acetylene and allene.

Regions. -Ca 54In13B4-xH23+x (2.4 < x < 4) is prepared by solid state reactions of Ca, Li, In, B, and CaH 2 in the molar ratio of 10:10:1:1:1, resp., using Ca and Li as a flux (stainless steel container in evacuated silica tube, 1050 C, 2 h; controlled cooling). The compound crystallizes in the cubic space group Im3 (Z = 2, single crystal XRD) and exhibits a complex new structure comprising a body-centered cubic array of Bergman--related clusters that are composed of a central In atom surrounded by an icosahedron of 12 Ca atoms; Hions cap each face forming a pentagonal dodecahedron that is further surrounded by a Ca shell. These In@Ca 12@H20@Ca30 clusters are surrounded by a disordered Ca In hydride network. Indium appears to be not completely reduced by the flux, as the structure features ionic hydride regions and metallic Ca In regions. The compound can therefore be viewed as a "subhydride" akin to the alkali metal suboxides that feature ionic oxide clusters surrounded by metallic regions. -(BLANKENSHIP, T. V.; CHEN, B.; LATTURNER*, S. E.; Chem. Mater. 26 (2014) 10, 3202-3208, http://dx.