La3Cl3BC – Structure, Bonding and Electrical Conductivity

Abstract

A new rare earth carbide boride halide, La3Cl3BC, has been prepared by heating a mixture of stoichiometric quantities of LaCl3, La, B and C at 1050 °C for 10 days. La3Cl3BC (La3Br3BC type) crystallizes in the monoclinic system with space group P21/m (No. 11), a = 8.2040(16), b = 3.8824(8), c=11.328(2)Å , β =100.82(3)°. In the structure, monocapped trigonal prisms containing B-C units are condensed into chains along the b direction, and the chains are further linked by Cl atoms in the a and c directions. The condensation results in a polymeric anion 1 ∞[BC] with a spine of B atoms in a trigonal prismatic coordination by La, and the C atoms attached in a square pyramidal coordination. The B-B and B-C distances are 2.16 and 1.63 Å , respectively. La3Cl3BC is metallic. The EH calculation shows that the distribution of valence electrons can be formulated as (La3+)3(Cl−)3(BC)5− · e−.