Nd2[MoC2] and RE2[WC2], RE=Ce, Pr, Nd: New carbometalates with Pr2[MoC2] structure type

Four new ternary rare-earth-metal carbometalates, Nd2[MoC2] and RE2[WC2] with RE=Ce, Pr, Nd, have been synthesized by argon arc melting and subsequent heat treatment at 1170 K for 30 days. They crystallize with the Pr2[MoC2] structure type with isolated C4− species and are typical carbometalates with (i) low metal-to-carbon ratio, (ii) tetrahedral coordination of the transition metals (T) by carbon, and (iii) a polyanionic network ∞2[(TC2)6-]. According to resistivity measurements the compounds are bad metals. Volume chemistry and magnetic susceptibility measurements indicate Pr3+, Nd3+, and Ce4+ species, respectively. In the latter case, the additional electron is not transferred to the polyanionic network, instead it mainly populates the Ce partial structure.