Organometallic motifs in the structures of solid state ternary carbides of the late transition metals

Abstract

Solid state ternary transition metal carbides containing carbon, a middle to late transition metal (Re to Ni), and a highly electropositive multivalent metal such as lanthanide, yttrium, or thorium exhibit a number of structural motifs resembling those in metal carbonyls and other transition metal derivatives of strong π-acceptor ligands. This paper presents models for the chemical bonding in the transition metal—carbon subnetworks of the ternary late transition metal carbides LnCoC (Ln=lanthanide), Ln2ReC2, Th2NiC2, Ln2FeC4, Ln3MC4 (M=Fe, Co, Ni, Ru, Rh, Os, Ir), Ln4NiC5, Ca4Ni3C5, and Er8Rh5C12. Carbide ligands present in such materials include terminal C4− in Th2NiC2 and Y2ReC2, μ2-C4− in YCoC or Y2ReC2 similar to the central allene carbon atom, 1,2-bridging C24− in Sc3CoC4 formally derived from ethylene, μ3-bridging C24− in LnMC2 (M=Fe, Co, Ni, Ru) formally derived from ethylene, and 1,1-bridging C22− in Ln2FeC4 isoelectronic with μ2-CO group in metal carbonyls.