Structure and bonding in ternary and quaternary transition metal carbides and carbide silicides containing linear M=C=M units

Linear infinite chains of Co=C=Co) units are found in the structure of LnCoC derivatives (Ln = Y or lanthanides). Similar linear M=C=M units can be used to construct the infinite two-dimensional networks of Ln2M2C3 structures (M = Cr, Mo). In addition linear M=C=M units link the double butterfly chains in the quaternary metal carbide silicides Ln2M2Si2C and LnM2SiC. This paper discusses chemical bonding, electron counting, and formal metal oxidation states in these solid state structures.