Complexes containing naked dicarbon ligands

There is an interesting series of heterobinuclear complexes in which the Ru and Zr centers are connected by three different types of C2 bridges C-C, C=C, and C=C. 

Acetylene is a Brpnsted acid (pA), 25). Its chemistry is associated with its triple-bond character and the labile hydrogen atoms. It can easily lose one proton to form the acetylide monoanion HC=C-(IUPAC name acetylenide) or release two to give the acetylide dianion C=C (C22-, IUPAC name acetylenedi-ide). The acetylenide H-C=C and substituted derivatives R-C=C- form organometallic compounds with the alkali metals. In these compounds, the interactions of the n orbitals of the C=C fragment with metal orbitals may lead to many structural types, e.g., 

Crystal structure of (a) tetragonal CaC2 I (Mfmmm, Z = 2) (b) cubic CaC2 IV (Fm3m, Z = 4), the dumbbell exhibits orientational disorder (c) 

Crystal structure of (a) KAgC2 (PMmmm, Z = 1) (b)LiAgC2 (P6m2, 

Polyhedral Agn (n = 6-9) cages with encapsulated C22 species found in various silver(I) double salts  

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