Bidentate binuclear bridging complex

In the binuclear complex, [(bpy)2(0H2)Zn(p2-C03)Zn(bpy)2] (N03)2-7H20 (F), the two N4-bound Znx and Zn2 ions are bridged by carbonate in monodentate and bidentate modes, the Znx being coordinated to one H20. Both the zinc ions are octahedrally coordinated with a relatively greater degree of distortion at Zn2 due to the chelating mode of the carbonate bridge. In these binuclear carbonate complexes of Zn(II) and Cu(II) an unexpected behavior, viz. Zn-0 distances < distances for carbonate coordination, was reported (341). 

There are also a few dimeric complexes containing a bridging bidentate ligand. Particularly noteworthy are the binuclear dinitrogen complexes [ RhH(PR3)2 2N2] (R = Pr1,55 Cy55,56). 

The dihydroxo-bridged binuclear complexes are among the most common, structurally well-characterized polynuclear complexes. For symmetrical bidentate nonbridging ligands, LL, the cation (LL)2M(OH)2M(LL)2"+ may exist in three isomeric forms a meso isomer (A,A) with configuration A and A, respectively, at the two metal centers, and a racemic pair of isomers (A,A and A, A) with configuration A or A at each of the two metal centers (cf. Fig. 2). If the bidentate... 

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