Dinuclear covalently bridged

Even if one can create the SCO ligand-field around one end of a covalently-bridged dinuclear complex, the SCO might influence the ligand-field at the other end. There are many inter-dependent effects to bear in mind of a bonding, electronic and structural kind, and attempts to delineate these are given below. Inter-cluster or inter-chain effects will play difficult-to-control roles in crystalline SCO polynuclear materials, and these have already been alluded to for mononuclear complexes. 

The general dinuclear structural motifs are of the weakly linked, 1, or covalently-bridged, 2, types shown in which... 

Dinuclear zwitterionic spirosilicates were also synthesized and characterized by Tacke and coworkers (equations 22 and 23). These differ from previous dinuclear silicates in that they are bis-zwitterionic. The bridge in 87 is through the covalent bonding of a l,4-(dimethylene)piperazine, whereas in equation 23 a double bridge is formed by two tetradentate ligand molecules, tartaric acid. The crystal structure of 87 proved that the product was the meso compound, with opposite configurations at the silicon centers . When the reaction in equation 23 was run with optically active (l ,J )-(+)-tartaric acid the first optically active zwitterionic bis-silicate (88) was obtained . 

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