Monodentate ligands, cyanide-bridged complexes

As noted previously, a second large class of cyanide-bridged trinuclear complexes is characterized by a structure in which the central metal ion is either solvated or protected by one tetradentate, two bidentate, or four monodentate blocking ligands (Table IV). In the majority of these compounds, the peripheral building blocks act as donors of bridging cyanides to the central metal ion. 

When four monodentate ligands, including solvent molecules, are bound to the central metal ion, a trans disposition of the bridging cyanides is the preferred orientation [Fig. 18(c)]. The only exception to this trend is found in the structure of cw- [(pcq)Fe (CN)3l2[Mn (Me0H)2(H20)2] (119) [Fig. 18(kinetic products, given the presence of terminal cyanides or labile solvent molecules in their structures. The availability of these potential coordination sites renders such trinuclear complexes convenient scaffolds for the assembly of higher nuclearity clusters or extended structures (Section V). 

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