Bond bridging ligands

The so-called shish kebab or Schaschlik approach allows the construction of stacked macrocyclic metal complexes such as phthalocyaninatometal complexes, metal complexes of tetrabenzoporphyrin, and octaethylporphyrin with variable distances between the planar macrocycles. The macrocycles are linked together by bisaxially metal-bonded bridging ligands thereby combining them... 

Covalent Bonded Bridging Ligands for Self-Supported Catalysts... 

The CK" ion can act either as a monodentate or bidentate ligand. Because of the similarity of electron density at C and N it is not usually possible to decide from X-ray data whether C or N is the donor atom in monodentate complexes, but in those cases where the matter has been established by neutron diffraction C is always found to be the donor atom (as with CO). Very frequently CK acts as a bridging ligand - CN- as in AgCN, and AuCN (both of which are infinite linear chain polymers), and in Prussian-blue type compounds (p. 1094). The same tendency for a coordinated M CN group to form a further donor-aceeptor bond using the lone-pair of electrons on the N atom is illustrated by the mononuclear BF3 complexes... 

Figure 27-10 Anhydrous acetates of Pd" and Pt" (a) trimeric [Pd(02CMe)2h involving square-planar coordinated Pd but no metal-metal bonding (average Pd -Pd = 315pm), and (b) tetrameric [Pt(02CMc)2]4 involving octahedrally coordinated Pt and metal-metal bonds (average Pt-Pi = 249.5 pm). llie four bridging ligands in the Pt,j plane are much more labile than the others.

The long Pt-Pt bond (2.694 A) follows the trend observed in rhodium dimers as the number of bridging ligands decreases (Figure 3.98). 

If this complex now collapses, it will be the labile Co-Cl bond which is broken, as opposed to the inert Cr-Cl bond. The labile cobalt(ii) complex reacts further with bulk water to generate [Co(H20)6] (Eq. 9.37). The key feature is that a necessary consequence of this inner-sphere reaction is the transfer of the bridging ligand from one center to the other. This is not a necessary consequence of all such reactions, but is a result of our choosing a pair of reactants which each change between inert and labile configurations. In the reaction described above, the chloride... 

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