Ligand 7r-bonding

The data in Table I can be interpreted unambiguously—i.e., hydrolysis occurs through the metal-ligand 7r-bond. 

With the exception of the Ru complex, a variety of metal ions activate the hydration reaction to a very consistent extent (10 -10 -fold). The relative constancy of the rate acceleration and the anomaly of the complex are consistent with the view that it is the Lewis acidity of the metal ion which is essential for activation. In the Ru complex, considerable metal- ligand 7r-bonding is expected, resulting in back donation of electron density from the metal centre into the C=N bond. This view is supported by measurements of the C=N stretching frequency of free nitriles and of their complexes with Ru and the other metal ions. ... 

Fig. 20.14 Approximate partial MO diagrams for metal-ligand 7r-bonding in an octahedral complex (a) with 7r-donor ligands and (b) with 7r-acceptor ligands. In addition to the MOs shown, cr-bonding in the complex involves the a g and ti MOs (see Figure 20.12). Electrons are omitted from the diagram, because we are dealing with a general ion. Compared with Figure...

As an approximate method for the analyses of the relaxation data of Co systems without significant cobalt-ligand 7r-bonding, in Eq. (32) has... 

TT-Donor ligands include d , Br and 1 and the metal-hgand 7r-interaction involves transfer of electrons from filled ligand p orbitals to the metal centre (Figure 21.14a). Examples of 7r-acceptor ligands are CO, N2, NO and alkenes, and the metal-ligand 7r-bonds arise from the... 

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