Ligand substitution reactions exchange

Water-soluble derivatives of alkylidenes 8 and 9 were prepared via phosphine ligand substitution reactions. Exchange of the phosphines in 8a for PhP(p-C6H4S03-Na)2 afforded a water-soluble vinyl alkylidene [20]. This alkylidene was soluble in water, but the triarylphosphine ligands were too small and insufficiently electron-donating to produce an active catalyst [48], Analogous substitution of the phosphines in 9 a for more sterically demanding, electron-rich, water-soluble phosphines yielded ruthenium alkylidenes 10 and 11 (Scheme 2), which were soluble in both water and methanol [49]. 

A final example concerns the question to what extent a multiple series of ligand substitution reactions can lead to the irreversible exchange of two metal centers. The system studied in our laboratories involved the exchange of Mn and Cr in the series of reactions shown in Scheme 3 (93). 

CN-stretching frequencies, 12 387 kinetic data for, 12 413 ligand substitution reactions, 12 406 Pentacyanocobalt(II) exchange reactions of, 10 201, 202 kinetic data for, 10 202... 

One of the first differences to be noted about the Rhm acido-amine complexes is that the chloro complexes are frequently much more stable with respect to solvolysis than their Co111 and Cr111 analogues and solvolytic equilibrium is reached when very little of the chloro complex has aquated, even in dilute solution and in the absence of added chloride ions. This is, to some extent, the consequence of the move away from class a character already mentioned above. As a result, the rate constants for aquation are obtained from ligand substitution reactions (including chloride exchange) which first have to be shown to be mediated by a rate determining aquation. More recently, data have been obtained from a study of the solvolysis in basic solution. This serves to... 

Substitution of several metal-carbonyl complexes Cr(CO)6 and Mn(CO)5 (amine) show a small dependence on the nature and concentration of the entering hgand. Under pseudo-first-order conditions, the rate laws for these substitutions have two terms, as shown for Cr(CO)6 (as for some substitution reactions with 16e complexes, see equation 5). The second-order term was always much smaller than the first-order term. A mechanism that ascribes the second-order term to dissociative interchange (U) has been suggested for the Mo(CO)5Am system (Am = amine) and involves a solvent-encased substrate and a species occupying a favorable site for exchange. Thus, the body of evidence for the simple metal carbonyls indicates that CO dissociation and is the mechanism of ligand substitution reactions. 

We discuss a few ligand substitution reactions to give you a feel for the properties and reactions of coordination complexes. These simple reactions are aptly named one or more ligands are simply substituted for one another. We have already discussed one example of a series of ligand substitution reactions the exchange of NH3 and CP in Werner s cobalt complexes. 

THE SIMPLEST LIGAND SUBSTITUTION REACTIONS SOLVENT EXCHANGE 353... 

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