Solvento complexes ligands

In Chapter 3 we considered methods of formation of solvento-complexes and illustrated the various ways these compounds are prepared. Halide abstraction techniques that utilize silver salts are commonly employed in the synthesis of mixed-ligand solvento-complexes and such techniques are used also for the transformation of halide complexes into homoleptic solvento-complexes. 

In the earliest authentic halocarbon complex (1982), o-diiodobenzene was found to chelate to cationic Ir(III) as shown in diagram (5). An earlier proposed example proved to be misidentified when the crystal structure was carried out. To be stable, any such complex must resist oxidative addition, hence the use of an oxidation state, Ir(III), that is only oxidized with difficulty. The normally rather weakly basic halocarbon lone pairs are often reluctant to bind, but chelation and involvement of the least electronegative halide, iodine, favor binding as does the cationic character of the complex. A series of such complexes was soon found, including complexes of Ir(I) and a series of weakly bound dichloromethane complexes for certain systems. These solvento complexes can be very labile and so find use as precursors for binding of other weakly basic ligands. Even fluorocarbon complexes proved viable.A review of the area is available. It now seems... 

These solvent ligands can be quite labile, and, for this reason, the solvento-complexes themselves are often useful catalyst precursors, as discussed in a recent review by Davies and Hartley. ... 

Associative mechanisms for ligand exchange in tetrahedral complexes of transition metals have been reported in several cases. Studies of tetrahedrally distorted copper and nickel complexes have already been mentioned above (see Chapter 2, refs. 131 and 133). Activation parameters for the solvent exchange in the tetrahedral nickel(ii) solvento complex in hexamethylphosphoramide, determined using n.m.r. spectroscopy, are compatible with an associative... 

Lanthanide Complexes with Multidentate Ligands Lanthanide Oxide/Hydroxide Complexes Lanthanides Coordination Chemistry Solvento Complexes of the Lanthanide Ions Trivalent Chemistry Cyclopentadienyl. 

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