Substitution Reactions without using a Solvent

In some reactions the ligand to be introduced is a liquid, and where there are no issues relating to a need for stoichiometric amounts of reagents it is possible to use the ligand in 

While this reaction works well with most anhydrous metal ion salts, it is not necessarily convenient because of the handling difficulties involving liquid ammonia, and some salts form isolable ammine complexes sufficiently well using aqueous ammonia, as is the case with Ni(II) and Cu(II), for example. 

Another approach, which permits introduction of anionic ligands of strong acids, is to react a complex containing coordinated chloride ion directly with an anhydrous strong acid, such as trifluoromethanesulfonic acid, in the total absence of any other solvent. One example, where HC1 is released as a covalent gas and leaves the anhydrous reaction mixture and the CF3SO3 anion enters the coordination sphere as an O-bound monodentate ligand, is reaction with chloropentaamminecobalt(III) chloride (6.19). 

This approach permits the insertion of a wide range of stable anions apart from chloride into the coordination sphere, simply by commencing with them present as the counter-ion. At higher temperature, amine ligands can be lost in the same manner that water is lost, and may occur in a stepwise process that permits isolation of useful intermediate complexes. Eventually, at sufficiently high temperature, all ligands are lost, as in (6.22). 

This reaction of Pt(II) is general for a range of coordinated amines apart from ammonia, and appears to yield exclusively the trans geometric isomer (which is called, because of this exclusivity, a stereospecific reaction). Even chelated diamines can be substituted, as they are inevitably more volatile than any anions present thus chelated 1,2-ethanediamine can be replaced by two chloride ions in [Co(en)3]Cl3 to form m-[CoCl2(en)2]Cl, and by 

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