Pentaammines anation

IS further extended by the replacement of X by other anionic or neutral ligands. The inertness of the compounds makes such substitution reactions slow (taking hours or days to attain equilibrium) and, being therefore amenable to examination by conventional analytical techniques, they have provided a continuing focus for kinetic studies. The forward (aquation) and backward (anation) reactions of the pentaammines ... 

The hexaamine complex can only be prepared in sealed tube reactions (equation 34), unless the incorporation of the sixth ammine ligand is catalyzed by ethanol. In contrast, the pentaammine complexes are very accessible, and their anation and aquation reactions (Scheme 11) have been exhaustively... 

Z>) Reactions of [Rh(NH ),X. The aquation and anation of [Rh(NH3X]" in acidic aqueous solution (equation 105 was first studied by Lamb who used conductance changes to monitor the interconversion of acido and aqua rhodium complexes , for the chloro and bromopentaanimine-rhodium(III) cations. He found that both aquation and anation are first-order in [Rh ], and that the hydrolysis is accelerated by the presence of OH . The forward form of equation (105) (aquation) has since been studied for X = Cl-, Br , l-, >.=56 oHj, SO, NO3" and Nj . Representative results for the aquation of various pentaammine salts are given in Table 25. For aquations of halides or nitrate ions, rate expressions which are first-order in [Rh] and zero-order in [H+] are found. Poe gives a detailed discussion of the thermodynamic, kinetic and intrinsic-kinetic trans effects, and compares the aquation and anation of [Rh(NH3)5X]-" (X = Cl, Br and I) with the [RhfenjjXY]" system. When X = S04, a two-term rate expression was observed... 

Rate Constants for the Aquation of Pentaammine (ligand) cobalt(III) Complexes and Equilibrium Constants for the Anation of Pentaammineaquacobalt(III) with Various Anions... 

---