Hydrolysis of Coordinated Nitriles and Linkage Isomerization Reactions in Ruthenium Ammine Complexes with Nitriles and Amides

This chapter surveys the hydrolysis of coordinated nitriles to amides in ruthenium ammine complexes, and the subsequent afterreduction of the amido-Ru(III) complex. Nitriles coordinated to Ru(II) can undergo hydrolysis to amides after oxidation of Ru(II) to Ru(III). The hydrolysis of the Ru(II/III)-1-R-cyanopyridinium complex leads to pure amide, whereas hydrolysis of the free ligand results in a mixture of amide and pyridone. The rate constants for the hydrolysis of different coordinated nitriles to amides span several orders of magnitude. Catalytic systems can be designed. Upon reduction of the resulting Ru(III)-amide, the isonicotinamide, nicotinamide, or acrylamide complexes undergo aquation and isomerization to form the pyridyl or the olefin-bonded complex. On reduction of the Ru(III)-2-picolinamido complex, aquation and chelation occur to form [Ru(NH3)5(H2O)]2+ and picolinamide, and cis-[Ru(NH3)4(2-picolinamide)]2+, respectively. The spectral properties of the nitrile and amide complexes of Ru(II) and u(III) ammines and the preferred coordination site in ambidentate ligands are also presented.