A KINETIC-STUDY OF THE REACTION BETWEEN [OSN(H2O)(CN)4]- AND AZIDE IONS IN AQUEOUS-SOLUTION

The kinetics of the substitution reaction between [OsN(H2O)(CN)4] and N3-showed that the nitrido ligand with its strong sigma- and pi-electron donor ability labilizes the osmium(VI) complex. The metal-oxygen bond strength decreases due to the large trans influence of the nitrido ligand, which allows substitution reactions with N3- at a rate of 1.89(7)M-1 s-1 at 25-degrees-C.[OsN(H2O)(CN)4] is a much weaker acid (pK(a1) = 7.49) compared to [OsO(H2O)(CN)4], as a result of the larger trans influence of N3- compared to O2-. A linear free energy relationship exists between the pK(a1)-values and the substitution rates for different[ML(H2O)(CN)4]n- complexes (M = Mo(IV), W(IV), Re(V) and Os(VI); L = O2- and N3-).