Kinetic and mechanistic studies on the complexation and anation of dioxotetracyanomolybdate (IV) with 2,2′-bipyridyl in aqueous solution

Dioxotetracyanomolybdate(IV) has been found to form a 1 : 2 complex with 2,2′-bipyridyl. The kinetics of the reaction has been studied over the pH range 5.3–8.7 by visible spectrophotometry under pseudo conditions. The effect of the 2,2′-bipyridyl and dioxotetracyanomolybdate(IV), temperature, ionic strength, and pH on the reaction rate was determined. The reaction follows first-order kinetics with respect to dioxotetracyanomolybdate(IV) ion and fractional-order kinetics with respect to 2,2′-bipyridyl. Values for the outer-sphere complex formation constant (K_os2) and rate constants (k₂) were also calculated from the kinetic data. It was found that rate of the reaction increases with the decreasing pH. The following rate equation based on the outersphere complexation equilibrium preceding the associative interchange has been derived. On the basis of the observed results probable mechanism has been proposed. © 1996 John Wiley & Sons, Inc.