Adenosine 3’-O(PO2-)OCH(2)R phosphate esters have been-synthesized with R = 8-hydroxyquinol-2-yl (1a) and 8-(hydroxyquinolyl)-2-methylene (1b). The adenosine 3’-O(PO2-)OCH(2)R structure has the essential features of an RNA dinucleotide. Equilibrium binding studies with metal ions Mg2+, Zn2+, Cu-2+, and La3+ have been carried out with 1a, 1b, HOCH(2)R (7a and 7b), and 8-hydroxyquinoline (8), and equilibrium constants (K-as) have een determined for the formation of 1:1 (L)M(n+) complexes. The hydrolysis of 1a and 1b as well as (1a)M(n+) and (1b)M(n+) species are first order in HO-. The rate enhancement for hydrolysis of 1a by complexation with metal ions is as follows : similar to 10(5) with Zn2+, similar to 10(7) with Mg2+, similar to 10(5) with Cu2+, and similar to 10(9) with La3+. Molecular modeling indicates that metal ions ligated to the 8-hydroxyquinoline moiety in the complexes (1a)M(n+) and (1b)M(n+) catalyze 1a and 1b hydrolysis by interacting as Lewis acid catalysts with the negatively charged oxygen atom of the phosphate group. In the instance of La3+ complexes, the ligated metal ion is within an interactive distance with both the negative phosphate oxygen and the leaving oxygen. This bimodal assistance by La3+ to the displacement reaction at phosphorus by the 2’-hydroxyl anion results in remarkable rate accelerations for the hydrolysis of (1aLa3+ and (1bLa3+ complexes. The complexes (1a)M(n+) and (1b)M(n+) are themselves hydrolyzed by metal ion catalysis in a reaction that is first order in HO-, an observation consistent with a transition state composition of [(1a,b)M(n+)][M(n+)][HO-]. We assume the kinetic equivalent [(1a,b)M(n+)][M(n+)OH] to represent the reacting species. In this catalysis the M(n+)OH is proposed to play the role of general base to deprotonate the 2’-OH while the metal in the complexes (1a,b)M(n+) is coordinated to a negative oxygen of the -(PO2-)- moiety. This double metal ion catalysis mimics a mechanism proposed for the ribozyme self-cleavage of RNA.