Reactivities of coordinated phosphodiesters

The amminolysis and hydrolysis of the ester moieties in [(NH3)5Co(bnpp)]2+ and cis-[(en)2Co(OH)(bnpp)]+ (where bnpp = bis(4-nitrophenylphosphate) and en = 1,2-ethanediamine) in aqueous solution at 25°C have been followed over a range in pH. In each instance, cleavage of 4-nitrophenol occurred in two observable events triggered by the coordinated nucleophiles, amido ion and hydroxo ion. The mechanistic pathways have been analyzed and the rate enhancements evaluated relative to uncoordinated substrates and other relevant literature data. The analysis indicates requirements for the metal reagent to be effective in phosphate ester hydrolysis and phosphoryl transfer.