Metal ion activation of phosphate transfer by bidentate coordination

The hydrolysis of methyl phosphate bound to the triethylenetetramine-cobalt(III) ion is much faster than the hydrolysis of either dimethyl phosphate bound to the same cation or methyl phosphate bound to the pentamminecobalt-(III) ion. The rate enhancement is attributed to bidenate coordination of the methyl phosphate. This feature suggests a pseudorotation mechanism analogous to that proposed by Westheimer for the hydrolysis of ethylene methyl phosphate. Stabilization of bidentate coordination might play a role in metal ion activation of phosphate-transfer enzymes.