Base Hydrolysis of Coordinated Trimethyl Phosphate

The novel metal complex ions pentaammine ( trimethyl phosphate)- rhodium(III) and -iridium(III) have been synthesized and their hydrolysis in basic solution studied. The hydrolyses yield coordinated dimethyl phosphate ( dmp ), exclusively for the iridium complex, but accompanied by metal-oxygen bond rupture in the case of the rhodium complex. The reaction of the iridium complex proceeds with phosphorus-oxygen cleavage. The hydrolyses in the absence of nucleophiles other than hydroxide obey simple rate laws, v = k1[(NH3)5Ir( tmp )][OH-] for the iridium complex and v = (k1 + k2[OH-])[(NH3)5Rh( tmp )] for rhodium. Both complexes hydrolyse to yield coordinated dmp approximately 400 times faster than the analogous reaction for uncoordinated tmp. In butylamine -buffered solutions of [(NH3)5Rh( tmp )]3+, N- methylated butylamine is produced presumably as a result of nucleophilic attack of butylamine at a carbon centre of coordinated trimethyl phosphate.