ABSTRACT Upon addition of carbon monoxide (CO) to a solution of (k-N, C, N-2, 6-bis(diethylaminomethyl)-phenyl)methyl platinum(II),[NCN]PtMe,(1), a ligand arm is displaced to form [SP-4-2] ((k-N,C-2,6-bis(diethylaminomethyl)-phenyl) carbonmethyl platinum(II), N[CN]Pt(CO)(Me),(2). Addition of CO to a THF solution of 2 results in the formation of [SP-4-3]((k-N,C-2,6-bis(diethylaminomethyl)-phenyl)acylcarbonyl platinum(II),N[CN]pt(Ac)(CO),(3). In THF ,2 partially isomerizes in the presence of CO to form [SP-4-4]((k-N,C-2,6-bis(diethylaminomethyl)-phenyl)carbonylmethyl platinum(II), N[CN]Pt(Me)(CO).(2’).in equilibrium with 2(K=ca.2 at 100 degree celcius). In the absence of CO, only trace isomerization was observed. Thermolysis of 3 results in the formation of 2 and 2’ , while a reaction of 3 with trimethylamine N-oxide results exclusively in the formation of 2. Both three and five-coordinate intermediates have been shown to be accessible ,leading to two proposed mechanisms for the thermolysis of 3 and the microscopic reverse of this reaction.