Kinetics and mechanism of aquation of [Cr(NCS)(edtrp)]-, [Cr(NCS)(R-pdtrp)]-, [Cr(edtrp)(NCSHg)]+ and [Cr(R-pdtrp) (NCSHg)]+ complexes. Unexpected rate retardation in strongly acidic media for NCS- ligand release

Three new complex ions, [Cr(NCS)(R-pdtrp)]^-, [Cr(R-pdtrp)(NCSHg)]⁺ and [Cr(edtrp)(NCSHg)]⁺, that are derivatives of the trans-equatorial isomers of [Cr(R-pdtrp)(H₂O)]⁰ and [Cr(edtrp)(H₂O)]⁰ (edtrp= ethylenediamine-N,N,N-tripropionate, R-pdtrp= R-propane-1,2-diamine-N,N,N-tripropionate) have been obtained and characterized in solution. Rate constants and activation parameters, including, in two cases, volumes of activation, have been determined. Rate retardation for NCS^- ligand release has been observed with increasing acidity within the pH 0–2 range. The mechanism of the reactions has been discussed.