Chromium(III) complexes in dipolar aprotic solvents. VIII. Solvolysis of hexaisothiocyanatochromate(III) and solvent exchange, substitution and anation of the pentaisothiocyanato(solvento)chrornate(III) complex, [Cr(NCS)₅(sol)]^2-

Abstract

The displacement of the coordinated Me₂SO from [Cr(NCS)₅(Me₂SO)]^2- by NCS^- and pyridine has been studied in the solvent tetramethylene sulphone (sulpholane). The results are consistent with a limiting dissociative mechanism. The solvolysis reactions:                  [Cr(NCS)₆]^3- + sol → [Cr(NCS)₅(sol)]^2- + NCS^- have been studied in the solvents (sol) Me₂SO, HCONMe₂ and MeCONMe₂. The transition states for these solvolysis reactions are compared with a dissociative model                          [Cr(NCS)₅^(3-)+(∂+)...NCS^∂-] by means of solvent transfer activity coefficients. Kinetic and activation data are recorded for a number of solvent interchange reactions:             [Cr(NCS)₅(sol₁)]^2- + sol₂ → [Cr(NCS)₅(sol₂)]^2- + sol₁