PREPARATION AND KINETIC STUDIES OF NEW AMMINE COMPLEXES OF CHROMIUM(III) WITH LIGANDS DIMETHYLFORMAMIDE (DMF) AND DIMETHYLSULFOXIDE (ME2SO) - KINETICS OF THE SOLVOLYSIS REACTION OF [CRH2O(NH3)5]3+ IN ME2SO AND AQUATION OF [CRME2SO(NH3)5]3+

The following new complexes have been prepared: trans(CrMe2SO)(NH3)4](ClO4)3;cis[Cr(dmf)2(NH3)4](ClO4)3;cis[Cr(Me2SO)(dmf)(NH3)4]- (ClO4)3·2H2O;[CrMe2SO(NH3)5](ClO4)3·2H2O and [CrMe2SO(NH3)5]I3. Furthermore, the following new cations have been characterized only in solution: cis[CrH2O(Me2SO)(NH3)4]3+, trans[CrH2O(Me2SO)(NH3)4]3+ and cis[CrH2O(dmf)(NH3)4]3+. The electronic spectra are recorded for all of these complexes and standard analyses lead to the sequences Cl < dmf < Me2SO < H2O in the spectrochemical series, and H2O < dmf < Me2SO < Cl in the nepheleuxetic series for Cr(III). The aquation kinetics of [CrMe2SO(NH3)5]3+ and solvolysis kinetics of [CrH2O(NH3)5]3+ in anhydrousMe2SO have been studied. With the [CrMe2SO(NH3)5]3+ complex a single process corresponding to aquation of Me2SO is observed. Kinetics studies give kaq = 3.2 × 10-4 s-1 at 49.5 °C [I = 0.10 M (HClo4)], with activation parameters ΔH‡ = 20.30 Kcal mol-1 and ΔS‡ = -11.92 cal mol-1 K-1. With the [CrH2O(NH3)5]3+ complex a single process corresponding to solvolysis of H2O is observed in anhydrous Me2SO. Kinetic studies give k = 6.10 × 10-4 s-1 at 50 °C, with activation parameters ΔH‡ = 22.74 Kcal mol-1 and ΔS‡ = -2.98 cal mol-1 K-1. © 1979.