Kinetics of the thermal dehydration of trans-fluoroaquobis(ethylenediamine)chromium(III) tetracyanometallate(II) [metal(II) = Ni(II), Pd(II) and Pt(II)]

The solid phase thermal deaquation-anation of trans-[CrF(H2O)(en)2][M(CN)4] (M = Ni, Pd, Pt; en = ethylenediamine) has been investigated by means of non-isothermal DSC and isothermal and non-isothermal TG measurements. The physical model for these reactions (nucleation, growth, diffusion or intermediates) has been found by comparison of the isothermal and non-isothermal TG data for all the principal g(α) expressions (0.2≤α≤0.8) and by the shape of the isothermal curves. The values found for activation energy are low (∼ 130 kJ mol-1 for the Ni compound, ∼ 140 kJ mol-1 for the Pd compound, and ∼ 100 kJ mol-1 for the Pt compound). These data permit the assignment of the deaquation-anation mechanism of the SN1 type involving a square-base pyramid activated complex and elimination of water as Frenkel defects. © 1984.