Thermolysis of complex cyanides—XIII Structural transformations at thermal decomposition of [M(en) 3][M′(CN) 5NO] double complexes

Abstract

[Cr(en) 3][Cr(CN) 5NO]·3H 2O and [Cr(en) 3][Mn(CN) 5NO]·3H 2O lose water at 130°C evolve three moles of ethylendiamine one mole of NO and half a mole of cyanogen between 200 and 540°C to form Cr(CN) 2, and Cr(CN) 2 and together with Mn(CN) 2, respectively. [Co(en) 3][Cr(CN) 5NO], after one mole of ethylendiamine has been lost in an endothermic process at 190°C is transformed to the intermediate trans-[Co(en) 2][Cr(CN) 3NO] in an exothermal reaction at 220°C. The structural transformation was proved by comparison of the thermal curves of cis- and trans-[Co(en) 2Cl 2]Cl, while the transfer of cyanide ligands from anion to cation has previously been demonstrated by thermal decomposition of other similar double complexes. Because of the less stable intermediate the trans effect is much weaker for [Co(en) 3][Mn(CN) 5NO]·2H 2O than in the case of [Co(en) 3][Cr(CN) 5NO].