Preparation and solid-phase thermal deamination of the unitary, binary, and ternary tris(diamine)chromium(III) complexes

Article abstract of DOI:10.1021/ic00136a059

The unitary, binary, and ternary tris(diamine)chromium(III) complexes [Cr(aa)₃]X₃·nH₂O, [Cr(aa)₂(bb)]X₃·nH₂O, and [Cr(aa)(bb)(cc)]X₃·nH₂O were prepared and their thermal deamination was investigated both nonisothermally (derivatographically) and isothermally in the solid phase, where aa, bb, and cc are different diamines selected from ethylenediamine (en), d,l-1,2-propanediamine (pn), and 1,3-propanediamine (tn), X is chloride or thiocyanate ion, and n is a number of 0-3. The complexes obtained by the reaction were isolated and identified by means of IR and visible spectrophotometry and TLC. The diamines evolved by the deamination were captured as the hydrochlorides and identified by IR spectrophotometry. The results showed that all the chlorides evolve 1 mol of diamine to be converted into the cis-dichlorobis(diamine) complexes, whereas all the thiocyanates undergo deamination to give the trans-bis(diamine)bis(isothiocyanato) complexes. In the deamination of the binary and ternary tris(diamine) complexes, it was found that the diamine which escapes from the complexes is a diamine having the lower boiling point than other diamines contained. cis-[CrCl₂(tn)₂]Cl obtained by the deamination of [Cr(tn)₃]Cl₃·H₂O, [Cr(en)(tn)₂]Cl₃·2H₂O, and [Cr(pn)(tn)₂]Cl₃·H₂O readily isomerizes to the trans form upon subsequent heating. The order of ease of evolution of diamines in the unitary complexes was pn < en < tn, whereas that in the binary and ternary complexes was tn < pn < en which is consistent with the decreasing order of boiling points of the diamines.