The vibrational spectra of the copper(II) formates: Part IV. The thermal behaviour of Cu(HCOO) 2 · 4H 2O and Cu(HCOO) 2 · 2H 2O

Abstract

Several modifications of Cu(HCOO) 2 exist and two, or possibly three, are characterized in the present study by means of Raman measurements. Upon the dehydration of Cu(HCOO) 2 · 4H 2O, monoclinic Cu(HCOO) 2 is formed in a topotactical reaction and a Raman study reveals that the environments around the copper and formate ions are very similar in the two compounds. No evidence can be found of the formation of the dihydrate by means of the dehydration of the tetrahydrate, even though DTA/TG measurements show that the dehydration process is complex and occurs in several steps. When monoclinic Cu(HCOO) 2 is further heated it transforms into orthorhombic Cu(HCOO) 2 below 100°C. The dehydration of the dihydrate results in the formation of a modification of Cu(HCOO) 2 which closely resembles the monoclinic modification but behaves differently upon further application of heat.