A new copper(II) chelate complex with polyamines as fire retardant and epoxy hardener: Synthesis, crystal and electronic structure, and thermal behavior of (ethylenediamine-N,N′)-(diethylenetriamine-N,N′,N″)-copper(II) hexafluoridosilicate

Abstract

A new (ethylenediamine-N,N′)-(diethylenetriamine-N,N′,N″)-copper(II) hexafluoridosilicate complex, [Cu(eda)(deta)]SiF6 (1) (eda – ethylenediamine; deta – diethylenetriamine), was synthesized by direct interaction of anhydrous CuSiF6 with polyethylenepolyamine (pepa – H2N[C2H4NH]nH, where n = 1 (eda) and 2 (deta)). The crystals of 1 were characterized by IR spectroscopy and X-ray diffraction. Compound 1 consists of SiF62− discrete anions and [Cu(eda)(deta)]2+ complex cations whose Cu2+ ions are chelated by eda and deta. The coordination polyhedron of Cu(II) atom is an elongated square pyramid which consists of four nitrogen atoms belonging to NH2 groups of eda and NH2 and NH groups of deta at the base of the pyramid and of one more nitrogen atom from NH2 group of deta at its apical position. Ab initio quantum-chemical calculations of chelation process were carried out for 1 by the restricted Hartree-Fock method using a 6-31G∗ basis set. The influence of the chelate complex 1 upon its fire retardant properties was analyzed. The calculated electron-stereo-chemical parameters for 1 are in a good agreement with its thermal parameters investigated by differential thermal analysis. The thermal decomposition of 1 is finished off at 368 °C and the maximal combustion temperature of gaseous decomposition products is 544 °C. Keywords: Copper(II) chelate complexes, Synthesis, Crystal structure, Electron-molecular structure, Differential thermal analysis