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.