Preparation, characterization and solid state thermal studies of cadmium(II) squarate complexes ofhane-1,2-diamine and its derivatives

Abstract

[CdL₃]C₄O₄ [L=ethane-1,2-diamine (en)], [CdL₂(H₂O)₂]C₄O₄ [L=N-methylethane-1,2-diamine (meen), N-ethylethane-1,2-diamine (eten), N-propylethane-1,2-diamine (pren), propane-1,2-diamine (pn) and N-methylpropane-1,2-diamine (ibn)] and [CdL₂(C₄O₄)] [L=N-isopropylethane-1,2-diamine (ipren)] have been synthesized by the addition of the respective diamine to finely powdered CdC₄O₄×2H₂O and their thermal studies have been carried out in the solid state. [Cd(en)₃]C₄O₂ upon heating loses two molecules of diamine in two overlapping steps yielding Cd(en)C₄O₄ which upon further heating transforms to unidentified products. The diaquabis(diamine) species, [CdL₂(H₂O)₂]C₄O₄, show thermally induced deaquation-anation reaction in the solid state and thereby produce [CdL₂(C₄O₄)], which reverts on exposure to humid atmosphere (RH =90%) for 20–24 h. All the squarato bis(diamine) species, [CdL₂(C₄O₄)], on pyrolysis in the solid state transform to unidentified products through the formation of intermediates, CdL_1.5C₄O₄, (L=meen, pren and ipren), CdLC₄O₄ (L=meen, en, pren, ipren, pn and ibn) and CdL_0.5C₄O₄ (L=eten, pn and ibn). However, amongst the intermediates only the mono diamine species, CdLC₄O₄ can be isolated in pure form and the pyrolytic process is the only way to synthesize them. The monodiamine species can be stored in a desiccator as well as in an open atmosphere and proposed to have a polymeric structure.