A cobalt(II) complex with ethylenediamine inside zeolite A

Abstract

Reaction of the partially dehydrated cobalt(II)-exchanged zeolite A (Co-A) with ethylenediamine (en) at 130 C in an autoclave yields after 24 h a product (Coen-A) in which entire Co(II) content (tetrahedrally coordinated in the partially dehydrated Co-A) is present in the form of the Co(en)3(2+) ions. Steric factors require the Co(en)3(2+) ions to be substituted only in the larger cages of zeolite A (alfa-cages), implying that the conversion of Co-A into Coen-A is accompanied by a migration of Co2+ ions initially located in the smaller cages (beta-cages) into alfa-cages. The Co/en molar ratio in Coen-A is 1:5.6, so that a fraction of en is also present in a noncoordinated form. IR spectral data suggest that the coordinated en adopts to the gauche conformation. TG analysis shows that the thermal decomposition of Coen-A occurs in four steps, such that water is lost first, followed by the loss of en.