Intercalation and co-ordination of ammonia and 1,2-diaminoethane into cobalt(II)-, nickel(II)-, copper(II)-, and vanadium(IV)-exchanged α-tin phosphate

Abstract

The reactions of gaseous ammonia and 1,2-diaminoethane (en) with α-SnM(PO₄)₂·H₂O (M = Co²⁺, Ni²⁺, Cu²⁺, or VO²⁺) have been investigated. Reactions occur with retention of the layered phosphate structure, the NH₃-containing materials giving rise to an interlayer separation of 10.0 ± 0.05 Å. Co-ordination of NH₃ occurs in all cases except for VO²⁺(as deduced from electronic absorption spectra); Co²⁺ is present in a tetrahedral, probably CoN₃O, environment not found in classical co-ordination chemistry, presumably as a consequence of the restricted space available in the interlayer. Ammonia co-ordinates to Ni²⁺ to give a cis-octahedral NiN₃O₃ environment and for Cu²⁺ a tetragonal octahedral environment, probably CuN₂O₂O′₂. An extensive surface and interlayer complex chemistry is displayed by low (2%) loaded Cu²⁺-exchanged materials, for which e.s.r. studies have been made. The layer structure is retained on heating to 110 °C, stability to loss of ammonia being in the order: Cu²⁺ > Co²⁺ > Ni²⁺, with the greatest change in geometry for the partially dehydrated products occurring in the case of Ni²⁺ which adopts a five-co-ordinate environment. 1,2-Diaminoethane co-ordinates to both Cu²⁺ and Co²⁺, although only as a monodentate ligand; it does not appear to co-ordinate to either Ni²⁺ or VO²⁺, instead showing a tendency to hydrogen-bond to phosphate groups in the interlayer.