Indium(iii) {2}-metallacryptates assembled from 2,6-dipicolinoyl-bis(N,N-diethylthiourea)

Abstract

Reactions of 2,6-dipicolinoylbis(N,N-diethylthiourea), H₂L^py, InCl₃, MCl salts (M = Rb⁺, K⁺, Na⁺ or NH₄⁺) and NEt₃ in methanol give cationic {2}-metallacryptates of the composition [M⊂{In₂(L^py)₃}]⁺ (M⁺ = Rb⁺, K⁺, Na⁺ or NH₄⁺). They can be isolated as PF₆⁻ salts. The structural characterization of the products by means of spectroscopic methods and X-ray crystallography reveals host–guest assemblies, in which a monovalent guest cation M⁺ is encapsulated in the cryptand-like host compound {In₂(L^py)₃}. The host–guest directional interactions are coordination or hydrogen bonds depending on the nature of the guest cation. A ¹⁵N NMR spectroscopic study on the inclusion compound with ¹⁵NH₄⁺ cations reveals a dynamic structure of the corresponding {2}-metallacryptate in solution and partial exchange of the ammonium ions by coordinating solvents.