Supramolecular assemblies of germanium(II) halides with O-, S- and Se-donor macrocycles - the effects of donor atom type upon structure

Reaction of GeCl(2)(dioxane)] with 18]aneS(6) (1,4,7,10,13,16-hexathiacyclooctadecane) gives the neutral GeCl(2)(18]aneS(6))] which forms a supramolecular sheet network involving exocyclic coordination, with the macrocycles bridging Ge atoms which are in a pseudo-trigonal bipyramidal environment from two Cl and two S atoms (saw-horse), with one lone pair assumed to occupy the remaining equatorial void. Conversely, using the mixed S/O macrocycles 18]aneS(3)O(3) (1,4,7-trithia-10,13,16-trioxacyclooctadecane) and 15]aneS(2)O(3) (1,4-dithia-7,10,13-trioxacyclopentadecane) (L) leads to the monocationic pentagonal pyramidal GeCl(L)](+) whose structures show endocyclic Ge coordination, and displacement of one Cl. The Ge-S and Ge-O bond lengths are surprisingly disparate in these two complexes, and in the former the coordinated Cl is axial, while in the latter it occupies the pentagonal plane (with an S atom axial). Cyclic selenoethers form one-dimensional or two-dimensional supramolecular assemblies with Ge(ii) halides, including GeCl(2)(8]aneSe(2))] (8]aneSe(2) = 1,5-diselenacyclooctane), (GeCl(2))(2)(16]aneSe(4))] (16]aneSe(4) = 1,5,9,13-tetraselenacyclohexadecane), GeBr(2)(16]aneSe(4))] and (GeI(2))(2)(16]aneSe(4))]·GeI(4)- these represent the first germanium species with selenoether ligation. Structural studies on each of these show exocyclic GeX(2) coordination, giving networks based upon Se(2)X(2) coordination at Ge(ii) with a distorted pseudo-trigonal bipyramidal environment in which the Ge-based lone pair is assumed to occupy the vacant equatorial vertex. Further weak GeX contacts are also evident in some cases. The weak, secondary GeS/Se and GeX interactions that pervade these systems may be regarded as a further type of supramolecular interaction allowing assembly of new network structures, and the long II contacts evident between the GeI(2) and GeI(4) units in (GeI(2))(2)(16]aneSe(4))]·GeI(4) probably provide a small thermodynamic contribution leading to co-crystallisation of ordered GeI(4) molecules within the network.