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

Reaction of [GeCl2(dioxane)] with [18]aneS(6) (1,4,7,10,13,16-hexathiacyclooctadecane) gives the neutral [GeCl2([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-trioxacycloocta-decane) 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 [GeCl2([8]aneSe(2))] ([8]aneSe(2) = 1,5-diselenacyclooctane), [(GeCl2)(2)([16]aneSe(4))] ([16]aneSe(4) = 1,5,9,13-tetraselenacyclohexadecane), [GeBr2([16]aneSe(4))] and [(GeI2)(2)([16]aneSe(4))]center dot GeI4 - these represent the first germanium species with selenoether ligation. Structural studies on each of these show exocyclic GeX2 coordination, giving networks based upon Se2X2 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 Ge center dot center dot center dot X contacts are also evident in some cases. The weak, secondary Ge center dot center dot center dot S/Se and Ge center dot center dot center dot X interactions that pervade these systems may be regarded as a further type of supramolecular interaction allowing assembly of new network structures, and the long I center dot center dot center dot I contacts evident between the GeI2 and GeI4 units in [(GeI2)(2)([16]aneSe(4))]center dot GeI4 probably provide a small thermodynamic contribution leading to co-crystallisation of ordered GeI4 molecules within the network.