Hector, Andrew L., Levason, William, Webster, Michael, Reid, Gillian and Zhang, Wenjian (2011) Supramolecular assemblies of germanium(ii) halides with O-, S- and Se-donor macrocycles – the effects of donor atom type upon structure. Dalton Transactions, 40 (3), 694-700. (doi:10.1039/c0dt00749h). (PMID:21116584)
Abstract
Reaction of [GeCl2(dioxane)] with [18]aneS6 (1,4,7,10,13,16-hexathiacyclooctadecane) gives the neutral [GeCl2([18]aneS6)] 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]aneS3O3 (1,4,7-trithia-10,13,16-trioxacyclooctadecane) and [15]aneS2O3 (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]aneSe2)] ([8]aneSe2 = 1,5-diselenacyclooctane), [(GeCl2)2([16]aneSe4)] ([16]aneSe4 = 1,5,9,13-tetraselenacyclohexadecane), [GeBr2([16]aneSe4)] and [(GeI2)2([16]aneSe4)]·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 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 GeI2 and GeI4 units in [(GeI2)2([16]aneSe4)]·GeI4 probably provide a small thermodynamic contribution leading to co-crystallisation of ordered GeI4 molecules within the network
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