Definitive crystal structures of ortho-, meta- and para-carboranes: supramolecular structures directed solely by C–H⋯O hydrogen bonding to hmpa (hmpa = hexamethylphosphoramide)

Abstract

Cocrystallisation of ortho-metaand para-carboranes with hmpa (hexamethylphosphoramide) results in the isolation of 1 : 1 carborane:hmpa adducts which provide the first definitive X-ray structures of the unsubstituted carboranes as part of three very different C-H-0 hydrogen-bonded supramolecular structures.

Synthesis and Characterization of 3-Chloropropyl-substituted o- Carboranes: Crystal Structures of 1,2-(1,3-Propanediyl)-o-carborane, 1-(3-Chloropropyl)-o-carborane and 1,2-Bis(3-chloropropyl)-ocarborane

“…In the structure of 2 (Fig. 1) the cage carbon-carbon bond length is 1.628(7)Å, which is nearly the same as that in the parent o-carborane (1.629(6)/1.630(6)Å) [20]. The exo-polyhedral five-membered ring in the structure of 2 is found to be pseudo-planar with a torsion angle C1-C2-C5-C2# of 0.3(2) • , the planarity representing most probably an average of the conformations present in the crystal.…”

Self-Assembly of Grid and Helical Hydrogen-Bonded Arrays Incorporating Bowl-Shaped Receptor Sites That Bind Globular Molecules

“…C ± H groups of carboranes are acidic [12] and a limited number of supramolecular complexes have been established, notably the 1:1 complexes of o,m,p-carborane with hexamethylphosphoramide, [13] 1:1 host ± guest complexes of o-carborane with a-,b-,g-cyclodextrins and a 1:2 complex with acyclodextrin, [14] 1:1 complexes of o-carborane with diaza[18]-crown-6 and aza [18]crown-6, [15] and the 1:2 complex of ocarborane with CTV. [7] The latter complex is distinctly different with each C ± H carborane directed towards the centroid of an aromatic ring in the cavity of the CTV as a weak non-classical hydrogen bond calculated to be energetically favoured by 2.74 kcal mol…”

The electronic structure of 1,2-PCB10H11 molecular films: a precursor to a novel semiconductor

“…The high symmetry of the disordered struc ture results in only three unique bonding distances, 1.892(3), 1.8285(19) and 1.859(3)Å. Using bond distance data from the literature [25][26][27][28][29][30][31][32] obtained from less symmetric molecules, electron diffraction data or molecules co-crystallized with hy drogen bond acceptors, one can estimate approximate values for these various bonds. Averaging gives a value of 1.83 Å, close to the values found, as summarized in Table 1.…”