Search

Single‐crystal X‐ray diffraction studies for a variety of metal ion complexes of functionalised sarcophagines (sarcophagine=sar=3,6,10,13,16,19‐hexa‐azabicyclo[6.6.6]icosane) have further confirmed not only that the form of the metal ion/sar unit is unique for each metal, albeit with a sensitivity of the conformation to the associated counter anions, but also that for any given metal and ligand substituent, the dimensions (bond lengths and angles) of the complex and the substituent at the secondary nitrogen centres do not differ significantly from those of the isolated components. Despite this, where the substituent contains reactive sites, the reactivity differs markedly from that of their form in an uncoordinated substrate. Rationalisations are offered for these differences, in part through the use of Hirshfeld surface analysis of the intermolecular interactions. The kinetic inertness of the complexes means that the metal ions can be considered to act as regioselective protecting groups. [ABSTRACT FROM AUTHOR]

Eight organic salts made up of two different organic phosphonium monocations, tetraphenylphosphonium or benzyltriphenylphosphonium, and common anions of different shape, size and charge distribution have been structurally authenticated. The crystal packing for the tetraphenylphosphonium cations involves one-dimensional infinite stacked columns incorporating translational quadruple embraces (TQPE) regardless of the type of counter ion. As for benzyltriphenylphosphonium salts, different packing arrays were obtained with different anions. Interestingly, the anions control the intermolecular packing of the same phosphonium cation, while hydrogen bonding is found to be the dominant contributor in the overall self-assembly. Hydrophobic interactions between the phosphonium cations driven by the phenyl–phenyl embrace involving π⋯π and/or C–H⋯π interactions also contribute to the cohesion of the structures. Charge-assisted hydrogen bonding and halogen bonding were also evident, which are relatively strong compared to classical hydrogen bonds, as judged from the short intermolecular distances. The interactions have also been quantified using Hirshfeld surfaces analyses. [ABSTRACT FROM AUTHOR]

Structure determinations for some Co(III) complexes of simple derivatives of the cage hexamine 3,6,10,13,16,19-hexa-azabicyclo[6.6.6]icosane ("sarcophagine") show that there is no evidence that the H-bonding involving the NH centres of the complex cations is influenced by electronic effects due to the substituents. "H-bond chelation" of chloride anions or water molecules results in retention of the symmetrical lel3 conformation. [ABSTRACT FROM AUTHOR]

A single crystal of 3,5-di-tert-butylpyrazole has been the subject of structure determinations at 10, 100, 120 and 299 K. Above ∼ 110 K, the structure is Pbca, a ≈ 11.3, b ≈ 20.6, c ≈ 10 Å, Z = 8. Below 110 K, the c axis is doubled and the space group becomes Pb21a, Z = 16. Here the asymmetric unit is comprised of four molecules, arranged as a pair of overlapping hydrogen-bonded dimers, all components being ordered. In each case one methyl group of each t-butyl group lies coplanar with its parent pyrazole ring and, within each quasi-inversion-related dimer, one molecule has both of these methyl groups directed away from the N2 component ‘cis’, while in the other, one methyl group is toward (‘trans’). Above 110 K the four molecules collapse into one, with one t-butyl group (corresponding to an overlaid ‘cis/trans’ pair of the low-temperature form) modelled as disordered. The disorder has been previously described as ‘temperature dependent’ (Deacon et al, 2001), but the present studies suggest it to be dependent on the history of the particular specimen as well. [ABSTRACT FROM AUTHOR]

The crystal structures of the Tutton salts (NH4)2-[Cu(H2O)6(SO4)2, diammonium hexaaquacopper disulfate, formed with normal water and isotopically substituted H218O, have been determined by X-ray diffraction at 9.5 K and are very similar, with Cu-O(7) the longest of the Cu-O bonds of the Jahn-Teller distorted octahedral [Cu(H2O) 6]2+ complex. It is known that structural differences accompany deuteration of (NH4)2[Cu(H2O) 6](SO4)2, the most dramatic of which is a switch to Cu-O(8) as the longest such bond. The present result suggest that the structural differences are associated with hydrogen-bonding effects rather than with increased mass of the water ligands affecting the Jahn-Teller coupling. The Jahn-Teller distortions and hydrogen-bonding contacts in the compounds are compared with those reported for other Tutton salts at ambient and high pressure. [ABSTRACT FROM AUTHOR]

Structurally authenticated complexes of the cone-shaped p -sulfonatocalix[4]arene and conformationally flexible p -sulfonatocalix[6]arene devoid of co-ligands/ancillary molecules are limited. Early and late members of the lanthanide series as their trivalent ions, La3+, Er3+, and Yb3+, form complexes from aqueous media under these conditions. For La3+ and Er3+, distinct hydrophobic and hydrophilic bilayers are formed with p -sulfonatocalix[4]arene, whereas for Yb3+, two complexes form that deviate from the well-known bilayer arrangement of calixarenes. Replacing the calixarene with p -sulfonatocalix[6]arene results in a hydrogen-bonded network with alternating hydrophobic–hydrophilic layers associated with primary coordination of Yb3+, with the larger macrocyclic calixarene in a partial cone conformation. Bilayers are created when cone-shaped p -sulfonatocalix[4]arene forms complexes with La3+ and Er3+, whereas with Yb3+ overall assembly deviates from the bilayer arrangement. With conformational flexible p -sulfonatocalix[6]arene, this results in a hydrogen bonded network with alternating hydrophobic-hydrophilic layers associated with primary coordination of Yb3+, with the calixarene crystallised in a partial cone conformation. [ABSTRACT FROM AUTHOR]

The crystal structure of hexa­carbonyl­chromium(0), [Cr(CO)6], has been refined with an accurate and extensive X-ray data set collected at 11 K. This data set should be suitable for charge-density analysis studies. The structure is made up of isolated Cr(CO)6 mol­ecules of very near octahedral symmetry, containing a crystallographic mirror plane. [ABSTRACT FROM AUTHOR]