Tetra-n-butylamine(carbonato-kappa O-2,O')cobalt(III)n-butylcarbamate dihydrate

The title compound, [Co(CO3)(C4H11N)4](C5H10NO2)·2H2O, is a coordination complex with an N4O2 coordination sphere around the central CoIII ion. The small bite angle of the chelating carbonate causes a distortion of the octahedral geometry to an approximately C2v local symmetry. Hydrogen-bonding between the carbonate, carbamate and amine groups, and the water of crystallization, results in a complex two-dimensional network

Triborate and pentaborate salts of non-metal cations derived from N-substituted piperazines: synthesis, structural (XRD) and thermal properties

The synthesis and characterization of a triborate salt, [H2N(CH2CH2)2NH2][B3O3(OH)4]2 (1), and four pentaborate salts, [H2N(CH2CH2)2NH][B5O6(OH)4] (2a), [MeHN(CH2CH2)2NH][B5O6(OH)4] (2b), [MeHN(CH2CH2)2NMe][B5O6(OH)4] (2c) and [Me2N(CH2CH2)2NMe2][B5O6(OH)4]2 (2d) are described. TGA and DSC analysis (in air, 25�1000 °C) indicate that triborate 1 decomposes to B2O3via a multistage process, with the first stage (<250 °C) being dehydration to condensed polymeric hexaborate of approximate composition: [H2N(CH2CH2)2NH2][B6O10]. The pentaborates (2a�2d) are thermally decomposed to B2O3via a 2 stage process involving polymeric [NMC][B5O8]. The anhydrous polyborates were amorphous. BET analysis of materials derived from the thermolysis of 1 at 250, 400, 600, and 1000 °C, were all non-porous (surface area <1.8 m2 g�1). A single-crystal X-ray diffraction study of 1 showed that it contains isolated triborate(1�) anions in a structure comprised of alternating cationic and anionic layers held together via extensive H-bonds. Single-crystal XRD structural studies on pentaborate salts 2c and 2d are also reported

Synthesis and X-ray structural studies of pentaborate(1−) salts containing substituted imidazolium cations

The preparation of [NMC][B5O6(OH)4] {NMC = 2-MeC3N2H4 (3),1-MeC3N2H4 (4), 4-MeC3N2H4 (5), 1,2-Me2C3N2H3 (6), 1,2,3-Me3C3N2H2 (7), 1-EtC3N2H4 (8), 2-EtC3N2H4 (9), 2-Et-4-MeC3N2H3 (10) 1-Et-3-MeC3N2H3 (11) and 2-iPrC3N2H4 (12)} salts are reported. Compounds were characterised by spectroscopy (NMR and IR) and by single crystal XRD (6, 7, 9, 10, 12) studies. All structures show extensive H-bonded networks and 7 displays the first example of reciprocal paired αααα anion�anion interactions. These are facilitated by the pentaborate boroxole rings being significantly distorted (boat) from the near-planar arrangements more commonly observed. The related imidazolinium salt, [2-MeC3N2H6][B5O6(OH)4] (13), has also been characterised by XRD studies. Compound 13 is isostructural with 3. Thermal properties (TGA/DSC) indicate decomposition to B2O3via [NMC][(B5O8)n] intermediates

Unexpected Polymorphism in Nitroanilines

We are currently engaged in a systematic study of solid forms, including polymorphs, co-crystals and salts, produced by simple organic molecules with weakly interacting functional groups. A Microvate[1] reaction block has been used to investigate the effects of temperature and solvent on crystallisation of polymorphs, co-crystals and salts. This allows various temperature profiles involving different rates of heating, cooling and stepped cooling to be used with a number of solvents. Slurry conversion techniques and sublimation can also be utilised. In one line of study we have attempted to make co-crystals and salts of substituted nitroanilines. In one of these experiments using 2-methyl-6-nitroaniline with organic acids we have unexpectedly obtained two as yet unreported forms of pure 2-methyl-6-nitroaniline. Form 1 crystallised in space group P21/c, a = 8.927Å, b = 11.186Å, c = 14.680Å, ? = 90°, ? = 104.79°, ? = 90° and Form 2 in space group P21/c, a = 3.925Å, b = 12.850Å, c = 14.275Å, ? = 90°, ? = 91.46°, ? = 90°. In light of these findings 2-methyl-3-nitroaniline has also been investigated and so far one pure form of the compound has been crystallised in space group P21, a = 14.012Å, b = 4.021Å, c = 15.483Å, ? = 90°, ? = 90°, ? = 90°. On the poster the structures of the crystal forms and the relationships between them will be assessed.1. www.ReactArray.co

Supramolecular Assembly: Recorded in ‘tape-form’

Supramolecular assemblies, as distinct from ‘co-ordination polymers’ generally owe their occurrence to intermolecular interactions at the medium (e.g. hydrogen-bonding) to weak (e.g. Van der Waal’s) end of the scale. Though individually explained and successfully described by theory, much still remains unknown when these interactions are placed in competition with one-another and ultimately, what the net effect of multiple contacts will confer on intermolecular geometry. It is this void that has spawned the discipline now known as crystal engineering [1] - the systematic investigation of supramolecular interactions, how they behave and the effects they cause on molecular packing motifs. As the knowledge base in this field has increased, it has given rise to the concept of the supramolecular synthon – the spatial arrangements of intermolecular interactions which play the same rôle in supramolecular synthesis as conventional synthons do in organic synthesis. More recently Desiraju [2,3] and others [4,5] have described a wide variety of supramolecular synthons which can be used to control the architecture of organic molecules. Figure 1: Tripodal interaction in the one of the supramolecular synthons under investigationIt is on the key principles of crystal engineering that the study of known and robust supramolecular synthons, found to form “tape-like” assemblies [5] [Fig. 1] have been forged. In this poster, the results of some detailed comparative studies on the careful addition of various supramolecular contacts, conditions and/or constraints to the periphery of these “tapes” will be described. These investigations have led to some interesting discoveries [6] due to their impact on the intermolecular assembly of the primary “tape-like” structure and on secondary inter-“tape” architecture

The perils of large 'small' molecules - successful refinement of metallosupramolecular grid-like assemblies

With recent advances in diffractometers and as computers grow ever more powerful, it is possible to collect and solve several data sets every day. Thus the technique is now being used as alternative form of characterisation. This also has meant that the size of crystals required to obtain data has decreased, and the size of the molecules involved has increased, which can lead to a severe shortfall in data to parameter ratio. A recent area which has gained from these advancements is that of molecular grid and tape structures, although the successful solution and refinement may often be problematic due to the generally large asymmetric units. As chemists design and prepare these larger structures, the composition is generally known, but the geometry is still vital to determine. Most programs for full structure determinations were designed for small molecules with up to 100 non-hydrogen atoms. Although they can cope with larger numbers, quite a few crash once more than 500 atoms become involved. This does cause problems not only in attempts to solve structures, but also (especially for the chemist) when trying to visualise them later. Through our work with the UK National Service it has been necessary to address some of the problems described. For example the application of focussing mirrors to a rotating anode generator significantly increases the number of observed reflections for small crystals and for those of the above type of compound which are often weakly diffracting. This increase in quantity of experimental data coupled with the large number of variables provides a real test for the software. Generally, of the initial solution refinement programs, it is often only Shelxs-97 which produces a reasonable solution, although the assignment of the atoms is tedious. Most of the 'brute-force' programs give a nonsensical solution, if at all. For refinements Shelxh-97 does work, although sometimes the source code needs to be tweaked to cope with the largest structures (4000 parameters might be ample for most systems but 8000 is often a better limit). This poster will present successful structure determination of a number of these cases and the pitfalls and method of treatment will be outlined

(1S*,4S*,5R*,8R*)-4,8-Diphenyl-3,7-dioxa- bicyclo[3.3.0] octan-2-one

The title compound, C18H16O3, (I), was prepared in the course of studies towards the synthesis of furofuran ligands and was reported previously [Brown &amp; Hinks (1998). Chem. Commun. pp. 1895-1896]. The compound is a a model system, where both oxygenated aromatic rings that are present in the natural products have been substituted by a simple phenyl group

Structural systematics of 4,4'-disubstituted benzenesulfonamidobenzenes. 1. Overview and dimer-based isostructures

One hundred 4,4'-disubstituted benzenesulfonamidobenzenes, X-C6H5-SO2-NH-C6H5-Y, where X, Y = NO2, CN, CF3, I, Br, Cl, F, H, Me, OMe, have been synthesized and their crystal structures determined. The resulting set of 133 structures, which includes polymorphic forms, is used to make a comparative study of the molecular packing and the nature of the intermolecular interactions, including the formation of hydrogen-bonding motifs and the influence of the two substituents X and Y on these features. Nine distinct supramolecular connectivity motifs of hydrogen bonding are encountered. There are 74% of all the structures investigated which exhibit one of two motifs based on N-HO=S interactions, a dimer or a chain. There are three other, infrequent motifs, also employing N-HO=S links, which exhibit more complexity. Four different chain motifs result from either N-HO=N, N-HCN or N-HOMe interactions, arising from the presence of a nitro (position Y), nitrile (X or Y) or methoxy (Y) substituent. The program XPac [Gelbrich &amp; Hursthouse (2005). CrystEngComm, 7, 324-336] was used to systematically analyse the packing relationships between crystal structures. Similar discrete (zero-dimensional) and extended (one-dimensional and two-dimensional) structure components, as well as cases of isostructurality were identified. A hierarchy for the classification of the 56 distinct structure types of this set is presented. The most common type, a series of 22 isostructures containing the simple centrosymmetric N-HO=S-bonded dimer, is discussed in detail