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N-alkylated C2-symmetric amino acid amide derivatives were shown to catalyse the Michael addition of 2-hydroxy-1,4-napthoquinone to β-nitrostyrene, achieving a maximum ee of 44%. The corresponding trifluoroacetic acid salts also catalysed the aldol reaction between 4-nitrobenzaldehyde and hydroxyacetone, leading to the formation of predominantly syn-aldol products in up to 55% ee. Aspects of the solvent dependence of the aldol reaction and the H-bonding of the catalyst were investigated.

In this paper, the clean high yielding, synthesis, and structure of the tetraphosphine ligand, 1,1′,2,2′-tetrakis-(di-isopropyl-phosphino)ferrocene, (tdipf), is described. In addition, improved synthesis methods for 1,1′,2,2′-tetrakis(diphenylphosphino)ferrocene, (tppf), and 2,2′-bis-(diphenylphosphino)-1,1′-dibromoferrocene are also reported, and the synthetic method is generalised to include the synthesis of 3,3′-bis-(diphenylphosphino)-1,1′,2,2′-tetrabromoferrocene. The related ligands 2,2′-bis-(iso-propylphosphino)-1,1′-bis-diphenylphosphinoferrocene (diprdppf) and 2,2′-bis-(di-isopropylphosphino)-dibromoferrocene have also been prepared and characterised. The crystal structure of the square planar bimetallic nickel (II) dichloride of tdipf is also described, together with a brief NMR study investigating the synthesis of this and related metal complexes. The crystal structures of the palladium and platinum dichloride complexes of 2,2′-bis-(di-isopropylphosphino)-1,1′-dibromoferrocene, bpdbf, are also discussed in the context of comparison with previously known crystal structures in the same general family. A general discussion on the synthetic methodology is given, along with indications for future research that other researchers might explore.

Several tetrahydroxidohexaoxidopentaborate(1-) salts of N-substituted diimidazolium cations or N-substituted dipyrrolidinium cations linked through N-C6-N chains have been synthesized and characterized spectroscopically (NMR, IR) and by single-crystal XRD studies: [R(NC3H3N)(CH2)6(NC3H3N)R][B5O6(OH)4]2·xH2O (R = Me, x = 0 (1); R = Et, x = 3 (2); [Me(NC3H3N)(CH2(C6H4)CH2)(NC3H3N)Me][B5O6(OH)4]2 (3), [(C4H8N)(R)(CH2)6(R)(NC4H8)][B5O6(OH)4]2·xB(OH)3 (R = Me, x = 0 (4, two polymorphs); R = Et, x = 0 (5); R = Bu, x = 4 (6); R = allyl, x = 0 (7)). Representative samples (1 and 7) were also characterized by thermal (TGA/DSC) studies; compounds are thermally decomposed to B2O3 in air. Numerous anion-anion H-bonding interactions are present in the solid-state structures of 1–5 and 7 as giant anionic networks. Unusually, in 6 there are no R22(8) anion-anion interactions as the co-crystallized B(OH)3 bridges between all pentaborate anions. H-bonding interactions in 1–7 have been examined using Etter graph set analysis; C(8), C33(18), R22(8), R22(12) and R44(12) motifs have been identified.

The self-assembly and self-organization of water molecules are relevant in many fields of research. When water spontaneously reacts with 2,2,6,6-tetramethylpiperidine (TMP) to form colourless and crystalline discrete needles, only in the exact ratio of 2:1, it is important to understand the phenomenon. Single-crystal X-ray and neutron diffraction data have unveiled that TMP self-assembles around columns of water molecules, and as such, the resulting adduct may be described as a series of molecular water pipes.

During the racemization of a novel pharmaceutical spirocyclic imidazole–amine compound, namely, 6′-bromo-N-(6′-bromo-4-methoxy-4′′-methyl-3′H-dispiro[cyclohexane-1,2′-indene-1′,2′′-imidazol]-5′′-yl)-4-methoxy-4′′-methyl-3′H-dispiro[cyclohexane-1,2′-indene-1′,2′′-imidazol]-5′′-imine, C36H41Br2N5O2, two impurities were isolated. These impurities were clearly dimers from mass spectroscopic analysis, however single-crystal diffraction characterization was required for the assignment of stereochemistry. The single-crystal diffraction results revealed subtly different structures to those proposed, due to an unexpected proton transfer. The dimers contain four stereocentres, but two of primary interest, and are centrosymmetric, so after careful structure refinement and close inspection it was possible to unambiguously assign the stereochemistry of both the homochiral [(S),(S)- and (R),(R)-] and the heterochiral [(S),(R)- and (R),(S)-] compounds.

Two substituted phosphonium tetrahydoxidohexaoxidopentaborate(1-) salts, [iPrPPh3][B5O6(OH)4]·3.5H2O (1) and [MePPh3][B5O6(OH)4]·B(OH)3·0.5H2O (2), were prepared by templated self-assembly processes with good yields by crystallization from basic methanolic aqueous solutions primed with B(OH)3 and the appropriate phosphonium cation. Salts 1 and 2 were characterized by spectroscopic (NMR and IR) and thermal (TGA/DSC) analysis. Salts 1 and 2 were thermally decomposed in air at 800 °C to glassy solids via the anhydrous phosphonium polyborates that are formed at lower temperatures (2/g. Rhe recrystallization of 1 and 2 from aqueous solution afforded crystals suitable for single-crystal XRD analyses. The structure of 1 comprises alternating cationic/anionic layers with the H2O/pentaborate(1-) planes held together by H-bonds. The cationic planes have offset face-to-face (off) and vertex-to-face (vf) aromatic ring interactions with the iPr groups oriented towards the pentaborate(1-)/H2O layers. The anionic lattice in 2 is expanded by the inclusion of B(OH)3 molecules to accommodate the large cations; this results in the formation of a stacked pentaborate(1-)/B(OH)3 structure with channels occupied by the cations. The cations within the channels have vf, ef (edge-to-face), and off phenyl embraces. Both H-bonding and phenyl embrace interactions are important in stabilizing these two solid-state structures.

The synthesis and characterization of six new substituted guanidium tetrahydroxidohexaoxidopentaborate(1-) salts are reported: [C(NH2)2(NHMe)][B5O6(OH)4]·H2O (1), [C(NH2)2(NH{NH2})][B5O6(OH)4] (2), [C(NH2)2(NMe2)][B5O6(OH)4] (3), [C(NH2)(NMe2)2][B5O6(OH)4] (4), [C(NHMe)(NMe2)2][B5O6(OH)4]·B(OH)3 (5), and [TBDH][B5O6(OH)4] (6) (TBD = 1,5,7-triazabicyclo [4.4.0]dec-5-ene). Compounds 1–6 were prepared as crystalline salts from basic aqueous solution via self-assembly processes from B(OH)3 and the appropriate substituted cation. Compounds 1–6 were characterized by spectroscopic (NMR and IR) and by single-crystal XRD studies. A thermal (TGA) analysis on compounds 1–3 and 6 demonstrated that they thermally decomposed via a multistage process to B2O3 at >650 °C. The low temperature stage (2O. Reactant stoichiometry, solid-state packing, and H-bonding interactions are all important in assembling these structures. An analysis of H-bonding motifs in known unsubstituted guanidinium salts [C(NH2)3]2[B4O5(OH)4]·2H2O, [C(NH2)3][B5O6(OH)4]·H2O, and [C(NH2)3]3[B9O12(OH)6] and in compounds 1–6 revealed that two important H-bonding R22(8) motifs competed to stabilize the observed structures. The guanidinium cation formed charge-assisted pincer cation–anion H-bonded rings as a major motif in [C(NH2)3]2[B4O5(OH)4]·2H2O and [C(NH2)3]3[B9O12(OH)6], whereas the anion–anion ring motif was dominant in [C(NH2)3][B5O6(OH)4]·H2O and in compounds 1–6. This behaviour was consistent with the stoichiometry of the salt and packing effects also strongly influencing their solid-state structures.

Traditionally small-molecule crystallographers have not usually observed or recognized significant radiation damage to their samples during diffraction experiments. However, the increased flux densities provided by third-generation synchrotrons have resulted in increasing numbers of observations of this phenomenon. The diversity of types of small-molecule systems means it is not yet possible to propose a general mechanism for their radiation-induced sample decay, however characterization of the effects will permit attempts to understand and mitigate it. Here, systematic experiments are reported on the effects that sample temperature and beam attenuation have on radiation damage progression, allowing qualitative and quantitative assessment of their impact on crystals of a small-molecule test sample. To allow inter-comparison of different measurements, radiation-damage metrics (diffraction-intensity decline, resolution fall-off, scaling B-factor increase) are plotted against the absorbed dose. For ease-of-dose calculations, the software developed for protein crystallography, RADDOSE-3D, has been modified for use in small-molecule crystallography. It is intended that these initial experiments will assist in establishing protocols for small-molecule crystallographers to optimize the diffraction signal from their samples prior to the onset of the deleterious effects of radiation damage.

Several oxidoborates, self-assembled from B(OH)3 and templated by cationic Ni(II) coordination compounds, were synthesized by crystallization from aqueous solution. These include the ionic compounds trans-[Ni(NH3)4(H2O)2][B4O5(OH)4].H2O (1), s-[Ni(dien)2][B5O6(OH)4]2 (dien = N-(2-aminoethyl)-1,2-ethanediamine (2), trans-[Ni(dmen)2(H2O)2] [B5O6(OH)4]2.2H2O (dmen = N,N-dimethyl-1,2-diaminoethane) (3), [Ni(HEen)2][B5O6(OH)4]2 (HEen = N-(2-hydroxyethyl)-1,2-diaminoethane) (4), [Ni(AEN)][B5O6(OH)4].H2O (AEN = 1-(3-azapropyl) -2,4-dimethyl-1,5,8-triazaocta-2,4-dienato(1-)) (5), trans-[Ni(dach)2(H2O)2][Ni(dach)2] [B7O9(OH)5]2.4H2O (dach = 1,2-diaminocyclohexane) (6), and the neutral species trans-[Ni(en)(H2O)2{B6O7(OH)6}].H2O (7) (en = 1,2-diaminoethane), and [Ni(dmen)(H2O){B6O7(OH)6}].5H2O (8). Compounds 1–8 were characterized by single-crystal XRD studies and by IR spectroscopy and 2, 4–7 were also characterized by thermal (TGA/DSC) methods and powder XDR studies. The solid-state structures of all compounds show extensive stabilizing H-bond interactions, important for their formation, and also display a range of gross structural features: 1 has an insular tetraborate(2-) anion, 2–5 have insular pentaborate(1-) anions, 6 has an insular heptaborate(2-) anion (‘O+’ isomer), whilst 7 and 8 have hexaborate(2-) anions directly coordinated to their Ni(II) centers, as bidentate or tridentate ligands, respectively. The Ni(II) centers are either octahedral (1–4, 7, 8) or square-planar (5), and compound 6 has both octahedral and square-planar metal geometries present within the structure as a double salt. Magnetic susceptibility measurements were undertaken on all compounds.

The Lucite Alpha process is the predominant technology for the preparation of acrylics. This two-stage process involves the palladium-catalysed formation of methyl propanoate from ethene, CO, and methanol, followed by the oxidative formylation of methyl propanoate into methyl methacrylate. A range of bis-1,2-disubstituted aminomethylferrocenes has been prepared and characterised. These complexes serve as precursors to a variety of bulky ferrocenylmethyldiphosphanes that, in turn, function as ligands in the palladium-catalysed process. We describe the crystal structures of five ligand precursors and provide a rationale for their design. In situ catalyst testing on palladium complexes derived from ferrocenylphosphanes demonstrates that these are highly selective (>99.5%) catalysts for the formation of methyl propanoate from ethene, CO, and methanol and have turnover numbers exceeding 50,000. This article credits those researchers who worked on this project in the early days, who received little or no credit for their achievements and endeavours.

Two novel salts containing the anion [Ni(mnt)2]− (mnt = maleonitriledithiolate) have been synthesized. The counter-ions, [Fe(II)(L1 or L2)2], are cationic complexes where L1 and L2 are methylated derivatives of 2,6-bis(pyazolyl)pyridine or pyrazine, which are similar to ligands found in a series of spin-crossover (SCO) complexes. Both salts are characterized by variable temperature single crystal X-ray diffraction and bulk magnetization measurements. Compound 1, [Fe(II)(L1)2][Ni(mnt)2]2 displays an incomplete and gradual SCO up to 300 K, followed by a more rapid increase in the high-spin fraction between 300 and 350 K. Compound 2, [Fe(II)(L2)2][Ni(mnt)2]2.MeNO2, shows a gradual, but more complete SCO response centered at 250 K. For compound 2, the SCO is confirmed by variable temperature Mössbauer spectroscopy. In both cases, the anionic moieties are isolated from each other and so no electrical conductivity is observed.

The development of organic electronics calls for low-cost printing techniques that can prepare high quality, large-area organic single crystals. Here, Rigaset al. achieve this goal by combining spray printing and antisolvent crystallization and test the method on various materials and substrates.

Artificial light-harvesting systems cannot self-assemble into photon-capturing structures that can reversibly switch into an inactive state. Here, the authors describe a simple and robust dipeptide construct which self-assembles to fibrils, platelets or nanospheres with varying optical properties.

The synthesis of a number of pentaborate(1-) salts from cations arising from N-substituted α,α-, α,β-, and α,γ-diaminoalkanes has been attempted in aqueous solution from B(OH)3 and the appropriate diammine in a 10:1 ratio. Despite relatively mild work-up conditions the pentaborate(1-) salts prepared were not always as anticipated and the following compounds were isolated in good yield: [Me2NH(CH2)2NHMe2][B5O6(OH)4]2 (1), [Et2NH(CH2)2NHEt2][B5O6(OH)4]2 (2), [Et2NH2][B5O6(OH)4] (3), [Me2NH2][B5O6(OH)4] (4), [Me2NH(CH2)3NHMe2][B5O6(OH)4]2 (5), [Et2NH(CH2)3NHEt2][B5O6(OH)4]2 (6), [Me3NCH2CH=CH2][B5O6(OH)4] (7), and [Me3N(CH2)3NMe3] [B5O6(OH)4]2.0.5H2O (8). The tetraborate(2-) salt, [Me3N(CH2)2NMe3][B4O5(OH)4].2B(OH)3.2H2O (9) was obtained in moderate yield (41%) from a 3:1 reaction of B(OH)3 with [Me3N(CH2)2NMe3](OH)2. All compounds were characterized by spectroscopy (1H, 11B, 13C NMR and IR) and thermal gravimetric analysis (TGA). BET analysis on materials derived thermally from selected samples (1, 2, 6, 7) all had porosities of < 1 m2/g, demonstrating that they were non-porous. Single-crystal XRD structures were obtained for 2, 3, 7, 8 and 9 and all contain extensive H-bonded polyborate lattices.

Two zinc(II) hexaborate(2−) complexes, [Zn{κ3O-B6O7(OH)6}(κ3N-dien)]·0.5H2O (dien = NH(CH2CH2NH2)2) (1) and (NH4)2[Zn{κ2O-B6O7(OH)6}2(H2O)2]·2H2O (2), and a zinc(II) dodecaborate(6−) complex, (1,3-pnH2)3[(κ1N-H3N{CH2}3NH2)Zn{κ3O-B12O18(OH)6}]2·14H2O (1,3-pn = 1,3-diaminopropane) (3), have been synthesized and characterized by single-crystal XRD studies. The complexes crystallized through self-assembly processes, from aqueous solutions containing 10:1 ratios of B(OH)3 and appropriate Zn(II) amine complex: [Zn(dien)2](OH)2, [Zn(NH3)4](OH)2, and [Zn(pn)3](OH)2. The hexaborate(2−) anions in 1 and 2 are coordinated to octahedral Zn(II) centres as tridentate (1) or bidentate ligands (2) and the dodecaborate(6−) ligand in 3 is tridentate to a tetrahedral Zn(II) centre.

The synthesis and characterization by single-crystal X-ray diffraction (XRD) studies of two new zinc(II) hexaborate(2−) complexes, [Zn(en){B6O7(OH)6}]·2H2O (en = 1,2-diaminoethane) (1) and [Zn(pn){B6O7(OH)6}]·1.5H2O (pn = 1,2-diaminopropane) (2), are reported. These complexes crystallize from aqueous solutions containing 10:1 ratios of B(OH)3 and the appropriate Zn(II) amine complexes ([Zn(en)3][OH]2 or [Zn(pn)3][OH]2) through self-assembly processes. The hexaborate(2−) anions in 1 and 2 are coordinated to two Zn(II) centers and form one-dimensional (1-D) polymeric coordination chains. R22(8) and R22(6) inter-chain H-bond interactions play an important role in these self-assembly processes and are discussed.

In the title compound, C20H14N2O2, the hydroxybenzene ring is almost perpendicular to the mean plane of the naphthalene ring system, making a dihedral angle of 85.56 (4)°. The 4H-pyran ring fused with the naphthalene ring system has a flattened boat conformation. In the crystal, O—H...N and N—H...O hydrogen bonds link the molecules into a supramolecular layer in the bc plane; N—H...π interactions also contribute to this arrangement. The layers are linked by weak by C—H...π and π–π [inter-centroid separation = 3.8713 (7) Å] interactions.

In the title compound, C16H12N2O3, the chromene ring system is nearly planar [maximum deviation from the mean plane = 0.057 (1) Å], and is almost perpendicular to the benzene ring, with a dihedral angle of 85.29 (5)°. In the crystal, molecules are linked by classical N—H...O, O—H...O and O—H...N hydrogen bonds, and weak C—H...O hydrogen bonds, forming a three-dimensional supramolecular network. Furthermore, a weak π–π stacking interaction is observed; the centroid-to-centroid distance is 3.7260 (7) Å.

In the title compound, C21H16N2O2, the methoxybenzene ring is almost perpendicular to the mean plane of the naphthalene ring system, making a dihedral angle of 83.62 (5)°. The 4H-pyran ring fused with the naphthalene ring system is almost planar [maximum deviation = 0.033 (1) Å]. In the crystal, molecules are linked into inversion dimers by pairs of N—H...N hydrogen bonds. N—H...O hydrogen bonds connect the dimers, forming a helical supramolecular chain along the a-axis direction. The crystal packing also features C—H...π interactions.

In the title compound, C20H13ClN2O, the chlorobenzene ring is almost perpendicular to the mean plane of the naphthalene ring system, making a dihedral angle of 81.26 (8)°. The 4H-pyran ring fused with the naphthalene ring system has a flattened boat conformation. In the crystal, N—H...N hydrogen bonds generate chains along the b-axis direction. Further N—H...N hydrogen bonds link these chains into sheets parallel to (010). The crystal packing also features C—H...π interactions. The crystal studied was an inversion twin with a 0.557 (16):0.443 (16) domain ratio.

In the title compound, C20H14N2O, the plane of the phenyl ring is almost normal to that of the naphthalene ring system, forming a dihedral angle of 83.15 (8)°. The 4H-pyran ring fused with the naphthalene ring system has a flattened boat conformation. In the crystal, molecules are linked by pairs of N—H...N hydrogen bonds, forming inversion dimers with an R22(12) ring motif. The dimers are connected by C—H...π interactions, forming supramolecular chains along [010].

In the title compound, C16H14O4, the benzene rings are inclined at a dihedral angle of 75.14 (9)°. The torsion angle of the bridging O—C—C—O group is −76.50 (11)°. In the crystal, molecules are linked by C—H...O hydrogen bonds, forming C(6) chains along [100]. Furthermore, C—H...π interactions and π–π stacking interactions [centroid–centroid distances = 3.6957 (7) and 3.6735 (8) Å] contribute to the stability of the crystal packing.

In the title compound, C12H7N3OS, the five-membered 1,3-thiazolidine ring is nearly planar [maximum deviation = 0.032 (2) Å] and makes a dihedral angle of 84.14 (9)° with the phenyl ring. In the crystal, molecules are linked by C—H...N hydrogen bonds into infinite chains along [-101]. C—H...π interactions contribute to the arrangement of the molecules into layers parallel to (101).

In the title compound, C14H13N3O2S, the dihedral angle between the thiophene and phenyl rings is 24.95 (8)°. The molecular structure is consolidated by intramolecular N—H...O and C—H...S interactions. The crystal structure features N—H...N and N—H...O hydrogen bonds forming centrosymmetric R22(12) dimers, which are linked into a two-dimensional network parallel to (011) with an S(6)R22S(6) motif. In addition, π–π stacking interactions [centroid–centroid distance = 3.7013 (12) Å] occur between the thiophene and phenyl rings of adjacent molecules.

In the title compound, C19H17NO2, the dihedral angle between the benzene ring and the naphthalene ring system is 9.72 (5)°, while the torsion angle of the C—N—C—C bridging group is 179.24 (17)°. The methyl group of the 1-phenylethanol moiety is disordered over two positions with a refined occupancy ratio of 0.775 (5):0.225 (5). The molecular conformation is stabilized by an intramolecular N—H...O hydrogen bond, which generates an S(6) ring motif. In the crystal, molecules are linked by O—H...O hydrogen bonds, forming zigzag chains propagating along the c-axis direction. Neighbouring chains are linked via C—H...O interactions, forming a two-dimensional slab-like network parallel to the bc plane.

The molecular conformation of the title compound, C13H8BrFN2O3, is essentially planar, with maximum deviations of 0.076 (1) and −0.080 (2) Å for the O atoms of the NO2 group. The molecular conformation is stabilized by an intramolecular O—H...N hydrogen bond, forming an S(6) ring motif. In the crystal, pairs of molecules are linked via two pairs of C—H...O hydrogen bonds, forming inversion dimers that enclose R22(7)R22(10)R22(7) ring motifs.

In the title molecule, C14H15NO3, the ring system is essentially planar, with an r.m.s. deviation of 0.003 Å. The atoms of the ethane-1,2-diol group were refined as disordered over two sets of sites in a ratio of 0.815 (3):0.185 (3). The molecular conformation is stabilized in part by an intramolecular N—H...O hydrogen bond, which forms an S(6) ring. In the crystal, molecules are connected by N—H...O and O—H...O hydrogen bonds, forming a two-dimensional network parallel to (100). The network also features weak C—H...O hydrogen bonds. Weak C—H...π interactions also observed.

In the title compound, C21H21BrClNO4, the dihydropyridine ring adopts a flattened boat conformation. The 3-bromo-5-chloro-2-hydroxyphenyl ring forms a dihedral angles of 84.44 (7)° with the dihydropyridine mean plane. The molecular conformation is stabilized by an intramolecular O—H...O hydrogen bond, with an S(8) ring motif. In the crystal, O—H...O and C—H...O hydrogen bonds link the molecules, forming a three-dimensional network.

The title compound, C20H23BrN2O2, containing an ibuprofen core, crystallizes with three independent molecules of similar conformation in the asymmetric unit. In these three molecules, the two benzene rings make dihedral angles of 82.7 (2), 71.2 (2) and 78.0 (3)° with respect to each other. The atoms of the isobutyl groups in two of the molecules are disordered over two positions, with site-occupancy ratios of 0.516 (8):0.484 (8) and 0.580 (8):0.420 (8). In the crystal, molecules are linked by N—H...O, C—H...O and O—H...N hydrogen bonds. Furthermore, C—H...π interactions are also observed.

In the title compound, C21H24N4O2, inversion-related molecules are linked into dimers through pairs of N—H...O hydrogen bonds, which generate R22(8) motifs. As well as dimer formation, an additional N—H...O hydrogen bond and two C—H...π contacts, involving H atoms from the phenyl ring and the pyrrole and benzene rings of the indole system, generate a three-dimensional network.

In the title compound, C21H20N2O4, the naphthalene ring system makes a dihedral angle of 84.5 (3)° with the benzene ring, and the –C(=O)–N(H)–N(H)–C(=O)– torsion angle is 70.7 (7)°, so that the molecule is twisted. An S(6) ring motif is formed via an intramolecular O—H...O hydrogen bond. In the crystal, molecules are linked by N—H...O and C–H...O hydrogen bonds into supramolecular layers in the ab plane.

The piperidine ring of the title compound, C16H15N5, adopts a chair conformation. The pyridine ring is essentially planar, with a maximum deviation of 0.035 (3) Å. The pyrrole and pyridine rings are almost coplanar, forming a dihedral angle of 3.48 (14)°. In the crystal, no classical hydrogen bonds were found. In the crystal, the molecules are linked by aromatic π–π stacking [centroid–centroid separations = 3.4984 (16) and 3.9641 (15) Å between pyrrole and pyridine rings and between pyridine rings, respectively].

In the title compound, C15H13N5O, the morpholine ring adopts a chair conformation. The dihedral angle between the pyrrole ring and the pyridine ring is 28.93 (14)°. In the crystal, the molecules are linked by C—H...O hydrogen bonds occur, and aromatic weak π–π stacking [centroid–centroid separation = 4.178 (2) Å] and C—H...π interactions consolidate the packing.

In the title compound, C13H12N4S, an amino N atom is connected to a 1,3-benzothiazole fused-ring system and a dimethyl-substituted pyrimidine ring, these components being aligned [interplanar dihedral angle = 1.9 (1)°]. The secondary amino N atom forms an intermolecular N—H...N hydrogen bond to an N atom of the fused ring of an adjacent molecule, generating a centrosymmetric cyclic hydrogen-bonded dimer [graph set R22(8)].

In the title compound, C8H9N4S−·C2H3O2−, the cation is essentially planar (r.m.s deviation = 0.037 Å) with the guanidine unit bent out of the plane of the fused-ring system by 4.6 (3)°. In the asymmetric unit, the cations and anions are linked into R22(8) motifs. In the crystal, further N—H...O and N—H...N hydrogen bonds link the components into a two-dimensional network.

The non-H atoms of the cation of the title salt, C8H9N4S+·Cl−, are approximately co-planar (r.m.s. deviation = 0.037 Å), with one amino group forming an intramolecular hydrogen bond to the tertiary N atom of the benzothiazole fused-ring system. The cations and anions are linked by cyclic R21(6) N—H...Cl hydrogen-bonding associations, generating helical chains running along the b-axis direction.

The structure of the title salt, C24H20P+·H8B3−, at 120 (2) K has triclinic (P1) symmetry with an unusual Z = 5, although there is pseudosymmetry observedwith the tetraphenylphosphonium cations exhibiting Ioverline4 symmetry. One of the anions is disordered over two sets of sites with refined occupancies of 0.478 (11) and 0.522 (11).

The title compound, C36H30NP2+·I−, was obtained accidently from crystallization of a reaction mixture containing [(Ph3P)2N]OH and B(OH)3, which was contaminated with MeI. There are two independent [(Ph3P)2N]+ cations and two I− anions within the asymmetric unit. The central PNP angles are non-linear [137.6 (2) and 134.4 (2)°] and the phenyl substituents on P centres adopt different conformations within these two cations.