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Aqueous aluminum(III) solutions at medium pH are used for industrial applications such as cement adjuvants. The necessary high Al3+ concentrations are achieved by using complexing ligands, such as lactic acid, to prevent precipitation. Here, we grew crystals from commercially available neutralized aluminum lactate solutions to derive an understanding of the underlying aluminum lactate chemistry. Using X-ray diffraction in combination with multinuclear NMR spectroscopy and quantum mechanical calculations, we found that the crystals have a stoichiometry of Na3[Al(l-lactate)3]2·6H2O and consist of negatively charged [Al(l-lactate)3]23– bis-clusters. The remarkable stability of these clusters is achieved by linking both Al(l-lactate)3 subunits via three very short symmetrical hydrogen bonds between the α-hydroxy groups with half of them being deprotonated. The trends for both the 27Al chemical shift and the spin–spin relaxation for the Lohtragon-type solutions as a function of pH suggest the bis-cluster to be...

Iron(II) coordination polymers with an N2O2 coordinating Schiff base-like equatorial ligand bearing different alkyl chain lengths (C16, C18, C20, and C22) and 1,2-bis(4-pyridyl)ethyne, 1,2-bis(4-pyridyl)ethene or 1,2-bis(4-pyridyl)ethane as bridging ligand are synthesized. All complexes display a rather similar abrupt spin transition above room temperature, which is investigated using magnetic measurements and Mossbauer spectroscopy. Variation of the bridging ligand and the alkyl chain lengths allows fine tuning of the transition temperature in the range between 338 K and 357 K. Single crystal X-ray structure analysis of two coordination polymers and one of the starting complexes reveals the formation of a lipid layer-like arrangement of the amphiphilic complexes in all cases. Further characterization by thermal gravimetric analysis, differential scanning calorimetry, X-ray powder diffraction, and polarized optical microscopy show in all cases solid–solid phase transitions. Those transitions determine the spin crossover behavior and depend on the crystal packing that is controlled by the alkyl chains in the outer periphery of the ligand. Thus, with the presented system the spin crossover properties are controlled by small alterations of the ligand structures. With respect to technological applications, spin coating is shown to be suitable for the processing of the complexes as thin films and furthermore thin platelets of the complexes can be generated by delamination techniques.

The C≡C bonds of various alkynylgermanes [Cl(H)Ge(C≡C–R1)2, Cl2Ge(C≡C–R1)2 with R1 = nBu, SiMe3, and Ge(C≡C–R1)4 with R1 = SiMe3] undergo 1,1-carboboration when treated with an excess of triethylborane at 80–110 °C. All pure final products with R1 = SiMe3 possess germole-derived structures. Intermediates and side products as a result of lost stereoselectivity of the 1,1-carboborations could be detected and in some cases identified by NMR spectroscopic studies of the reaction solutions.

The synthesis and characterization of a new class of ansa bis(indenyl) complexes of zirconium and hafnium is described. Two indenyl moieties are linked at the 1-,1′-positions via a 1,2-bis(dimethylsilyl)benzene unit. The ligand precursor was prepared via three reaction steps including Grignard coupling of chlorodimethylsilane and 1,2-dibromobenzene, PdCl2-catalyzed chlorination, and the reaction with indenyllithium. The zirconium and hafnium complexes were obtained by deprotonation of the corresponding bis-(indenyl) compound with n-BuLi followed by metalation reactions of MCl4 (M = Zr, Hf) in tetrahydrofuran. The solid state molecular structures of both complexes were established by single crystal X-ray diffraction analyses. In ethylene polymerization reactions, both complexes exhibited high activities. The zirconocene catalyst 4 showed a higher activity (7610 kg PE/mol cat. h) compared to the hafnium catalyst 5 (3590 kg PE/mol cat. h).

A so far structurally unknown polymorph (form II) of dihydrogenhydrazinium (hydrazine) sulfate(IV) was isolated as macroscopic single crystals and its structure was determined and refined as twin from single-crystal X-ray data collected at 173 K [cell parameters: a = 5.5592(11) A, b = 7.3571(15) A, c = 10.270(2) A, β = 96.75(3)°, V = 416.21(15) A3, space group P21/c]. The structure shows some similarities to the structure of the known form I: Both form II and I share zigzag shaped strands of [SO4]2– ions running along the a axes. Within both forms the strands are separated by trans type (staggered) [N2H6]2+ ions. The spatial orientation is, however, different in both forms. Consequently, distinct hydrogen bond networks are formed. The new form II was proven to be metastable and converts into form I within one day as monitored with powder X-ray diffraction (PXRD).

In an attempt to improve the electronic conductivity an FeII-rich brittle mica, a near end-member Ferro-Kinoshitalite (BaFe3Si2Al2O10F2) was synthesized via a melt approach. The structure is of 1M polytype [a = 5.4013(11) A, b = 9.3659(19) A, c = 9.987(2) A, β = 100.52(3)°, C2/m] and the iron content clearly exceeds natural abundance levels. The crystal structure is discussed with respect to established limits of isomorphous substitution based on geometrical considerations and is compared to other iron-rich micas. It is evidenced that the limitation of octahedral FeII substitution in micas is not merely governed by the misfit of tetrahedral and octahedral sheets as indicated in the literature. The electronic conductivity of contacted single crystals (μS·cm–1) is comparable to the conductivity of Ferrous-Tainiolite and is unfortunately not enhanced by the increased iron content. It is determined by the valence state of Fe rather than by the total Fe content.

An assessment is undertaken for the formation of anorthite crystalline phase in a melilite-based glass composition (CMAS: 38.7CaO–9.7MgO–12.9Al2O3–38.7SiO2 mol %), used as a sealing material in solid oxide fuel cells, in view of the detrimental effect of anorthite on the sealing properties. Several advanced characterization techniques are employed to assess the material after prolonged heat treatment, including neutron powder diffraction (ND), X-ray powder diffraction (XRD), 29Si and 27Al magic-angle spinning nuclear magnetic resonance (MAS-NMR), and in situ Raman spectroscopy. ND, 29Si MAS-NMR, and 27Al MAS-NMR results revealed that both Si and Al adopt tetrahedral coordination and participate in the formation of the network structure. In situ XRD measurements for the CMAS glass demonstrate the thermal stability of the glass structure up to 850 °C. Further heat treatment up to 900 °C initiates the precipitation of melilite, a solid solution of akermanite/gehlenite crystalline phase. Qualitative XRD data for glass-ceramics (GCs) produced after heat treatment at 850 °C for 500 h revealed the presence of anorthite along with the melilite crystalline phase. Rietveld refinement of XRD data indicated a high fraction of glassy phase (∼67%) after the formation of crystalline phases. The 29Si MAS-NMR spectra for the CMAS-GC suggest the presence of structural units in the remaining glassy phase with a polymerization degree higher than dimer units, whereas the 27Al MAS-NMR spectra revealed that most Al3+ cations exhibit a 4-fold coordination. In situ Raman spectroscopy data indicate that the formation of anorthite crystalline phase initiated after 240 h of heat treatment at 850 °C owing to the interaction between the gehlenite crystals and the remaining glassy phase.

The structure of the commercial polymorph (form II) of 5-amino-2,3-dihydro-1,4-phthalazinedione (luminol) used for ages by crime scene investigators to secure blood evidence was determined by powder X-ray diffraction and Rietveld refinement. The “new” form II is a polytype1 of form I.2 The two polymorphs only differ in distinct π-stacking motifs. Slurry experiments prove that the commercial material is indeed the metastable polymorph.

2,2-Dimethyl-5-(triphenylphosphoranylidene)acetyl-1,3-dioxan-4,6-dione (3) is a new activated β-ketoacyl equivalent, readily prepared in quantitative yield by reaction of Meldrum’s acid with the stable ylide Ph3PCCO. Its reaction with α-amino esters affords the corresponding N-(β-ketoacyl)amino ester ylides which, when treated with aldehydes and KOtBu, undergo a simultaneous Wittig olefination cum Dieckmann cyclisation to yield the respective 3-enoyltetramic acids.

Aluminosilicate glasses are considered to follow the Al-avoidance principle, which states that Al–O–Al linkages are energetically less favorable, such that, if there is a possibility for Si–O–Al linkages to occur in a glass composition, Al–O–Al linkages are not formed. The current paper shows that breaching of the Al-avoidance principle is essential for understanding the distribution of network-forming AlO4 and SiO4 structural units in alkaline-earth aluminosilicate glasses. The present study proposes a new modified random network (NMRN) model, which accepts Al–O–Al linkages for aluminosilicate glasses. The NMRN model consists of two regions, a network structure region (NS-Region) composed of well-separated homonuclear and heteronuclear framework species and a channel region (C-Region) of nonbridging oxygens (NBOs) and nonframework cations. The NMRN model accounts for the structural changes and devitrification behavior of aluminosilicate glasses. A parent Ca- and Al-rich melilite-based CaO–MgO–Al2O3–SiO2 ...

Experimental and calculated [B3LYP/6-311+G(d,p) level of theory] NMR parameters [chemical shifts δ11B and δ13C, and coupling constants 1J(13C,11B) and 1J(11B,11B)] of hexaethyl-2,4-dicarba-nido-hexaborane(8), hexaethyl-2,3,5-tricarba-nido-hexaborane(7) and their monoanions are reported. The solid-state structure of the 2,3,5-tricarbaborane was determined by X-ray crystallography as the Au–PPh3 complex, where the gold atom is linked to C5 (88 %) with contacts to B4,6 or to C2,3 (12 %) with contacts to B4,6. The 2,3,5-tricarbaborate anion η5-coordinates to the Rh(CO)2 fragment, forming a closo cluster.

A so far unknown third polymorph (form III) of 5-amino-2, 3-dihydro-1, 4-phthalazinedione (luminolate) monosodium salt could be isolated phase pure and its structure was determined by powder X-ray diffraction and Rietveld refinement [cell parameters: a = 8.0364(2) A, b = 3.69765(5) A, c = 26.4246(7) A, β = 96.346(2)°, V = 780.42(3) A3, space group P21/c]. The new structure shows many similarities to the structure of the known form II and the consequently slim differences in the diffraction traces could have easily been overlooked. Slurry experiments prove the new form to be more stable than form II. Both form II and form III crystallize in a lamellar structure. The layers are in turn built by shifted π-stacked strands of hydrogen bonded luminolate dimers. The strands are canted by ± 25° in respect to the layers. While in form II the tilt direction alternates from strand to strand within a single layer, in form III all strands within a layer are tilted in the same direction and the orientation rather alternates between adjacent layers.

We report an expeditious, iodine-catalysed oxidation of 2,3-dihydrowogonin to negletein which comprises a Wessely–Moser rearrangement (WMR), associated not with an O-demethylation, as usual, but with an oxygen to oxygen methyl shift. In contrast, DDQ in 1,4-dioxane oxidised 2,3-dihydrowogonin to wogonin without rearrangements.

Bisquinolizidine alkaloids are characterized by a chiral bispidine core (3,7-diazabicyclo[3.3.1]nonane) to which combinations of an α,N-fused 2-pyridone, an endo- or exo-α,N-annulated piperidin(on)e, and an exo-allyl substituent are attached. We developed a modular "inside-out" approach that permits access to most members of this class. Its applicability was proven in the asymmetric synthesis of 21 natural bisquinolizidine alkaloids, among them more than ten first enantioselective total syntheses. Key steps are the first successful preparation of both enantiomers of C2 -symmetric 2,6-dioxobispidine by desymmetrization of a 2,4,6,8-tetraoxo precursor, the construction of the α,N-fused 2-pyridone by using an enamine-bromoacrylic acid strategy, and the installation of endo- or, optionally, exo-annulated piperidin(on)es.

We report the syntheses of combretastatins D-2 and D-4 as well as a formal synthesis of combretastatin D-1 by a conceptually new route harnessing a ring-contracting flash vacuum pyrolytic extrusion of sulfur dioxide from the respective 16-membered sulfone precursors. Via flash vacuum pyrolysis, even metaparacyclophanes as small and strained as the hitherto unknown oxa[1.5]metaparacyclophane could be prepared as a side product en route to combretastatin D-2 by synchronous extrusion of SO2 and CO2. Postprint

Alkynyl(ferrocenyl)vinylsilanes containing up to three alkynyl units were prepared and treated with 9-borabicyclo[3.3.1]nonane (9-BBN). All reactions proceeded in the beginning by regioselective 1,2-hydroboration of the vinyl group, with boron attached to the terminal carbon. This was followed by intra-molecular 1,1-carboboration, leading to fused silacarbacycles, depending on the number of C≡C bonds. Thus, new siloles and even fused siloles became available. The solution-state structures were revealed by multinuclear NMR techniques (1H, 11B, 13C, 29Si NMR), complemented by calculated single-molecule structures and calculated NMR parameters at the B3LYP/6-311+G(d,p) level of theory. In one case, the solid-state structure of a bicyclic derivative was determined.

The resistance of metal-organic frameworks towards water is a very critical issue concerning their practical use. Recently, it was shown for microporous MOFs that the water stability could be increased by introducing hydrophobic pendant groups. Here, we demonstrate a remarkable stabilisation of the mesoporous MOF Al-MIL-101-NH2 by postsynthetic modification with phenyl isocyanate. In this process 86 % of the amino groups were converted into phenylurea units. As a consequence, the long-term stability of Al-MIL-101-URPh in liquid water could be extended beyond a week. In water saturated atmospheres Al-MIL-101-URPh decomposed at least 12-times slower than the unfunctionalised analogue. To study the underlying processes both materials were characterised by Ar, N2 and H2 O sorption measurements, powder X-ray diffraction, thermogravimetric and chemical analysis as well as solid-state NMR and IR spectroscopy. Postsynthetic modification decreased the BET equivalent surface area from 3363 to 1555 m(2) g(-1) for Al-MIL-101-URPh and reduced the mean diameters of the mesopores by 0.6 nm without degrading the structure significantly and reducing thermal stability. In spite of similar water uptake capacities, the relative humidity-dependent uptake of Al-MIL-101-URPh is slowed and occurs at higher relative humidity values. In combination with (1) H-(27) Al D-HMQC NMR spectroscopy experiments this favours a shielding mechanism of the Al clusters by the pendant phenyl groups and rules out pore blocking.

When “recrystallizing” the commercial flame retardant melaminium orthophosphate, surprisingly a hydrate with a diverging stoichiometry of melaminium (M) and phosphate (P) was obtained (M3P2·4H2O). The structure of M3P2·4H2O was solved by single-crystal X-ray diffraction analysis. The arrangement of positive melaminium and negative phosphate layers found in the crystal structure allows for both electrostatic attraction and hydrogen bonding networks. The melaminium layers are comprised of hydrogen-bonded ribbons of melaminium, which in turn are connected by π–π interactions into layers. The negatively charged phosphate layers are comprised of hydrogen bonded dihydrogenphosphate dimers and hydrogenphosphate dimers, which in turn are interconnected by direct and water-mediated hydrogen bonding into layers.

2-R-1,3,2-Diselenaphospholanes (R = iPr, Ph) with an annelated 1,2-dicarba-closo-dodecaborane(12) unit were treated with Lewis acids such as borane reagents (BH3 in THF, and BH3–SMe2) as well as Cp*-rhodium and -iridium dichloride (Cp* = pentamethylcyclopentadienyl). In all cases, the adduct formation in the beginning was followed by ring expansion through insertion of the borane or Cp*MCl2 into one of the P–Se bonds accompanied by transfer of a hydrido or chlorido ligand to phosphorus. Finally, the P–R unit was displaced from the ring to give the exchange products, in which the boron or the metal had become part of the five-membered rings. The reactions were monitored by NMR spectroscopy (1H, 11B, 13C, 31P, and 77Se). The proposed reaction sequences were found to be in agreement with calculated [B3LYP/6-311+G(d,p), LANL2DZ (Rh, Ir) level of theory] relative energies of optimized gas-phase structures of the various products. The novel molecular structure of the preferred insertion product with M = Ir, R = iPr was determined by X-ray analysis.

The most efficient strategies for the synthesis of novel 1,3dichalcogeno-2-phospholanes (chalcogen E = O, S, Se, Te) are introduced, starting from 1,2-dicarba-closo-dodecaborane(12) ("ortho-carborane"), its 1,2-di-lithiated derivative, and various phosphorus halides. The annelation of the phospholane ring with the rigid three-dimensional carborane framework causes markedly different properties when compared with other phospholanes. Most noteworthy are the structural alternatives concerning the orientation of the lone pair of electrons at phosphorus, the instability of Phalides in particular for E = O, and the pronounced tendency for dimerization in the case of P-organo derivatives, which increases from E = Te < Se < S << O. The latter is a consequence of spatial proximity between P-R or electron density at phosphorus and the carborane skeleton. Direct structural evidence is provided for monomers and dimers by single crystal X-ray structural analysis. The solution-state structures follow from consistent sets of multinuclear magnetic resonance data ( 1 H, 11 B, 13 C, 31 P, 77 Se, 125 Te NMR). This is complemented by calculations leading to optimized gas-phase geometries at the B3LYP/6-311+G(d,p) level of theory. Most NMR parameters (chemical shifts δ and indirect nuclear spinspin coupling constants n J) are calculated at the same level of theory. These studies indicate that there are cases, for which important features of the solid-state structures may not be retained in solution.

The exchange reactions of phosphorus dihalides RPX2 [R = iPr, cyclohexyl (Cy), tBu, (3,5-Me2-C6H3)CH2, Ph; X = Cl, Br], EtOPCl2, Et2NPCl2, Cl2PCH2PCl2, and Cl2PCH2CH2PCl2 with 2,2-dimethyl-4,5-[1,2-dicarba-closo-dodecaborano(12)]-1,3-diselena-2-silacyclopentane provide a straightforward route to 1,3,2-diselenaphospholanes. Some tellurium analogues were prepared from the dilithium salt [1,2-(LiTe)2-1,2-C2B10H10] and were more difficult to characterize. For the selenium compounds, some of the P-organosubstituted five-membered rings dimerize to give ten-membered rings, most readily with the more bulky alkyl groups such as tBu. This was not observed for the tellurium compounds. The conformations of the five-membered rings were studied by NMR spectroscopy and DFT methods. Striking structural differences were clear for the 2-phenyl-1,3,2-diselenaphospholane derivative in solution and in the solid state. All reactions were monitored by multinuclear magnetic resonance spectroscopy (1H, 11B, 13C, 31P, 77Se, and 125Te NMR), and solution-state structures could be proposed. Remarkably large secondary isotope effects as isotope-induced chemical shifts 2Δ12/13C(31P) exerted by the carborane carbon atoms were observed; this is apparently a special property of the five-membered ring. The gas-phase structures were optimized by DFT methods [B3LYP/6-311+G(d,p) level of theory], and the NMR parameters were calculated. Two 1,3,2-diselenaphospholanes and one dimer were characterized by X-ray analysis.

The sensing properties for resistive oxygen sensors of BaFe1-xTaxO3-δ (BFT) were investigated as a function of the Tantalum content x (0.2 ≤ x ≤ 0.7). Bulk samples were produced by using the mixed-oxide route. X-ray diffraction pattern showed that the perovskite structure was obtained and no second phases were found up to x = 0.5. The electrical conductivity of sintered samples was determined in an oxygen concentration between 1% and 100% in a wide temperature range between 400 and 900 °C. Samples between x = 0.2 and 0.4 are p-type conducting perovskite oxides with almost zero thermal activation. The range, at which the temperature dependency is absolutely zero, shifts with x from 450 °C for x = 0.2 to about 800 to 900 °C for x = 0.4. Specimens of BaFe0.7Ta0.3O3-δ revealed the lowest overall temperature dependency in the entire temperature range. All samples up to x = 0.4 responded fast and reversibly to oxygen concentration changes, even at 400 °C.

1,3,2-Diselenaphospholanes with an annelated dicarba- closo -dodecaborane(12) unit are slowly oxidized, except of the phosphorus halides, by addition of sulfur without side reaction. The analogous reaction with selenium, also slow, is accompanied either by uncontrolled decomposition or by insertion of selenium into P–Se bonds to give novel seven-membered rings containing two μ-Se 2 units. All products are characterized by multinuclear magnetic resonance methods ( 1 H, 11 B, 13 C, 31 P, 77 Se NMR spectroscopy), supported by calculations on the B3LYP/6-311+G(d,p) level of theory, and the molecular structure of one example of a 1,2,4,5-tetraselena-3-phospha heterocycle was determined by X-ray crystallography.

By using 1,2-hydroxy-1,2-dicarba-closo-dodecaborane(12) and the corresponding dilithium salt [1,2-(LiO)2-1,2-C2B10H10] for the synthesis of 1,3,2-dioxaphospholanes, it was shown that these species are short-lived with few exceptions. The phosphorus halides undergo disproportionation reactions towards phosphite derivatives, whereas the P-organo-substituted five-membered rings dimerize to give ten-membered rings. Even the P-diethylamino and the P-ethoxy compounds dimerize slowly. Dimerization is the favored process when using the dilithium salt together with ether. The reactions were monitored by multinuclear magnetic resonance spectroscopy (1H, 11B, 13C, 31P NMR). The gas-phase structures were optimized by DFT methods [B3LYP/6-311+G(d,p) level of theory], and NMR spectroscopic parameters were calculated. One dimer was characterized by X-ray analysis. All products were found to be sensitive to hydrolysis and oxidation. Thus, crystals of 1-[(1,1-dimethylethyl)hydroxyphosphinyl]oxy-2-hydroxy-1,2-dicarba-closo-dodecaborane(12) could be isolated and characterized by X-ray analysis, as well as the starting material 1,2-hydroxy-1,2-dicarba-closo-dodecaborane(12) (with HNEt2/HCl). In all three solid-state structures, the C–C(carborane) bond lengths are elongated with respect to all other neutral ortho-carborane derivatives bearing second-row substituents at one or both carbon atoms.

In the pharmaceutical industry many new active pharmaceutical ingredients (APIs) are marketed as carboxylic salts because of enhanced solubility and dissolution rates. These salts are, however, often hard to crystallize and/or exhibit a low degree of crystallinity. The reason may be found in the largely differing sizes of small inorganic cations and large organic anions in conjunction with the 1:1 stoichiometry, which makes it difficult to satisfy the coordination needs of the cations. Even rather small amphiphilic molecules like the widely used preservatives sodium benzoate (NaBz) and potassium benzoate (KBz) suffer of the same obstacle to crystallization. Both of these industrial products are marketed in semi-crystalline forms and no crystal structures were known up to now despite their industrial relevance. By applying long term annealing at 420 °C for 5 months we obtained tiny needle-like crystals of NaBz, which were nevertheless suitable for single crystal structure determination. Interestingly, the number of symmetry independent units in the crystal structure is exceptionally high (Z′ = 5), reflecting the difficulties in satisfying the coordination. Moreover, the small amphiphilic molecule undergoes a microphase separation into tubes with a hydrophilic core and a hydrophobic corona made up by the phenyl moieties. The tubes are arranged into a distorted hexagonal dense packing. Such microphases are well established with surfactants and block-copolymers, and it seems that even small amphiphilic molecules follow the same modes of crystallization. Interestingly, simply by changing the cation to KBz a competing microphase structure is realized. KBz crystallizes in a lamellar arrangement.

The thiosulfate-intercalated layered double hydroxide of Zn and Al undergoes reversible hydration with a variation in the relative humidity of the ambient. The hydrated and dehydrated phases, which represent the end members of the hydration cycle, both adopt the structure of the 3R1 polytype. In the intermediate range of relative humidity values (40–60%), the hydrated and dehydrated phases coexist. The end members of the hydration cycle adopt the structure of the same polytype, and vary only in their basal spacings. This points to the possibility that all the intermediate phases have a kinetic origin.

Two cyclic alkyl(aryl)boranes, a 1-bora-indane derivative 1, and a tricyclic derivative 4, containing the boron atom in a six-membered ring, were structurally characterized by NMR techniques in solution. The solid-state structure of the 1-bora-indane 1 was determined by X-ray crystallography. The reactivity of these cyclic alkyl(aryl)boranes towards monoalkynyltin compounds, Me3Sn-C≡C-Me and Me3Sn-C C-Fc (Fc=ferrocenyl), was studied using multinuclear magnetic resonance methods (1H, 11B, 13C, 119Sn NMR). Novel alkenylboranes were formed by 1,1-carboboration reactions. This process involves an expansion of both five- and six-membered rings. Insertion into the respective B-C(aryl) bond was preferred with high selectivity. In the case of the six-membered ring in 4, the ring expansion to seven-membered rings proved to be readily reversible, and the thermodynamically stable reaction products were formed by ring contraction and concomitant transfer of the exocyclic B-nPr group

A sodium brittle mica with the ideal composition [Na4]inter[Mg6]oct[Si4Al4]tetO20F4 was synthesized via melt synthesis in a gas tight crucible. This mica is unusual inasmuch as the known mica structure holds only room for two interlayer cations per unit cell and inasmuch as it readily hydrates despite the high layer charge while ordinary micas and brittle micas are non-swelling. The crystal structure of one-layer hydrate sodium brittle mica was determined and refined from single crystal X-ray data. Interlayer cations reside at the center of the distorted hexagonal cavities and are coordinated by the three inner basal oxygen atoms. The coordination of the interlayer cation is completed by three interlayer water molecules residing at the center of the interlayer region. The relative position of adjacent 2:1-layers thus is fixed by these octahedrally coordinated interlayer cations. Pseudo-symmetry leads to extensive twinning. In total five twin operations generate the same environment for the interlayer species and are energetically degenerate.

In the pharmaceutical industry many new active pharmaceutical ingredients (APIs) are marketed as carboxylic salts because of enhanced solubility and dissolution rates. These salts are, however, often hard to crystallise and/or exhibit a low degree of crystallinity. The reason may be the largely differing sizes of cation and anion. One way out of the resulting “coordination dilemma“ is the formation of co-crystals of the salt with its neutral acid which delivers additional coordination sites for the cation. In this line, the crystal structure of a new co-crystal of benzoic acid (HBz) and lithium benzoate (LiBz) with composition 1HBz·1LiBz was determined and was compared to published ionic co-crystals of other alkali salts with respect to the structure determining criteria: coordination number of the cation, ratio of HBz:Bz–, mode of coordination of the carboxylic groups (mono- or bidentate), and connectivity (edge- or corner-sharing) between neighbouring polyhedra. The new crystal structure is closely related to form A of 2HBz·1NaBz. Both crystal structures contain dimers with shared edges which are further connected by bridging bidentate ligands to tapes.

A simple route towards highly crystalline and hierarchically porous tungsten oxide nanotubes is presented. Interestingly, due to the limited wall thickness, the metastable orthorhombic high-temperature polymorph could be stabilized for the first time at room temperature without doping. In brief, ammonium metatungstate (AMT) is grafted over core-crosslinked poly(butadiene)-block-poly(2-vinylpyridine) (PB-b-P2VP) nanorods at pH 3. Coulomb interactions between protonated PB-b-P2VP nanorods (pKa 4.5) and metatungstate anions promote hybrid formation. Subsequent calcination of the PB-b-P2VP–AMT hybrid material at 490 °C results in a non-woven structure of hierarchically porous and crystalline, orthorhombic tungsten oxide nanotubes as confirmed by electron microscopy, X-ray diffraction, and nitrogen physisorption.

A novel tricyclic bispidine ligand is prepared and successfully applied as a chiral ligand in Cu-catalyzed asymmetric Henry reactions.

Insertion of tellurium into C–Li bonds of dilithiated 1,2-dicarba-closo-dodecaborane(12) gave 1,2-dicarba-closo-dodecaborano(12)-1,2-ditellurolate [(1,2-C2B10H10)Te2Li2](Et2O) which, after reaction with 1,2-dichlorotetramethyldisilane, afforded a six-membered heterocycle containing the Te–Si–Si–Te unit with an annelated carborane moiety, characterized by multinuclear magnetic resonance and X-ray structural analysis. As a byproduct, a five-membered ring containing a Si–Si–Te unit was formed, which was obtained as a major product, using conditions favouring partial insertion of tellurium into C–Li bonds. Treatment of [(1,2-C2B10H10)Te2Li2](Et2O) with dichlorodimethylsilane led to a five-membered heterocycle as a major product containing a Te–Te–Si unit. Various decomposition/hydrolysis/oxidation products could be identified by multinuclear magnetic resonance, among them most notably 1,2-di(hydrotelluro)-1,2-dicarba-closo-dodecaborane(12).

Acetate-intercalated layered double hydroxides (LDHs) of Ni and Al undergo reversible hydration in the solid state in response to the ambient humidity. The LDH with a high layer charge (0.33/formula unit) undergoes facile hydration in a single step, whereas the LDH with a lower layer charge (0.24/formula unit) exhibits an ordered interstratified intermediate, comprising the hydrated and dehydrated layers stacked alternatively. This phase, also known as the staged S-2 phase, coexists with the end members suggesting the existence of a solution-type equilibrium between the S-2 phase and the end members of the hydration cycle. These LDHs also undergo facile aqueous exfoliation into 2–5 nm-thick tactoids with a radial dimension of 0.2–0.5 μm.

Various alkynes have been inserted selectively and stepwise into the B–Se bond(s) of 1,3,2-diselenaboracyclopentanes {as the 4,5-[1,2-dicarba-closo-dodecaborano(12)] derivatives}. The B-phenyl derivative was much less reactive than the B-halogeno derivatives. The proposed structures were confirmed in solution by multinuclear NMR studies (1H, 11B, 13C and 77Se NMR), also supported by DFT calculations of the gas-phase molecular geometries and NMR parameters [B3LYP/6-311+G(d,p) level of theory]. Isotope-induced nuclear shielding 2Δ10/11B(13C) across weak intramolecular coordinative Se–B bonding was observed in the 13C NMR spectra of the nine-membered-ring compounds. The molecular structures of two nine-membered-ring structures with B–Cl and B–Br functions were determined by X-ray diffraction. In addition, it was shown that the slow hydrolysis of these boron halides afforded the corresponding diboroxanes and borinic acids, the structures of the former being determined by X-ray diffraction.

Exchange reactions of 2,2-dimethyl-4,5-[1,2-dicarba-closo-dodecaborano(12)]-1,3-diselena-2-silacyclopentane with phosphorus trihalides PX3 (X = Cl, Br, I) led to the corresponding phospholanes in high yield. The solid-state structure of the iodide was determined by X-ray crystallography. Treatment of the bromide with nBu3SnH afforded the parent phosphane. The reaction of the iodide with LiAlH4 in [D8]toluene proceeded very slowly and mainly gave the deuterated phosphane. All products were characterised in solution by multinuclear magnetic resonance methods (1H, 13C, 31P and 77Se NMR). Molecular gas-phase geometries were optimised at the B3LYP/6-311+G(d,p) level of theory, and NMR parameters were calculated.

Non-cyclic and cyclic silyl-substituted 1, 2-dicarba-closo-dodecaborane(12) derivatives were prepared mainly by salt elimination methods. Several known and new compounds were structurally characterized by X-ray analysis in the solid state and by mulinuclear magnetic resonance (1H, 11B, 13C, 29Si, 77Se, and 125Te NMR) in solution. This includes the 1, 2-bis(trimethylsilyl) and 1, 2-bis(chlorodimethylsilyl) derivatives as examples for non-cyclic compounds and a series of 1, 1, 3, 3-tetramethyl-4, 5-[1, 2-dicarba-closo-dodecaborano(12)]-1, 3-disila-2-element-cyclopentanes (element = S, Se, Te). Numerous spin-spin coupling constants were determined together with their signs. Molecular gas phase geometries for most compounds studied were optimized by calculations [B3Lyp/6-311+G(d, p)], and NMR parameters were calculated at the same level of theory. The conversion of silyl-substituted ortho-carboranes into their respective 7, 8-dicarba-nido-undecaborate(1-) derivatives was explored successfully for several examples.

Attempts to prepare a reagent containing the 1-lithioseleno-2-lithio-1,2-dicarba-closo-dodecaborane(12) were only partially successful. The non-cyclic 1-trimethysilylseleno-2-trimethysilyl-1,2-dicarba-closo-dodecaborane(12) could be obtained in mixtures, and a corresponding diselane, formed by hydrolysis/oxidation could be isolated and characterized by X-ray structural analysis. However, the synthesis of related heterocycles failed. Instead, cyclic species derived in principle from 1,2-dilithio- and the 1,2-bis(lithioseleno)-1,2-dicarba-closo-dodecaborane(12) were isolated and characterized. This led to a new 1,5-diselena-2,4-disila-3-oxa-cycloheptane derivative, for which the structure in solution was confirmed by NMR spectroscopy (1H, 13C, 29Si, 77Se NMR) and DFT calculations [B3LYP/6-311+G(d,p)], and the molecular solid-state structure was determined by X-ray diffraction.

Exchange reactions of 2,2-dimethyl-1,3-diselena-2-silacyclopentane and 2,2,3,3-tetramethyl-1,4-diselena-2,3-disilacyclohexane, as the 4,5- and 5,6-[1,2-dicarba-closo-dodecaborano(12)] derivatives, respectively, with boron trihalides (BCl3, BBr3, BI3) and dichlorides (PhBCl2, iPr2NBCl2) afford the corresponding 1,3,2-diselenaborolanes in essentially quantitative yield. The products were characterized in solution by multinuclear magnetic resonance spectroscopy (1H, 11B, 13C, 29Si, 77Se), and for two products, in the solid state by X-ray structural analysis. Attempts to synthesize the boron fluoride failed, and the methoxy derivative was obtained in a mixture with a decomposition product. The gas-phase structures of all relevant products were optimized by DFT hybrid methods [RB3LYP/6-311+G(d.p) level of theory], and NMR parameters (shielding constants and spin–spin coupling constants) were calculated. The calculated data compare well with experimental data, both for the structures and the NMR spectroscopic parameters.

The reaction of the diselenolato-1,2-dicarba-closo-dodecaborane(12) dianion with BF3–OEt2 affords selectively a spirocyclic bis(1,2-dicarba-closo-dodecaborane-1,2-diselena)borate, whereas the analogous reaction with boron trichloride leads mainly to 1,2-bis(ethylseleno)-1,2-dicarba-closo-dodecaborane(12) through ether cleavage. The spirocyclic borate reacts with methanol by cleavage of both Se–B and Se–C bonds. With borane in THF (BH3/THF) and also with LiBH4 exchange reactions take place, which afford the 1,2-dicarba-closo-dodecaborane-1,2-diselenadihydroborate. The molecular structures of both borates as tetrabutylammonium salts were determined by X-ray analysis. In solution, the borates were characterized by multinuclear magnetic resonance spectroscopy (1H, 11B, 13C, 77Se). The gas-phase geometries of the borate anions were optimized [RB3LYP/6-3111+G(d,p) level of theory], and the NMR spectroscopic parameters (chemical shifts and coupling constants) were calculated.

The reaction of the 1,2-diselenolato-1,2-dicarba-closo-dodecaborane(12) dianion [1,2-(1,2-C2B10H10)Se2]2− with dichloromethane (CH2Cl2 or CD2Cl2) in the presence of donor solvents gave 4,5-[1,2-dicarba-closo-dodecaborano(12)]-1,3-diselenacyclopentane, the title compound, which was characterized by X-ray structural analysis and NMR spectroscopy (1H, 11B, 13C, and 77Se). In the presence of pyridine, opening of the icosahedron took place, and a zwitterionic intermediate was isolated and fully characterized in the solid state by X-ray diffraction and in solution by multinuclear magnetic resonance techniques. Although such types of intermediates, prior to deboronation of the ortho-carborane cage, have been proposed several times, this is first example for which the structure has been confirmed unambiguously. This intermediate possesses a nido structure and contains a 7,8-dicarba-nido-undecaborate(1−) anion and a boronium cation, the latter with two pyridine rings linked to the boron atom, which has been extruded from the cage. It was shown that this process is reversible as long as the deboronation is not complete. The formation of the intermediate is accompanied by deboronation, which leads to the 7,8-dicarba-nido-undecaborate(1−) anion. The latter was prepared independently by conventional routes from the title compound, isolated as crystalline material as the tetrabutyl ammonium salt, and characterized by X-ray structural analysis and multinuclear magnetic resonance spectroscopy (1H, 11B, 13C, and 77Se).

The reaction of 1,2-diselenolato-1,2-dicarba-closo-dodecaborane(12) dianion [1,2-(1,2-C2B10H10)Se2]2− with HBBr2–SMe2 affords the dimethyl sulfide adduct of 4,5-[1,2-dicarba-closo-dodecaborano(12)]-1,3-diselena-2-borolane in good yield. The molecular structure was determined by X-ray diffraction, and the solution-state structure was established by NMR spectroscopy (1H, 11B, 13C, 77Se NMR). 11B and 77Se chemical shifts were reproduced by DFT calculations. Attempts were made to abstract dimethyl sulfide, and the parent donor-free compound could be detected in solution. The reactivity of the title compound was studied towards pyridine, Me3SnF, [Pt(PPh3)2(C2H4)], tert-Bu-OH, AlMe3 and AlH3-N(Et)Me2 as well as a hydroborating reagent.

The reaction of various alkynyl(vinyl)silanes containing two alkynyl groups with 9-borabicyclo[3.3.1]nonane (9-BBN) proceeds by regioselective 1,2-hydroboration of the vinyl group in the first step, followed by two intramolecular 1,1-organoboration reactions to afford 1,6-disilapentalene derivatives, fused silacarbacycles with a silole unit. Similarly, the analogous reaction of an alkynyl(allyl)silane gives a 1,7-disilaindene derivative. The products were characterized by multinuclear magnetic resonance (1H, 11B, 13C and 29Si NMR) in solution and in two cases by X-ray structural analysis in the solid state.

The 2-tert-butyl, 2-phenoxy, and 2-diethylamino derivatives of 1,3-bis(trimethylsilyl)-1,3,2-diazaphospha-[3]ferrocenophane were prepared, and the molecular structure of the latter was determined by X-ray diffraction. The phosphines could be oxidized by their slow reactions with sulfur or selenium, and the molecular structures of three sulfides and one selenide were determined. In contrast, the synthesis of oxides was less straightforward. All new compounds were characterized in solution by multinuclear magnetic resonance methods (1D and 2D 1H, 13C, 15N, 29Si, 31P, and 77Se NMR spectroscopy).

Ammonolysis of 1,2-bis[dichloro(methyl)silyl]ethane afforded a crystalline tricyclic silazane along with polymeric material. The crystalline material could be isolated in pure state. It was analyzed by 1H, 13C, 15N and 29Si NMR spectroscopy in solution, by 13C, 15N and 29Si MAS NMR spectroscopy in the solid state, as well as by single-crystal and powder X-ray diffraction. The title compound exists as a single isomer in solution, whereas in the solid state the presence of several modifications is indicated, in particular by the solid-state MAS NMR spectra.