Volume 78, Issue 3-4 - Special issue dedicated to Professor Gerhard Müller from Universität Konstanz on the occasion of his 70th birthday

The sodium salt of theophylline is ferrocenylmethylated at N7 in water using [FcCH 2 NMe 3 ]I. Further alkylation at N9 with various reagents and under different conditions was however unsuccessful. The molecular structures of both ferrocenylmethylated theophylline and sodium theophyllinate were determined by single crystal X-ray diffraction.

The electron density distribution (EDD) of a cyclic tetrasaccharide composed of four benzoylated galactopyranosyl units was calculated from refinement with scattering factors from the invariom library based on X-ray diffraction data downloaded from the Crystal Structural Data Base (CSD). Bond topological and atomic properties have been derived. Benzoyl substituents cause weak intermolecular interactions. These are also visible from low electron density concentrations on the Hirshfeld surface and have an influence on a low X-ray density compared to that of non-substituted carbohydrates, where hydrogen bonds allow a 20% more dense packing. On the electrostatic potential (ESP) surface, a strong polarization between the positive outer belt of 12 benzoyl groups and a negative core region composed of the four galactose sugar molecules exists. The positive benzoyl exterior establishes a repulsive wall between adjacent molecules in the structure.

Orthoamides of alkyne carboxylic acids 17 react with 1,2- and 1,3-dioles to give vinylogous cyclic urea acetals. Analogous reactions with ethandithiol deliver vinylogous thioureas. The condensation of orthoamides 17 with 3,5-dimethyl-4-nitroisoxazol affords 1,1-diamino-butadiene derivatives. From nitro acetaldehyde diethylacetal and orthoamides 17 can be prepared reactive vinylogous urea acetals, which condense with cyano-acetic acid ester under formation of 7,7-diamino-2,4,6-hexatrienecarboxylic acid esters. 5,5-Bis(dimethylamino)-2-nitro-2,4-butadienecarboxylic acid esters, which are accessible from the orthoamides 17 and nitro acetic ester, cyclize to give 5-dimethylamino-pyrrole-2-carboxylic acid esters on treatment with zinc/acetic acid.

Four divinylphenylene-bridged diruthenium complexes [{Ru(CO)(P i Pr 3 ) 2 (L- κ 2 [ N , O ] – )} 2 ( μ -CH=CH-C 6 H 4 -CH=CH-1,4)] ( 2a – 2d) with N , O -chelating 2-hydroxypyridine and 2-hydroxy- or 8-hydroxyquinoline ligands are presented. They were studied by NMR spectroscopy, electrochemical methods and, in their neutral and oxidized states, by IR, UV/Vis/NIR and, if applicable, by EPR spectroscopy. The experimental studies are complimented by (TD-)DFT calculations. Our results indicate that the pyridine-olate complexes 2a,b exist as three isomers with a ratio of about 78:20:2 that differ with respect to the orientation of the N and O donors relative to the CO and alkenyl ligands in the equatorial coordination plane. Only the isomer with both imine N donors trans to the alkenyl ligand is observed for complexes 2c,d with quinolinato ligands. All complexes undergo two consecutive, chemically and electrochemically reversible one-electron oxidations at low potentials. Our results indicate strong contributions of the divinylphenylene bridge to the redox processes and an even delocalization of the electron hole and the unpaired spin density over the entire π-conjugated divinylphenylene diruthenium backbone with only minor involvement of the peripherally attached κ 2 [ N , O ] – donor ligands.

The mixed-valent calcium oxidotellurate(IV,VI) Ca 2 (Te 2 O 7 ) (= Ca 2 (Te IV Te VI O 7 )) and the two calcium oxidotellurate(IV) dichlorides Ca 2 (Te IV O 3 )Cl 2 and Ca 5 (Te IV O 3 ) 4 Cl 2 were obtained from metal chloride salt melts. Structure determination from single crystal X-ray data revealed a unique crystal structure in each case. A common motif in the three crystal structures is the formation of a framework perforated by channels into which the stereochemically active 5 s 2 electron lone pairs E of the Te IV atoms are directed. Ca 2 (Te 2 O 7 ) belongs to category I of the Robin-Day classification of mixed-valent compounds. Its crystal structure features a double chain of condensed trigonal-pyramidal [Te IV O 3 ] and octahedral [Te VI O 6 ] units embedded within a framework of [CaO x ] polyhedra ( x = 7–8). The Cl atoms in the crystal structures of Ca 2 (Te IV O 3 )Cl 2 and Ca 5 (Te IV O 3 ) 4 Cl 2 act as spacers between isolated trigonal-pyramidal [TeO 3 ] units and exhibit weak interactions with the 5 s 2 electron lone pairs E , with Cl⋯ E distances <3.6 Å.

The aerobic oxidation of copper(I) to copper(II) was studied in the ionic liquid (IL) 1- n -butyl-3-methylimidazolium acetate [BMIm][OAc]. Temperatures above 100 °C promote the deprotonation of the C 2 atom of the imidazolium ring and the dissolution of CuCl. 1 H and 13 C NMR spectra indicate the formation of the N-heterocyclic carbene (NHC) complex [NHC] Cu I Cl under inert conditions. Upon aerobic oxidation, air-stable blue-green crystals of [BMIm] 2 [Cu II 2 (OAc) 4 Cl 2 ] precipitate in high yield and the NHC is recovered. X-ray diffraction on a single-crystal of the complex salt revealed a monoclinic structure with space group P 2 1 / n . The centrosymmetric dinuclear acetate complex [Cu 2 (OAc) 4 Cl 2 ] 2– has the paddle-wheel motif and is weakly paramagnetic.

Reaction of zinc(II) chloride, bromide and iodide with 2-methylpyrazine (2-Mepyz) leads to the formation of coordination compounds with the composition ZnX 2 (2-Mepyz) 2 (X = Cl; 1-Cl , Br; 1-Br and I; 1-I ). In the compounds each Zn cation is tetrahedrally coordinated by two halide anions and two 2-methylpyrazine ligands forming discrete complexes. TG-DTA and temperature dependent PXRD measurements prove that upon heating compounds 1  transform into new compounds with the composition ZnX 2 (2-Mepyz) ( 2 ), that are subsequently converted into compounds with the composition (ZnX 2 ) 3 (2-Mepyz) ( 3 ) upon further heating. It was also found that compounds 2 can be prepared directly in solution. For ZnI 2 (2-Mepyz) ( 2-I ) crystals were obtained and characterized by single crystal X-ray diffraction, whereas the crystal structures of 2-Cl and 2-Br were determined ab initio from PXRD data. In these compounds the Zn cations are also tetrahedrally coordinated and linked into chains by bridging 2-methylpyrazine ligands. The (ZnX 2 ) 3 (2-Mepyz) compounds can only be obtained by thermal decomposition, and the products are of poor crystallinity and extremely hygroscopic, which prevented structure determinations.

In a systematic study the Se(IV) and Te(IV) dihalides F 2 E(CH 3 )(C 6 F 5 ), Cl 2 E(CH 3 )(C 6 F 5 ) and Br 2 E(CH 3 )(C 6 F 5 ) (E = Se, Te) have been synthesized and their crystal and molecular structures been investigated by X-ray diffraction and computational methods. The solid-state structures of all compounds show significant correlations between the lengths of the E–C1 bond and the intermolecular E···X (X = F, Cl and Br) contacts, indicating the presence of σ-hole interactions. For comparison, the crystal and gas phase (electron diffraction) structures of Se(CH 3 )(C 6 F 5 ) are presented as well. They show very similar structural parameters in both phases. The structures of the single molecules X 2 E(CH 3 )(C 6 F 5 ) have been analyzed by quantum-chemical methods in terms of their surface potentials. They show significant similarities of their molecular electrostatic-potential topologies ( V s,max ). The magnitude of V s,max correlates with the aggregation pattern.

The reaction of [{Ir(µ-Cl)(coe) 2 } 2 ] ( 1 , coe = cis -cyclooctene) with the bulky tertiary phosphane P( o -tolyl) 3 in dichloromethane at room temperature was investigated. It afforded in good yield the tri-coordinate iridium(I) complex [IrCl{P( o -tolyl) 3 } 2 ] ( 2 ) which was characterized in the solid state by a single-crystal X-ray diffraction study revealing a molecular structure of a rare tri-coordinate complex. The iridium(I) complex is stabilized by an agostic interaction of a hydrogen atom from the methyl group of the bulky phosphane ligand to fill the fourth unsaturated coordination site. The title compound crystallized from dichloromethane/diethyl ether as orange crystals in a mixture of two modifications (monoclinic P 2 1 / c , 2a , and orthorhombic Pbca , 2b ). The co-existence of the two components as a nearly 1:1 mixture in the crystalline bulk material was supported by solid-state 31 P{ 1 H} NMR measurements.

Metathesis reactions designed with the tentative starting stoichiometry ( A 1) + : ( A 2) + : [N(CN) 2 ] −  = 1 : 1 : 2 ( A 1, A 2: Li, Na, K, Rb and Cs) were used to get a complete picture of the compounds and structures that are formed in this regime of dicyanamides with two different alkali-metal cations. Next to solid solutions and phase separations of the respective pseudo-binary dicyanamides, the new compound Rb 1.667 Cs 0.333 [N(CN) 2 ] 2 was found and structurally characterized as a disorder variety of the KCs[N(CN) 2 ] 2 structure. Rb 1.667 Cs 0.333 [N(CN) 2 ] 2 adopts the monoclinic space group C 2/ c and the unit-cell parameters a  = 1387.73(8), b  = 1005.00(6), c  = 1451.29(8) pm, β  = 117.175(3)° for Z  = 8. Its crystal structure is very closely related with those of β -Rb[dca] and KCs[dca] 2 ([dca] −  ≡ [N(CN) 2 ] − ) and so are the vibrational spectra. These three quasi-isostructural compounds are compared in detail. A synopsis of the crystal structures (either already reported or discussed here for the first time) for all combinations in the ( A 1) + : ( A 2) + : [N(CN) 2 ] − systems is presented and the behavior of those not forming a distinct compound is discussed.

Investigations in the ternary system Eu–Al–Pt led to the discovery of Eu 4 Al 13 Pt 9 , a new representative exhibiting a coloring variant of the Ho 4 Ir 13 Ge 9 type structure. The orthorhombic structure was refined based on single crystal X-ray diffraction data ( Pmmn , Wyckoff sequence e 9 b 3 a 5 , a = 415.38(1), b = 1149.73(2), c = 1994.73(5) pm, wR 2 = 0.0622, 1901 F 2 values, 88 variables) and full atomic ordering was observed for all atoms. The structure features a complex [Al 13 Pt 9 ] δ – network with the Eu atoms occupying hexagonal prismatic cavities. The bonding situation of this new platinide was investigated via quantum-chemical calculations. According to Density Functional Theory (DFT) the title compound has to be described as a polar intermetallic material with a covalently bonded [Al 13 Pt 9 ] δ – polyanion showing strong Pt–Al alongside weak Al–Al and Pt–Pt bonding and Eu cations in the cavities.

Mixing an aqueous solution of K 8 [Nb 6 O 19 ]⋅16H 2 O with a DMSO/H 2 O solution of Cu(ClO 4 ) 2 · 6 H 2 O and cyclen at room temperature afforded crystallization of blue crystals of [(Cu(cyclen)) 6 Nb 6 O 19 ]⋅[ClO 4 ] 4 ·≈4H 2 O after slow evaporation of the solvents. The crystal structure contains the Lindqvist anion [Nb 6 O 19 ] 8– which is covalently expanded by six symmetry-related [Cu(cyclen)] 2+ complexes via Nb- μ 2 -O-Cu bridges yielding the positively charged [(Cu(cyclen)) 6 Nb 6 O 19 ] 4+ cluster shell. The ClO 4 − anions and crystal water molecules reside in the empty spaces of the packed clusters. The compound shows two electronic d-d transitions at energetic positions explaining the blue color.

The synthesis of beryllium halide etherates and the solution behavior in benzene, dichloromethane, and chloroform was studied by NMR, IR, and Raman spectroscopy. Mononuclear units of [Be X 2 ( L ) 2 ] ( X  = Cl, Br, I; L  = Et 2 O, thf) were identified as the favorably formed species in solution. Treatment of the mononuclear diethyl ether beryllium halide adduct with one equivalent beryllium halide formed the dinuclear compounds [Be X 2 (OEt 2 )] 2 ( X  = Cl, Br, I). The solid-state structures of [BeCl 2 (thf) 2 ] and [BeBr 2 (thf) 2 ] have been determined by single crystal X-ray diffraction analysis. [BeI 2 (thf) 2 ] decomposed in all solvents. In CD 2 Cl 2 the salt [Be(thf) 4 ]I 2 was formed, whereas in C 6 D 6 and CDCl 3 , BeI 2 precipitated and [BeI(thf) 3 ] + , [Be(thf) 4 ] 2+ together with the thf ring-opening product [Be( μ 2 -O(CH 2 ) 4 I)I(thf)] 2 were observed in solution.

The silicides RE 3 Pd 20 Si 6 ( RE = Sc, Y and Lu) were synthesized from the elements by arc-melting. The structures of Y 3 Pd 20 Si 6 and Lu 3 Pd 20 Si 6 were refined from single crystal X-ray diffractometer data: Mg 3 Ni 20 B 6 type, F m 3 ‾ m $Fm\overline{3}m$ , a = 1216.04(8) pm, wR = 0.0328, 219 F 2 values, 14 variables for Y 3 Pd 20 Si 6 and a = 1211.69(10) pm, wR = 0.0374, 217 F 2 values, 14 variables for Lu 3 Pd 20 Si 6 . The isotypy of Sc 3 Pd 20 Si 6 was confirmed on the basis of a Guinier powder pattern ( a = 1202.8(3) pm). The RE 3 Pd 20 Si 6 structures contain two crystallographically independent RE sites with relatively large coordination numbers, i.e. RE 1@Pd 16 and RE 2@Pd 12 Si 6 . These polyhedra are arranged in a CaF 2 related pattern with RE 2@Pd 12 Si 6 forming the fcc substructure and the RE 1@Pd 16 polyhedra filling the tetrahedral voids. The silicon atoms have slightly distorted square antiprismatic palladium coordination (4 × 239 pm Si–Pd1 and 4 × 245 pm Si–Pd2). Temperature dependent magnetic susceptibility measurements of the Lu 3 Pd 20 Si 6 sample indicate Pauli paramagnetism.

As part of our program on the synthesis and reactivity of the pyrrole-imidazole alkaloids from marine sponges, the synthesis of the 2-azido analog of the key marine natural product oroidin is reported. In addition, desaminooroidin and its alkyne analog were synthesized. Red-Al reduction of a 4-alkynylimidazole intermediate afforded the ( E )-alkene, without having to pass via the ( Z )-alkene. Coupling of 4,5-dibromopyrrole-2-carboxylic acid with 2-azidoimidazolylprop-2-en-1-amine was best achieved by EDCI-mediated coupling, which was superior to using the corresponding trichloromethylketone. Use of t- BuOK in acetonitrile can be recommended for the coupling of non-azidated alkenyl and alkynylimidazoles. The azido analog of oroidin underwent click cycloadditions to imidazolyltriazoles.

The metastable compound CeGe 3 was obtained by high-pressure high-temperature synthesis from pre-reacted Ce and Ge at 3 GPa of pressure and 1873 K, with subsequent annealing over several hours at 1173 K. The product crystallises in a 2 × 2 × 2 superstructure of the cubic Cu 3 Au-type structure with space group F m 3 ‾ m $Fm\overline{3}m$ and a  = 8.6970(2) Å. CeGe 3 decomposes at 520(10) K into CeGe 2− x and elemental Ge.

The praseodymium metaborate molybdate(VI) PrBO 2 MoO 4 was synthesized by solid-state reaction methods at 850 °C under an argon atmosphere and identified by its powder X-ray diffraction pattern. The polycrystalline sample was placed in a Walker-type multianvil press, where pressure-induced crystal growth at 1 GPa and 850 °C was successful, yielding single crystals suitable for structure determination. PrBO 2 MoO 4 crystallizes monoclinically in the space group P 2 1 / c (no. 14) with the unit cell parameters a  = 10.1735(2), b  = 4.1479(1), c  = 11.9090(3) Å, β  = 116.52(1)°, and four formula units per cell.

By the reaction of (dimethylphosphoryl)methanamine ( dpma ) with one equivalent of zinc(II) chloride in a concentrated hydrochloric acid solution and subsequent slow evaporation of the solvent, the title compound ( dpma H)ZnCl 3 was obtained in quantitative yield. The primary reaction product mainly consists of larger brick-shaped colorless and smaller cuboide colorless crystals. Long-time storage over several months of these crystals in the mother liquor yielded a third polymorph ( P 2 1 / n ; a  = 9.6639(1); b  = 10.0271(1); c  = 11.2446(1) Å; β  = 98.964(1)°) of this compound. Similar to the two other modifications, its crystal structure consists of a zwitterionic dpma HZnCl 3 complex containing the cationic dpma H + ligand, which coordinates the zinc atom through its oxygen atom. Hydrogen bonds connect neighboring zwitterionic complexes to a layered structure. The motif of a hydrogen bonded dimer, similar to that found in the chain structure of polymorph I , is also present, but in the title structure these dimers form hydrogen bonds in two dimensions.

A metastable polymorph of Ti 3 Sn (called c-Ti 3 Sn) exhibiting the cubic Cr 3 Si-type structure was prepared by a mechanochemical route. At temperatures of about 450 °C, it transforms to the well-known hexagonal phase (Ni 3 Sn type, called h-Ti 3 Sn). 0.5% of iron was incorporated into the material originating from the steel beaker and the steel balls. However, quantum-chemical calculations show that this should not lead to a stabilization of the Cr 3 Si type. c-Ti 3 Sn shows a single signal at an isomer shift of δ  = 1.70(1) mm s −1 in its 119 Sn Mössbauer spectrum at 78 K.

C-S-H–PCE nanocomposites are known to perform as highly effective seeding materials in Portland cement. Here the effectiveness of a C-S-H–PCE nanocomposite admixture on early strength development of eco-friendly cements (clinker blended with up to 35% fly ash or calcined clay) was investigated. First, C-S-H–PCE nano-composites were synthesized from Ca(NO 3 ) 2 /Na 2 SiO 3 via a co-precipitation method and their particle size distribution was analyzed. Differently structured PCE comb polymers based on IPEG chemistry were used in the synthesis. Nanofoils of ∼50 nm length were identified as most promising seeding material. Furthermore, addition of such C-S-H–PCE nanofoils was found to substantially increase mortar strength at early ages, particularly after 6–24 h of curing. Isothermal heat flow calorimetry and in-situ XRD measurements indicate that silicate hydration in cement is significantly accelerated. Most remarkably, C-S-H–PCE also was confirmed to speed up the pozzolanic reaction of fly ash and calcined clay and to stimulate the formation of hemicarbo aluminate (Hc), especially in calcined clay cement. Thus, C-S-H–PCE can foster the more widespread use of eco-friendly CEM II/III cements.

4-(2,6-Di(2 H -indazol-2-yl)pyridin-4-yl)benzoic acid ( 1 ) and 10-(2,6-di(1 H -pyrazol-1-yl)pyridin-4-yl)anthracene-9-carboxylic acid ( 2 ) were required for adsorption studies on Ag(111), with a view to subsequent iron(II) complexation and formation of well-ordered spin-responsive self-assembled monolayers. While the generation of these compounds has remained elusive, several intermediates and by-products were obtained, potentially useful as dipyrazolylpyridine-related derivatives and for metal ion coordination. 3,5-Dichloro-2,6-diindazolylpyridine-4-amine, which forms as a mixture of regioisomers, was synthesised, the mixture separated, and the components characterised (3,5-dichloro-2,6-di(2 H -indazol-2-yl)pyridin-4-amine; 3,5-dichloro-2-(1 H -indazol-1-yl)-6-(2 H -indazol-2-yl)pyridin-4-amine; 3,5-dichloro-2,6-di(1 H -indazol-1-yl)pyridin-4-amine). Their iron(II) complexes have been prepared and fully characterised, including single crystal X-ray structure determination. The complexes are instructive examples of the influence of ligand design (“steric jamming”) on the spin-crossover (SCO) activity of Fe II centres. Bulky substitution, which entails twisted ligand conformation, increases intramolecular crowding. This prevents contraction of the metal coordination sphere, which would be a prerequisite for thermally inducible SCO. Mössbauer spectroscopy has revealed that the complexes remain predominantly high-spin (HS) between 20 and 200 K, and that a mixture of conformational HS isomers is present in the microcrystalline solid.