Zur Darstellung phosphido‐chalkogenido‐verbrückter Dirheniumkomplexe vom Typ Re2(μ‐PCy2)(μ‐ER)(CO)8 (E = S,Se, Te; R = org. Rest)

Synthesis of Phosphido Chalcogenido Bridged Dirhenium Complexes of the Type Re₂(μ‐PCy₂)(μ‐ER)(CO)₈ (E = S, Se, Te; R = org. Residue) The reaction of Re₂(μ‐Br)(μ‐PCy₂)(CO)₈ with nucleophiles MER (M = Na, Li; E = S, Se, Te; R = org. residue) gives via substitution of the bromido bridge phosphido chalcogenido bridged dirhenium complexes of the general formula Re₂(μ‐PCy₂)(μ‐ER)(CO)₈. The new compounds were characterized by IR, ¹H and ¹³C NMR spectroscopic data and by elemental analyses. In addition the molecular structures for E = S, Se, Te and R = Ph as well as for E = S and R = H, n‐Bu, 2‐pyridyl have been established by single crystal X‐ray analysis. ¹³C NMR spectra of Re₂(μ‐PCy₂)(μ‐EPh)(CO)₈ (E = S, Se, Te) prove that the sulfur and selenium compounds are at room temperature dynamic molecules due to inversion of the pyramidal chalcogenido bridge. The tellurium compound, however, is rigid on the time scale of ¹³C NMR spectroscopy. Eventually the reactivity of the SH function of the novel complex Re₂(μ‐PCy₂)(μ‐SH)(CO)₈ was investigated by reaction with Re₂(CO)₈(MeCN)₂. In toluene at 90 °C the novel spirocyclic complex Re₂(μ‐PCy₂)(CO)₈(μ₄‐S)Re₂(μ‐H)(CO)₈ was formed by SH oxidative addition.     

Calcium Thiolates and Selenolates: Synthesis and Structures

The synthesis and structural characterization of a family of calcium thiolates and selenolates is described. In the solid state the compounds adopt either contact pairs, as observed in Ca(THF)₄(SMes*)₂ ( 1 ), (Mes* 2,4,6‐tBu₃C₆H₂), and Ca(THF)₄(SeMes*)₂, ( 2 ), or separated ions as shown in [Ca(18‐crown‐6)(HMPA)₂][SeMes*]₂ ( 3 ). The two different ion association modes are induced by addition of specific donors. The compounds were prepared by metalation involving the reaction of elemental calcium dissolved in dry liquid ammonia with either HSMes* or Mes*SeSeMes*. All compounds were characterized by X‐ray crystallography, NMR and IR spectroscopy.     

Ferrocenyl‐Functionalised Molybdenum Imido Complexes: An Approach to Redox‐Tunable Olefin Polymerisation Catalysts

[(FcdippN)₂MoCl₂(DME)] ( 1 ) was used as starting material for the synthesis of the novel ferrocenyl‐functionalised complexes [(FcdippN)₂Mo(CH₂CMe₂Ph)₂] ( 2 ), [(FcdippN)₂Mo(OTf)₂(DME)] ( 3 ), and [(FcdippN)Mo(CHCMe₂Ph)(O^tBu)₂] ( 4 ) (Fcdipp = 4‐ferrocenyl‐2,6‐diisopropylphenyl). The crystal structure of 2 was determined. Electrochemical investigations by cyclic voltammetry suggest a communication of the ferrocenyl unit and the molybdenum centre in these compounds. The monoalkylation of [(DippN)₂MoCl₂(DME)] ( 5 ) to [(DippN)₂Mo(CH₂CMe₂Ph)Cl] ( 6 ) (Dipp = 2,6‐diisopropylphenyl) was achieved.     

Stimulation and binding properties of polyelectrolyte multilayers verified by ATR‐FTIR spectroscopy

We report on the deposition and properties of multilayers composed of reactive polymers on planar surfaces. As reactive polymers the poly cations poly(ethylene‐imine), poly(L‐lysine) (PLL), poly(allylamime) (PAA) and the polyanions poly(acrylate) (PAC), poly(vinylsulfate), poly(maleate‐co‐olefines) were used. ATR‐FTIR Spectroscopy was adopted to study deposition, binding and stimulation properties of polymer multilayers. The binding of charged species of different molecular size such as rhodanide anions and sodium oleate from solution was examined, whereby binding was found to be dependent on the charge of the outermost layer. For these two analytes a selectivity parameter Q, defined as the ratio between the adsorbed amount obtained at the negatively charged and that at the positively charged surface, respectively, was determined. Furthermore, swelling experiments on multilayer assemblies of PLL and PAC exposed to mixtures of ethanol/water (10–70% EtOH content) were carried out. Our experiments gave evidence, that the PLL layers showed a more significant increase in density than the PAC layers. The conformation of PLL incorporated into multilayers could be changed by pH variation.     

Pseudopolymorphs in Industrial Use

The common property of organic and inorganic solids of forming pseudopolymorphs are of very high importance in chemical and pharmaceutical industry. Depending on the solvent some compounds form hydrates (with water) or solvates (with other solvents) in different stoichiometric proportions. Pseudopolymorphs exhibit different physical properties like density, habitus, stability, dissolution rate or bioavailability as known for polymorphs. Phase transformations, existing between the different phases, including the anhydrous or nonsolvate form, vary e.g. with temperature, pressure, relative humidity and solvent. If these process parameters are changed, phase transformations cannot be excluded, either prefered or surprising. In a common project industrial relevant properties of pseudopolymorphs are elucidated on a scientific basis.     

Kristallstruktur von Caesiumtetrafluorooxotellurat(IV) Cs2TeOF4

Crystal Structure of Cesiumtetrafluorooxotellurate(IV) Cs₂TeOF₄ Solid state reaction of cesium fluoride, cesium pentafluorotellurate(IV), and tellurium dioxide in the molar ratio 3 : 1 : 1 yields colourless single crystals of cesium tetrafluorooxotellurate(IV). The compound crystallizes in a structure analogous to potassium pentafluoroantimonate(III) (Cmcm, Z = 4, a = 669.5(1), b = 1464.0(2), c = 717.09(7) pm). The characteristic feature is the presence of discrete pseudooctahedral tetrafluorooxotellurate(IV) anions. The structure of this complex anion could be determined for the first time. It contains a short Te–O_ax bond of 177.5 pm (bond order about 1.7) and long Te–F_eq bonds of 207.2 pm (bond order about 0.6). The position of the tellurium atom deviates only slightly from the equatorial plane (O_ax–Te–F_eq: 89.0°).