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.     

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°).     

Synthesis of oxazoline functionalized polypropene using metallocene catalysts

Using two different zirconocene/MAO catalyst systems, propene was copolymerized with the comonomers 2‐(9‐decene‐1‐yl)‐1,3‐oxazoline and 2‐(4‐(10‐undecene‐1‐oxo)phenyl)‐1,3‐oxazoline, respectively. The catalysts used were rac‐Et[Ind]₂ZrCl₂ and rac‐Me₂Si[2‐Me‐4, 5‐BenzInd]₂ZrCl₂. Up to 0.53 mol‐% oxazoline could be incorporated into polypropene. Oxazoline content, molecular weight, degree of isotacticity and melting behavior were dependent on the catalyst system, comonomer structure and comonomer concentration in the feed.     

An Experiment on Averaging in Extinction Measurements

The discrete nature of particles leads to fluctuations, in both space and time, of the radiation transmitted through a disperse system. The result of a transmission or extinction measurement is commonly expressed, however, as an average value and consecutively converted to a concentration measurement. The experiment discussed here shows that different concentration measures (volume concentration and surface concentration) can be obtained from the same measurement, depending on which level of the signal treatment the averaging procedure is introduced.