Die Kristallpackung von (PPh4)2[NiCl4] · 2 MeCN und PPh4[CoCl0,6Br2,4(NCMe)]

The Crystal Packings of (PPh₄)₂[NiCl₄] · 2 MeCN and PPh₄[CoCl_0.6Br_2.4(NCMe)] (PPh₄)₂[NiCl₄] · 2 MeCN was obtained from the reaction of PPh₄Cl and NiCl₂ in acetonitrile in the presence of S₂Cl₂, PPh₄[Cl₂H] being a side product. The product of the reaction of CoS₂ with S₂Br₂ (containing rests of S₂Cl₂) at 400 °C was treated with PPh₄Br in acetonitrile yielding PPh₄Br₃ and PPh₄[CoCl_0.6Br_2.4(NCMe)]. The crystal structures of the title compounds were determined by X‐ray diffraction. (PPh₄)₂[NiCl₄] · 2 MeCN (space group I 4, a = 1839.3 pm, c = 1375.3 pm) has a crystal packing derived from the BiPh₄[ClO₄] structure type with a fourfold increased unit cell and one half of the ClO₄^– positions substituted by pairsof acetonitrile molecules. The crystal structure of PPh₄[CoCl_0.6Br_2.4(NCMe)] (space group I4₁/a, a = 1804.7 pm, c = 3198.8 pm) is related to the AsPh₄[RuNCl₄] type with an eightfold increased unit cell. The [CoCl_0.6Br_2.4(NCMe)]^– ions are disordered in two orientations and some halogen positions are randomly occupied by Cl and Br atoms. Family trees of group–subgroup relations show the symmetry relations.     

Average‐case analyses of first fit and random fit bin packing

We prove that the First Fit bin packing algorithm is stable under the input distribution U{k−2, k} for all k≥3, settling an open question from the recent survey by Coffman, Garey, and Johnson [“Approximation algorithms for bin backing: A survey,” Approximation algorithms for NP‐hard problems, D. Hochbaum (Editor), PWS, Boston, 1996]. Our proof generalizes the multidimensional Markov chain analysis used by Kenyon, Sinclair, and Rabani to prove that Best Fit is also stable under these distributions [Proc Seventh Annual ACM‐SIAM Symposium on Discrete Algorithms, 1995, pp. 351–358]. Our proof is motivated by an analysis of Random Fit, a new simple packing algorithm related to First Fit, that is interesting in its own right. We show that Random Fit is stable under the input distributions U{k−2, k}, as well as present worst case bounds and some results on distributions U{k−1, k} and U{k, k} for Random Fit. © 2000 John Wiley & Sons, Inc. Random Struct. Alg., 16: 240–259, 2000     

Kaliumheptachlorodioxodimolybdat(V), KMo2O2Cl7

Potassium Heptachlorodioxodimolybdate(V), KMo₂O₂Cl₇ KMo₂O₂Cl₇ was obtained at 400 °C from the reaction of SCl₂ with molybdenum which contained traces of potassium. Its crystal structure is monoclinic, space group C2/c, a = 1094.1, b = 1139.1, c = 1018.0 pm, β = 110.16°, Z = 4. In the Mo₂O₂Cl₇^– ion two coordination octahedra share a common face with three chlorine atoms. The crystal structure can be derived from the CsNiCl₃ type by vacating one third of the Ni and two thirds of the Cs positions. The crystallographic group-subgroup relationship is given.     

Extreme Differences in the Interactions of `Bare' Fe+ and Fe2+ with Hydrogen Peroxide: Fenton Chemistry in the Gas Phase

The interaction of bare iron mono‐ and dications with hydrogen peroxide in the gas phase is studied by ab initio calculations employing the B3LYP/6‐311+G* level of theory. For the monocation, the quartet and sextet coordination complexes Fe(H₂O₂) are high‐energy isomers that easily interconvert to the more stable iron dihydroxide monocation Fe(OH) and hydrated iron oxide (H₂O)FeO⁺ (quartet) or dissociate into FeOH⁺+OH^. (sextet). On the dication surface, however, the order of stabilities is reversed in that Fe(H₂O₂)²⁺ (quintet) corresponds to the most stable doubly charged species, while the formal Fe^IV compounds Fe(OH) and (H₂O)FeO²⁺ are higher in energy.     

Eine neuartige Methode zur Analyse kombinatorischer Substanzbibliotheken mittels paramagnetischer Reporter

A Novel Method to Identify Chemical Compounds of Combinatorial Libraries by the Use of Paramagnetic Tags An EPR method to identify non‐destructively chemical compounds bound to a single solid‐phase‐synthesis bead for combinatorial chemistry applications is discribed. During synthesis chemical inert paramagnetic substances can be attached in small amounts to a solid‐phase‐synthesis resin for tagging of organic compounds or even reaction steps. The identification of single members of a combinatorial library in short time and high sensitivity can be carried out by using an EPR‐spectrometer.     

Kaliumtetrachlorooxomolybdat(V), KMoOCl4

Potassium Tetrachlorooxomolybdate(V), KMoOCl₄ KMoOCl₄ was obtained at 200 °C in small yield as a side‐product from the reaction of S₂Cl₂ with molybdenum which contained 0.7% of potassium (the main product was MoS₂Cl₃). Attempts to increase the yield by adding stoichiometric amounts of KOH or of KCl + H₂O failed. An attempt to produce KMoOCl₄ by the reduction of MoOCl₄ with KI yielded K₃Mo₂Cl₉ and a small amount of K₂MoOCl₅. The crystal structure of KMoOCl₄ is monoclinic, space group P2₁/c, a = 657,1; b = 901,6; c = 2327,3 pm; β = 92,81°, Z = 8. Square‐pyramidal MoOCl₄^– ions are associated to infinite zigzag chains by Mo…Cl contacts.