Trägerfixierte Organometallkomplexe. IV. Strukturuntersuchungen an neutralen und kationischen (Ether-phosphan)palladium(II)-Komplexen

Supported Organometallic Complexes. IV. Structural Investigations on Neutral and Cationic (Ether-phosphane)palladium(II) Complexes . Reaction of the (ether-phosphane) ligands PhP(R)CH₂—D ( 2a?c ) [D=CH₂OCH₃: R=Ph ( a ), (CH₂)₃Si(OCH₃)₃ ( b ), (CH₂)₃SiO_3/2 ( b ′); D= R=(CH₂)₃Si(OCH₃)₃ ( c ), (CH₂)₃SiO_3/2 ( c ′)] with Cl₂Pd(COD) ( 1 ) results in the formation of Cl₂Pd(P — O)₂ ( 3a?c ). Cleavage of Cl^? from 3 with AgSbF₆ yields the cationic, monochelated complexes [ClPd(P — O)(P ∩ O)]⁺ ( 4 a—c ) (P — O: η¹-P-coordinated; P ∩ O: η²-O ∩ P-coordinated). 4 a crystallizes in the monoclinic space group P2₁/c with the lattice constants a=1 062,4(2), b=1 912,2(4) und c=1 635,5(3) pm, β=101,22(3)° and Z=4 (R=0,0341; R_w=0,033). With water 3 b, c and 4 b, c are subjected to polycondensation to give the supported complexes 3 b′, c′, 4 b′, c ′. The structure 3 b′, c′, 4 b′, c ′ is investigated by comparison of their ³¹P CP MAS data with the ³¹P{¹H} NMR spectra of their soluble precursors 3 b, c, 4 b, c . ¹³C CP MAS NMR spectra of 3 b′, c ′ and 4 b′, c ′ indicate η¹-P- and η²-O ∩ P-coordination of the ligands. The polysiloxane network of 4 b ′ was inspected by contact time variation of the ²⁹Si CP MAS NMR spectra and it appeared that 77% of the Si—O units are crosslinked, corresponding to a ratio T₄:T₃:T₁=67:100:10.     

Darstellung und eigenschaften von und reaktionen mit metallhaltigen heterocyclen: XXV. Synthese und eigenschaften neuer platina- und rhodacycloalkane durch substitution und oxidative addition einer CCl-bindung

The platinacyclopentane derivative [Cl(CH₂)₃R₂P](Cl)$\text{PtPR}{}_2\text{CH}{}_2\text{CH}{}_2\text{CH}{}_2$ is formed by action of Cl(CH₂)₃PR₂ on Pt(COD)₂ in n-hexane via the not isolable Pt[PR₂(CH₂)₃Cl]₂ (R  C₆H₁₁) by oxidative addition of a CCl bond to platinum. [μ-CIRh(CO)₂]₂ reacts in benzene with Cl(CH₂)₃PR₂ under partially CO substitution to give the stable intermediate Cl(OC)Rh[PR₂(CH₂)₃Cl]₂. In boiling toluene oxidative addition of a CCl bond to rhodium occurs under formation of the phospharhodacyclopentane [CI(CH₂)₃R₂P] Cl₂(OC)-$\text{RhPR}{}_2\text{CH}{}_2\text{CH}{}_2\text{CH}{}_2$ (R  C₆H₅). The ³¹P{¹H}-NMR spectra of the rhodium compound is characterized by an ABX system, that of the platinum by superposition of an ABX pattern with an AB spectrum.     

The sum-of-squares hierarchy on the sphere and applications in quantum information theory

Mathematical Programming - We consider the problem of maximizing a homogeneous polynomial on the unit sphere and its hierarchy of sum-of-squares relaxations. Exploiting the polynomial kernel...     

Semidefinite Approximations of the Matrix Logarithm

Foundations of Computational Mathematics - The matrix logarithm, when applied to Hermitian positive definite matrices, is concave with respect to the positive semidefinite order. This operator...     

Simulating the Dickman distribution

In this paper, we give a simple algorithm for sampling from the Dickman distribution. It is based on coupling from the past with a suitable dominating Markov chain.     

Spectrophotometric Determination of Some Fluoroquinolone Antibacterials by Ion‐pair Complex Formation with Cobalt (II) Tetrathiocyanate

A new simple extractive spectrophotometric method has been developed for the determination of levofloxacin (I), norfloxacin (II), and ciprofloxacin (III) in pure form and tablets. The method is based on the formation of blue‐colored ion‐pair associates between the drugs and the inorganic complex, cobalt (II) thiocyanate, at pH 2.5. Those ion‐pair associates are readily extracted into an n‐butanol‐dichloromethane solvent mixture (3.5:6.5) and determined spectrophotometrically at 623 nm. The concentration range is 20–240 μg mL^?1 for the three studied drugs. The proposed method was successfully applied to determine these drugs in their tablet formulations, and the results are in good agreement with those obtained by the reference methods.     

Associated stop-Higgs production at a linear collider and extraction of stop parameters

We calculate stop-stop-Higgs production at a linear collider. Combining the measurements from the pair production of the lightest stop and that of the mass of the Higgs, we show how, in a scenario where only the lightest stop and the lightest Higgs are accessible, one could extract the mass of the heavier stop and infer some useful information on the supersymmetric parameters. Received: 19 November 1998 / Published online: 18 June 1999