Synthesis and Reactivity of Mono‐, Di‐, and,Triiron Selenocarboxylate Complexes

Treatment of the iron selenide (μ‐Se)[CpFe(CO)₂]₂ with one equivalent of 1, 3, 5‐C₆H₃(COCl)₃ gave the organoiron selenocarboxylate complex CpFe(CO)₂SeCO‐3, 5‐C₆H₃(COCl)₂ ( 1 ), which contains two free acid chloride groups. Complex 1 reacted with amines, thiols, and phenols to produce the corresponding amides CpFe(CO)₂SeCO‐3, 5‐C₆H₃(CONR₂)₂ ( 2 ), thioesters CpFe(CO)₂SeCO‐3, 5‐C₆H₃(COSR)₂( 3 ), and aromatic esters CpFe(CO)₂SeCO‐3, 5‐C₆H₃(CO₂Ar)₂ ( 4 ), respectively. Complex 1 was converted into the diacid CpFe(CO)₂SeCO‐3, 5‐C₆H₃(COOH)₂ ( 5 ) or the diamide CpFe(CO)₂SeCO‐3, 5‐C₆H₃(CONH₂)₂ ( 6 ) complexes by reactions with NaOH or NaNH₂, respectively. The bis(seleno)‐1, 3‐(CpFe(CO)₂SeCO)₂‐5‐C₆H₃(COCl) ( 7 ) and tris(seleno)‐carboxylate 1, 3, 5‐(CpFe(CO)₂SeCO)₃C₆H₃ ( 8 ) complexes were also prepared by controlled reaction of 1, 3, 5‐C₆H₃(COCl)₃ with the iron selenide (μ‐Se)[CpFe(CO)₂]₂. Complexes 1 – 8 were characterized by spectroscopic techniques (IR, ¹H‐NMR) and by elemental analysis as well. The X‐ray structures of CpFe(CO)₂SeCO‐3, 5‐C₆H₃(COCl)₂ ( 1 ) and CpFe(CO)₂SeCO‐3, 5‐C₆H₃(COSCH₂Ph)₂ ( 3b ) were determined.     

Functionalization of Pentaphosphorus Cations by Complexation

The chemistry of polyphosphorus cations has rapidly developed in recent years, but their coordination behavior has remained mostly unexplored. Herein, we describe the reactivity of [P₅R₂]⁺ cations with cyclopentadienyl metal complexes. The reaction of [Cp^ArFe(μ‐Br)]₂ (Cp^Ar=C₅(C₆H₄‐4‐Et)₅) with [P₅R₂][GaCl₄] (R=iPr and 2,4,6‐Me₃C₆H₂ (Mes)) afforded bicyclo[1.1.0]pentaphosphanes ( 1‐R , R=iPr and Mes), showing an unsymmetric “butterfly” structure. The same products 1‐R were formed from K[Cp^Ar] and [P₅R₂][GaCl₄]. The cationic complexes [Cp^ArCo(η⁴‐P₅R₂)][GaCl₄] ( 2‐R [GaCl₄], R=iPr and Cy) and [(Cp^ArNi)₂(η^3:3‐P₅R₂)][GaCl₄] ( 3‐R [GaCl₄]) were obtained from [P₅R₂][GaCl₄] and [Cp^ArM(μ‐Br)]₂ (M=Co and Ni) as well as by using low‐valent “Cp^ArM^I” sources. Anion metathesis of 2‐R [GaCl₄] and 3‐R [GaCl₄] was achieved with Na[BArF₂₄]. The P₅ framework of the resulting salts 2‐R [BArF₂₄] can be further functionalized with nucleophiles. Thus reactions with [Et₄N]X (X=CN and Cl) give unprecedented cyano‐ and chloro‐functionalized complexes, while organo‐functionalization was achieved with CyMgCl.     

Numerical Simulation of Turbulent Flow and Heat Transfer in a Three-Dimensional Channel Coupled with Flow Through Porous Structures

This study investigates numerically the turbulent flow and heat transfer characteristics of a T-junction mixing, where a porous media flow is vertically discharged in a 3D fully developed channel flow. The fluid equations for the porous medium are solved in a pore structure level using an Speziale, Sarkar and Gatski turbulence model and validated with open literature data. Overall, two types of porous structures, consisted of square pores, are investigated over a wide range of Reynolds numbers: an in-line and a staggered pore structure arrangement. The flow patterns, including the reattachment length in the channel, the velocity field inside the porous medium as well as the fluctuation velocity at the interface, are found to be strongly affected by the velocity ratio between the transversely interacting flow streams. In addition, the heat transfer examination of the flow domain reveals that the temperature distribution in the porous structure is more uniform for the staggered array. The local heat transfer distributions inside the porous structure are also studied, and the general heat transfer rates are correlated in terms of area-averaged Nusselt number accounting for the effects of Reynolds number, velocity ratio as well as the geometrical arrangement of the porous structures.     

[P3Se4]+: A Binary Phosphorus–Selenium Cation

Although a fairly large number of binary group 15/16 element cations have been reported, no example involving phosphorus in combination with a group 16 element has been synthesized and characterized to date. In this contribution is reported the synthesis and structural characterization of the first example of such a cation, namely a nortricyclane‐type [P₃Se₄]⁺. This cation has been independently discovered by three groups through three different synthetic routes, as described herein. The molecular and electronic structure of the [P₃Se₄]⁺ cage and its crystal properties in the solid state have been characterized comprehensively by using X‐ray diffraction, Raman, and nuclear magnetic resonance spectroscopies, as well as quantum chemical calculations.     

Quasirelativistic f-in-core pseudopotentials and core-polarization potentials for trivalent actinides and lanthanides: molecular test for trifluorides

Calibration studies of actinide and lanthanide trifluorides are reported for actinide and lanthanide scalar-relativistic energy-consistent f-in-core pseudopotentials, respectively, accompanying valence basis sets as well as core-polarization potentials. Results from Hartree–Fock and coupled-cluster singles, doubles, and perturbative triples f-in-core pseudopotential calculations are compared to corresponding data from f-in-valence pseudopotential and all-electron calculations as well as to experimental data. In general, good agreement is observed between the f-in-core and f-in-valence pseudopotential results, whereas due to the lack of experimental data for the actinides only a good agreement of the calculated and experimentally determined bond lengths of the lanthanide systems can be established. Nevertheless, the results indicate that the core-polarization potentials devised here for actinides improve the f-in-core results.     

Spectral parameters for quantitative mobility contrast in NMR imaging of solid polymers

Different procedures based on parameters of the wideline NMR absorption spectrum are presented to obtain localized molecular mobility contrast for imaging of solid polymers. For this purpose a ¹H-NMR imaging technique with magic sandwich echoes is used for acquiring localized wideline spectra. With samples composed of polystyrene and high impact strength polystyrene, and polycarbonate and low density polyethylene a spatial difference in NMR absorption spectrum lineshape and linewidth is displayed. Furthermore, the spatial distribution of rigid and mobile domains in a heterogeneous polymer can be derived from the NMR spectral components. It is demonstrated that a van Vleck moment analysis can be performed from spatially resolved magic echo decays. The second (M₂) and fourth (M₄) moments of the rigid components show considerable variation with the spatial composition of the investigated samples.     

Freezing in forced convection flows inside ducts: A review

The present work gives an overview about the recent developments in research on freezing phenomena in forced convection flows inside ducts. Emphasis is given to the fundamental aspects of the phenomena observed in the solidification processes as well as on the analytical and numerical modelling aspects for this kind of problems. The paper deals with solidification problems inside tubes, parallel plate channels, curved rectangular channels and in diverging rectangular channels. Additionally, some new experimental and numerical results on solidification in duct flows are shown from the current research program in Darmstadt on freezing phenomena.