On the product of two Chernikov subgroups

It is shown that if a group G = AB is the product of two subgroups A and B, each of which has an abelian subgroup of index at most 2 satisfying the minimum condition and such that one of the subgroups A or B is of dihedral type, then G is abelian-by-finite with minimum condition.     

Infrared-enhanced multiphoton dissociation of iodobenzene cations

When gas-phase iodobenzene cations in an ion cyclotron resonance spectrometer are irradiated simultaneously with visible 610 nm and IR 977 cm⁻¹ photons, the visible two-photon process is enhanced by a factor of up to three. The experimental pressure and intensity dependences can be modeled using a set of rate equations for the evolution of the populations of different internal energy levels. Modeling suggests that the major mechanism for the mixed visible/IR process is the absorption of several IR photons, followed by the absorption of one visible photon which brings about dissociation: that the visible photoexcitation cross section decreases with increasing ion internal energy: that IR pumping does not compete successfully with relaxation processes near dissociation threshold: and that the IR radiative relaxation time is constant ≈ 500 ms.     

Structure of 1,4,10,19,25,41-C70(CF3)6, isomer with unique arrangement of addends

A novel isomer of C₇₀(CF₃)₆ has been isolated by HPLC from a mixture prepared by trifluoromethylation of C₇₀ with CF₃COOAg. The X-ray structure revealed an unprecedented arrangement of CF₃ groups forming a p³mp ribbon. This result provides additional evidence of the preferable formation of trifluoromethylated fullerene molecules comprising a single continuous ribbon of edge-sharing para- and meta-C₆(CF₃)₂ hexagons.     

Layer Buildup on Two-Layered Porous Substrate by Dip-Coating: Modeling and Effect of Additives on Growth Rate

A model was developed to describe layer buildup on a two-layered substrate during dip-coating. In this model, the growth rate can be used to estimate the permeability of the cast layer. Layers of submicron alumina were dip-coated onto the asymmetric porous substrate to evaluate the model. The layer buildup and properties were studied with different slip additives. Slips were deflocculated with nitric acid or sodium poly(methacrylic acid) (Na-PMAA) to achieve electrostatic or electrosteric stabilization. Properties of the slips with electrostatic stabilization were varied with poly(vinyl alcohol) (PVA) concentration. Properties of the slips with electrosteric stabilization were varied with Na-PMAA concentration. PVA addition decreased the growth rate of the layer by reducing capillary pressure and increasing the viscosity of the filtrate. Electrostatic stabilization of the slip with PVA addition also led to almost complete deflocculation and a rather high density of layers. Na-PMAA addition led to fast growth of the layer. Na-PMAA addition increased the capillary pressure and had a minor effect on the viscosity of the liquid phase. Na-PMAA addition led to an incomplete dispersion of particles and therefore a high porosity of layers. Permeability values of coated layers obtained from the model were compared with permeability values predicted by the Kozeny-Carman equation. In the case of complete deflocculation of the slip, the permeability values estimated with the model correlated reasonably well with the predicted values. Incomplete deflocculation led to higher permeability values than predicted by the Kozeny-Carman equation. Copyright 2000 Academic Press.     

Macroporous thin films for planar chromatography

A procedure for the preparation of macroporous silica films suitable for planar chromatography is described. The films are produced by a low pH catalyses of alkyltrialkoxysilanes in oversaturated solution of pore forming organic compounds. A segregated three phase system yields thick films (10–60 µm) that have good adhesion to silica glass supports, uniform, mirror like surface and intercalated micron-dimension pores that permit capillarity driven elution of solvents through the film. A phase diagram demonstrating optimal operating conditions for macroporous and microporous film formation is introduced and analyzed.     

An ab initio investigation of the collective phenomena accompanying the core ionization in the radical NO

The influence of the reorganization effect of an electron system on potential energy curves of X-ray excited states of the radical nitric oxide has been investigated by the restricted Hartree-Fock method. A dominating role of this collective effect in forming fine vibrational structures in ESCA and X-ray K emission spectra of this radical has been shown by such calculations.     

Selective ortho hydroxylation of nitrobenzene with molecular oxygen catalyzed by the H5PV2Mo10O40 polyoxometalate

Nitrobenzene was regioselectively oxidized to 2-nitrophenol with oxygen in a reaction catalyzed by the H5PV2Mo10O40 polyoxometalate. The reaction was first order in oxygen and catalyst. 15N NMR showed the interaction between nitrobenzene and the polyoxometalate. Use of labeled 18O2, H218O, a competitive kinetic isotope experiment, and use of phenyl-tert-butylnitrone as a spin-trap and identification by EPR provided evidence for formation of a radical intermediate involving a selective intramolecular interaction at the ortho position due to formation of a H5PV2Mo10O40-nitrobenzene complex.     

Binding cooperativity of two different Lewis acid groups at the edge of ferrocene

The binding properties of heteronuclear bidentate Lewis acids, in which an organoboron and an organotin moiety are attached adjacent to each other at one of the Cp rings of ferrocene, have been studied. Treatment of [1,2-fc(SnMe2Cl)(BClMe)] (1-Cl) (fc = ferrocenediyl) with one equivalent of pyridine or 4-dimethylaminopyridine (DMAP) resulted in diastereoselective complexation of boron. Adducts 2 and 3 have been studied by multinuclear NMR, and the stereoselectivity of complexation was further confirmed by single crystal X-ray diffraction of 2. The importance of cooperative effects that involve an intramolecular B-ClSn interaction on the diastereoselectivity is evident from comparison with binding studies on the phenyl-substituted analogue [1,2-fc(SnMe2Cl)(BPhMe)] (1-Ph). Complexation of 1-Ph led to diastereomeric mixtures of adducts 4 and 5, respectively, which were identified by multinuclear NMR including NOESY experiments. The solid-state structure of one of the diastereomers of 5 was confirmed by X-ray crystallography. Facile isomerization was found in solution and the barrier of activation was determined by VT NMR studies (4: Delta(#)(298) = 54.9+/-0.4 kJ mol(-1); 5: Delta(#)(298) = 70.3+/-0.1 kJ mol(-1)). Competitive binding of pyridine to 1-Cl and [FcB(Cl)Me] (Fc = ferrocenyl) showed that cooperative effects between tin and boron lead to significant Lewis acidity enhancement. Binding of a second nucleophile in the presence of excess of base occurred also at boron. The novel zwitterionic complexes [1,2-fc(BMe(py)2)(SnMe2Cl2)] (6) and [1,2-fc(BMe(dmap)(2))(SnMe(2)Cl2)] (7) formed, which consist of boronium cation and stannate anion moieties. The structure of 7 in the solid-state was confirmed by X-ray crystallography. Multinuclear NMR data and competition experiments indicate weak binding of chloride to tin in 7 and partial dissociation in solution.     

Phosphinohydrazines and phosphinohydrazides M(-N(R)-N(R)-PPh2)n of some transition and main group metals: synthesis and characterization: Rearrangement of Ph2P-NR-NR- ligands into aminoiminophosphorane, RNPPh2-NR-, and related chemistry

The reactions of phosphinohydrazines ArNH-N(Ar)-PPh₂ {Ar = Ph (2a), p-Bu^t-C₆H₄- (2b)} with metal silylamides M[N(SiMe₃)₂]_n, {M = Fe(II), Fe(III), Co(II), Ni(I), Cu(I)} or the reactions of lithium salts ArN(Li)-N(Ar)-PPh₂ with metal halides (GeCl₂, ZnCl₂, FeBr₂, CoCl₂, NiBr₂, CrCl₃, MnCl₂) are strongly dependent on nature of a metal and its ligand environment.Early transition metals or non-transition metals form stable phosphinohydrazides M[N(Ar)N(Ar)PPh₂]_n {M = Li, Zn, Ge(II), Mn(II), Cr(III), Fe(II)}.Starting ligand 2a and germylene Ge(NPhNPhPPh₂)₂ (7) were characterized by X-ray analysis.Germanium is coordinated additionally with a phosphorus atom of one of the diphenylphosphine groups.The distance Ge?P was found to be 2.563(1) Å.This coordination leads to an appreciable increase in a pyramidal geometry of nitrogen atoms relatively to a non-coordinated fragment.Late transition metals (Co, Ni, Cu) and metals with enhanced oxidation state (Fe³⁺) cause transformation of a phosphinohydrazide ligand.For Co(II), Ni(II), Fe(III) this leads quantitatively to aminoiminophosphoranates M(NAr-PPh₂NAr)_n.Complex Co[N(C₆H₄Bu^t)-PPh₂N-C₆H₄Bu^t]₂ (11) was characterized by X-ray analysis.Nickel(I) silylamide, (Ph₃P)₂NiN(SiMe₃)₂, being reacted with 2a yields azobenzene complex, (Ph₃P)₂Ni(PhNNPh), while copper(I) silylamide originally forms (PhNH-NPh-PPh₂)₂CuN(SiMe₃)₂ (18).Heating of the latter in toluene solution yields insoluble copper(I) diphenylphosphide, azobenzene, 2a and hexamethyldisilazane.The reaction of hydrazobenzene with Ph₂PCl (1:1) in methylene chloride for three days gives aminoiminophosphorane dihydrochloride[PhNH-PPh₂NPh] · 2HCl (3) in quantitative yield.