Probing the influence of steric bulk on anion binding by triarylboranes: comparative studies of FcB(o-Tol)2, FcB(o-Xyl)2 and FcBMes2

Steric crowding brought about on pyramidalization at boron has been predicted computationally to be of central importance to the strength and selectivity of anion binding by triarylboranes. The role of steric factors in systems containing a ferrocenyl reporter unit has been systematically probed in the current study by comparison of the F(-)/CN(-) binding properties of FcB(o-Tol)(2) (1, o-Tol = C(6)H(4)Me-2), FcB(o-Xyl)(2) (2, o-Xyl = C(6)H(3)Me(2)-2,6) and FcBMes(2) (3, Mes = C(6)H(2)Me(3)-2,4,6)), both in solution and in the solid state. Somewhat surprisingly, the inclusion of an extra ortho-methyl aryl substituent (e.g. for 2/3vs.1) is found to have a relatively small effect on the binding affinities of these boranes (e.g. log(10)K(CN) = 5.94(0.02), 4.73(0.01), 5.56(0.02), for 1, 2 and 3 respectively). Consistent with this observation, the degree of pyramidalization at boron determined for the cyanide adducts [1·CN](-), [2·CN](-) and [3·CN](-) in the solid state is also found to be essentially invariant (∠C(aryl)-B-C(aryl) = 338, 337, 337°, respectively), as are the B-CN and mean B-C(aryl) distances. In the solid state at least, it is apparent that the adverse steric effects potentially brought about by increasing ortho substitution are mitigated by a greater degree of synchronous rotation of the aryl substituents about the B-C(aryl) bonds. Thus a mean inter-plane angle of 71° is observed for [1·CN](-) while the corresponding values for [2·CN](-) and [3·CN](-) are 78° and 79°.     

A simulation of neutron interaction from Am–Be source with the CR-39 detector

Presented in this paper is a simulation of the interaction of neutrons emitted from a cylindrical Am–Be source with a CR-39 detector. A Fortran90 program, called Neutron.f90, has been written to determine the specifications of secondary particles (alpha particle or proton) and the kinematics of the interactions. A Monte Carlo method was used to simulate which interactions occurred with the constituents of the CR-39 detector, H, C and O atoms. Due to the detector composition, elastic and nonelastic scattering of neutrons is possible. In this paper, nonelastic scattering includes: inelastic scattering; the emission of an alpha particle (n,α) reaction and the emission of a proton (n,p) reaction. Cross sections of other reactions are very small and negligible in comparison with the above mentioned. The energy deposited per unit mass per one neutron was calculated. In addition the contribution to the energy deposited by the alpha particles and protons were determined separately. The program Neutron.f90 computes the coordinates of points in which interactions occur i.e. where secondary particles appear. The energy and angular distributions of protons are also represented in this paper. Another Fortran90 program, called Track_Visibility.f90, was written to calculate the number of visible proton tracks and to calculate the energy deposited per one neutron per one visible track.     

The Hermite Scheme for Semilinear Singular Perturbation Problems

A numerical method for singularly perturbed semilinear boundary value problems is given. The method uses the fourth order Hermite scheme on a special discretization mesh. Its stability and convergence are investigated in the discrete $L^1$ norm.     

Synthesis and characterization of two Ni(II) complexes with furfural s-methylthiosemicarbazone

Synthesis of two Ni(II) complexes with furfural S-methylthiosemicarbazone (HL) of the formula [Ni(HL)₂(H₂O)₂](ClO₄)₂ (A) and [Ni(HL)₂(ClO₄)₂] (B) are reported. Compound A was obtained from an ethanolic solution of Ni(ClO₄)₂·6H₂O and HL, whilst compound B was produced by heating compound A to 378 K. An X-ray analysis of the complex A showed that it has a trans(H₂O)-trans(HL) octahedral configuration in which HL behaves as a bidentate (NN) ligand. On the basis of the IR and electronic spectra as well as the magnetism, it was found that the compound B has also an octahedral configuration in which, HL and ClO₄ groups, are coordinated.     

Coordination and Activation of the BF Molecule

No CO : Fluoroborylene (BF), isoelectronic with CO and N₂, can be trapped by a transition metal. The structurally characterized complex [{CpRu(CO)₂}₂(μ‐BF)] contains an unsupported bridging BF ligand, which is unprecedented in the structural chemistry of CO. With AlCl₃ , metal‐bound CO coordinates through the O atom without bond rupture, while the more polar and less π‐bonded BF ligand is heterolytically cleaved (see picture).

     

Synthesis,Characterization and X-Ray Crystal Structure of the Tri Aqua (3-Hydroxy-5-Hydroxymethyl-2-Methylpyridine-4-Carboxaldehyde-3-Methylisotiosemicarbazone: k<Superscript>3</Superscript>, O<Superscript>3</Superscript>, N<Superscript>7</Superscript>, N<Superscript>10</Superscript>) Ni(II) Nitrate

Abstract  

The title complex triaqua (3-hydroxy-5-hydroxymethyl-2-methylpyridine-4-carboxaldehyde-3-methylisothiosemicarbazone-k³,O³,N⁷,N¹⁰)Ni(II) nitrate ([Ni(PLITSC)(H₂O)₃](NO₃)₂, 1) represents the second transition metal complex incorporating an isothiosemicarbazide-pyridoxal based Schiff base that has been crystallographically characterized. Complex 1 crystallizes in a P21/n space group, with lattice constants: a = 11.2254(1) ?, b = 12.9941(2) ?, c = 12.8663(2), β = 96,7713(5)°, V = 1863.64(4) ?³, Z = 4, F(000) = 1016, R ₁ = 0.0681, wR ₂ = 0.1201. The central Ni(II) cation is found in a six-coordinate octahedral geometry formed by the tridentate Schiff base ligand PLITSC and three water molecules. The identity of 1 was further confirmed by elemental analysis, IR spectra, and conductometric and magnetochemical measurements.     

Isolation of a Bis(oxazol‐2‐ylidene)–Phenylborylene Adduct and its Reactivity as a Boron‐Centered Nucleophile

An isolable phenylborylene species supported by two oxazol‐2‐ylidene ligands was synthesized and structurally characterized. Computational studies revealed the presence of lone‐pair electrons on the boron atom in this molecule; therefore, there are eight electrons around the three‐coordinate boron center. The nucleophilic property was confirmed by the reactions with trifluoromethanesulfonic acid and [(thf)Cr(CO)₅], which gave the corresponding conjugate acid and a chromium–borylene complex, respectively.     

A preliminary survey of natural radionuclides in soil and indoor radon in the town of Niš, Serbia

Journal of Radioanalytical and Nuclear Chemistry - The activity concentration of natural radionuclides in the samples of soil from the town of Ni? were measured using the gamma spectroscopy...