Magnetochemistry of dimers with iron group ions

General theory of matrix interactions of dimers of iron group ions is considered. Equations for calculation of matrix elements of the exchange energy of dimers and equations for calculation of the magnetic moments of dimers of different d ⁿ configurations and different exchange parameters are reported. The energies of the spin states of dimers are calculated with inclusion of exchange interactions of the first J ₀ and second J ₂ orders, and energy state diagrams for dimers with different spins and exchange energies are reported. For heterospin dimers, equations for calculation of the magnetic moment ?? and magnetic susceptibility ?? are introduced, and for homospin dimers, analytical formulas of calculation are presented. The tables of magnetic moments are calculated and their diagrams as a function of J ₀ for homospin dimers with spins S = 5/2, 2, 3/2, 1, and 1/2 are given. The experimental data are interpreted for Co²⁺ dimers as an example: the experimental and theoretical dependences of ?? and ?? on temperature are considered.     

The combustion synthesis of iron group metal fine powders

The new approach has been developed for the synthesis of nickel (Ni), cobalt (Co) and iron (Fe) powders from the appropriate oxides by the solid combustion method. The reduction was made by sodium azide (NaN₃) at the presence of carbon in the argon atmosphere. The variation of combustion temperature and velocity was performed by using alkali metal salt as an inert diluent. The values of combustion parameters were measured and also the temperature distribution in a combustion wave are obtained. The geometric sizes of reactionary zones and the activation energy of the process were estimated. The optimum conditions for single-phase metal powder synthesis were found. Powders fabricated in this way had cubic structure and particles size about 0.5-2.0 μm for Ni, Co and 1-3 μm for Fe. In a number of cases the formation of spherical particles with the average size about 5-15 μm were observed.     

Direct NO group transfer from S-nitrosothiols to iron centres

A number of S-nitrosothiols react rapidly with the Fe(II) complexes of 2,3-dimercapto-1-propanesulfonic acid (DMPS) and of N-methyl-D-glucamine dithiocarbamate (MGD), transferring the NO group directly to the iron centres.     

The d-electron states of iron group impurity atoms in silicon

The question of the relative arrangement of the crystalline terms is considered, within the framework of crystal field theory, as a function of the location of the impurity atom in the silicon. The results of the corresponding calculations are found to agree with the experimental data.     

Hot atom reactions in neutron irradiated solid iron group metallocenes

Investigation of the hot reactions of the recoil metal nuclides in neutron irradiated solid ferrocene, ruthenocene and osmoscene shows that the retention decreases from ferrocene to osmocene. This observation is ascribed to the effects of recoil energy and the size of the hot zone. The large isotope effect observed between osmium isotopes and between ruthenium isotopes are explained as resulting from the effect of the Auger ionisation produced by internal conversion which takes place in Os-185 and Ru-97 to a greater degree than in their other isotopes. Irradiation of solid metallocenes diluted with an inert solid (silica) showed that the retention in ruthenocene is high and only slightly less than for the pure case whilst the retention of osmocene is very small and the retention of ferrocene is almost zero. The high retention in solid diluted ruthenocene was tentatively attributed to a combination of primary retention resulting from γ cancellation and uptake of recoil momentum by the solid lattice.     

η-Cyclopentadienyl(nitrosyl)iron complexes containing group VA donors

Summary [(-C₅H₅)Fe(NO)(CO)]₂ and (-C₅H₅)Fe(NO)(CO)I are formed when a slow stream of NO is passed through a benzene solution of [(-C₅H₅)Fe(CO)₂]₂ and (-C₅H₅)Fe(CO)₂ I respectively. Similarly NO reacts with (-C₅H₅)Fe(CO)(Ph₃E)I and [(-C₅H₅)Fe(CO)₂(Ph₃E)]I, where E = P, As and Sb, to give (-C₅H₅)Fe(NO)(Ph₃E)I and [(-C₅H₅)Fe(NO)₂(Ph₃E)]I respectively. The complexes were characterized by elemental analyses and i.r. spectra.Reprints of this article are not available.     

NMR spectra of paramagnetic complexes of 1-vinylimidazole with iron group metals

The high-resolution ¹H and ¹³C NMR spectra of 1-vinylimidazole complexes with iron group metals were recorded. The contact coupling in these systems was established in the ¹H and ¹³C NMR spectra. The applicability of the NMR spectra transformed by long-range hyperfine coupling for elucidating the molecular structure of the ligand was shown. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1430–1433, June, 2005.     

Insertion of group ivb metal dihalides into iron—carbon sigma bonds

The insertion reaction of GeCl₂, SnCl₂ and SnBr₂ into the iron—carbon sigma bond in the compounds Cp(CO)₂FeR (R = methyl, ethyl, n-propyl, p-methoxybenzyl, benzyl and p-trifluoromethyl- benzyl), to yield complexes with the Group IV metal bound to iron, is a radical chain process. A small substituent effect is observed in all cases for the benzyl series, the reaction being favoured by increasing electron donating ability of the para substituent. No clear reactivity trend is noted for the other alkyl complexes.     

Phenol-formaldehyde resin route to the synthesis of several iron group transition metal phosphides

Abstract

A series of iron, cobalt and nickel metal phosphides of chemical formula Fe_xP, Co₂P and Ni₂P with high specific surface areas of 331.1, 294.2 and 228.0 m² g^?1, respectively, was firstly synthesized by phenol-formaldehyde resin route. It was found that the as-prepared Co₂P and Ni₂P samples synthesized using phenol-formaldehyde resin as a carbon source showed much higher BET surface areas than those prepared using other carbon sources reported before, including cinnamic strong alkali anion exchange resin, p-phenylenediamine and hexamethylenetetramine. This phenol-formaldehyde resin route was proved to be as universal as traditional H₂ reduction method.     

Inter-level differences in iron group atomic systems in the extended method of calculation

The extended method of calculation has been applied to calculate the inter-level differences of the shell of 3d-electrons in the iron group atomic system. The hydrogen-like radial orbitals have been used. The results are compared with those obtained by ordinary methods of calculation as well as with experimental data.     

The mechanism of group (I) chloride initiated filiform corrosion on iron

The initiation and propagation of filiform corrosion (FFC) on polymer-coated iron following contact with aqueous group (I) chloride salts is investigated using in situ scanning Kelvinprobe (SKP) and ex situ SIMS measurements. Prior to the onset of FFC a circular area of cathodic delamination is observed to grow radially from a penetrative coating defect. The delaminated zone is abundant in group (I) cations, whereas Cl⁻ anions are substantially excluded. As cathodic delamination slows to a halt corrosion filaments initiate at the coating defect and propagate across the delaminated zone at ca. 0.33 μm min⁻¹. Filaments travelling beyond the delaminated zone show only a small (<20%) decrease in propagation rate. It is shown that Cl⁻ is substantially conserved in the filament-head electrolyte, whereas group (I) cations are effectively excluded. When FeCl₂ is used as the initiating salt, a cathodic delamination phase is not observed but FFC occurs as before. The implications of these findings are discussed with respect to the role of cathodic delamination processes in FFC on iron.     

Adsorption of water molecules in the process of electroionization of the iron group metals

The measurements of electroreflection of freshly generated metal surface in aqueous solution of electrolyte allowed to determine duration of the formation of metal-water adsorption complexes. The role of water molecules and OH⁻ ions in dissolution of iron group metals is elucidated.     

Dihydrogen, dihydride and in between: NMR and structural properties of iron group complexes

Tabulating the structures and characteristic NMR properties of 17 iron complexes, 98 ruthenium complexes and 70 osmium complexes that contain dihydrogen or compressed dihydride ligands reveals a variety of trends. The HH bond lengths increase from similar Fe(II) to Ru(II) to Os(II) complexes. Iron(II) displays a narrow range of HH distances for stable complexes. Electronegative atoms Cl and O, when attached on the metal trans to the dihydrogen ligand, result in elongation of the HH bond relative to more electropositive atoms H, C, P and N. The family of cyclopentadienyl ligands also causes this elongating effect. The dihydrogen ligands with short HH distances and weak interactions with the metal, especially on iron and ruthenium are in the fast spinning regime. One exception is the biporphyrin complex of ruthenium with the side-on bridging H₂ ligand which has an HH distance of 118 pm but is in the fast spinning regime. There are some ruthenium complexes with HH distances greater than 110 pm that are in the slow motion regime and several complexes of osmium with HH distances greater than 130 pm that are in this regime. The large J_HH due to quantum mechanical exchange coupling are observable for some of these osmium complexes with HH distances in the range of 140–160 pm. The dihydrogen ligands in many complexes appear to have librational motions or other motions that place them in the intermediate motion regime. New equations to correlate J_HD with HH distances for ruthenium dihydrogen complexes and for osmium dihydrogen complexes are introduced here.     

Studies on the sorption of iron group elements from sea water by the radiotracer method

The methods of radioactive labelling the sea water and the conditions for reaching the equivalence of physico-chemical states of radiotracers and corresponding stable nuclides in sea water are analyzed. The process of bioassimilation, the uptake and release of radionuclides by plankton organisms, is considered as the way of fast stabilization of physicochemical forms of radiotracers in sea water. The data are presented on the sorption of iron, cobalt, nickel and manganese by typical ocean bottom sediments (deep-water red clay, diatomic coze, carbonate deposit).     

Cleavage of P-S bonds and oxygenation by a trinuclear iron carboxylate: synthesis and structures of iron clusters containing group 15/16 anions

The first reactions of the trinuclear oxygen-centred iron carboxylate [Fe(3)(mu(3)-O)(mu(2)-piv)(6)(H(2)O)(3)](piv) (piv=(t)BuCOO(-)) with the neutral ligand precursor [RP(S)(mu-S)](2) (R=4-anisyl) are reported.     

Spectra and structure of iron(III) complexes with carbamide derivatives containing an acetyl group

Equilibria of complex formation reactions of Fe^III in aqueous solutions with CH₃CONHCONH₂ and CH₃CONHCONHCH₃ were investigated by the UV spectral method. The formation of complexes of [Fe(H₂O)_6-nL_n]⁺³ (where n = 1, 2) has been established and their stability constants determined. The following crystalline complexes have been obtained: [Fe(CH₃CONHCONH₂ )₃ ]Cl₃ and [Fe(CH₃CONHCONHCH₃)₃]Cl₃, and their structures investigated using IR and NMR spectra. Results suggest that they are six-membered ring structures. The influence of the polar effects of substituents on the stability of iron(III) complexes with acetylcarbamides has been discussed and mesomeric effects have been shown to dominate inductive effects and work in opposite directions.     

Catalytic activity in water-gas shift reaction of platinum group metals supported on iron oxides

Summary The activity of systems made of a platinum metal supported on Fe₂O₃ in the water-gas shift reaction (WGSR) has been studied. The iron oxide catalysts activity in WGSR are apparently determined by their redox properties that can be improved by addition of platinum metals.