NMR Knight shift studies in SmSn3 — Extension to low temperatures

The ¹¹⁹Sn Knight shift in SmSn3 has been measured in the temperature range 15—300 K, and it is found that the 4f-contribution to the Knight shift does not show a sign reversal in this temperature interval. The range of crystal field parameters for which simultaneous fit to the magnetic susceptibility and the extended Knight shift results in SmSn3 is obtained can be substantially narrowed from that reported earlier.     

3-Nitroso-4-Hydroxy-5,6-Benzocoumarin as a Specific Reagent for the Detection of Iron in Microamounts

Complexation of 3-nitroso-4-hydroxy-5, 6-benzocoumarin with iron (II) is used to detect iron in presence of various ions present in the scheme of semi-micro qualitative analysis. The method finds application in detection of iron in alloys, inorganic salts and various pharmaceutical products.     

The polarography of oximes: II. 1,2-Acenaphthaquinone monoxime

Polarography of 1,2-acenaphthaquinone monoxime has been carried out in buffers (pH 3.5–13.0) of constant ionic strength 0.5 M and 40% alcohol $\text{v}\text{v}$ at 25 ± 0.5 °C. The oxime group underwent diffusion-controlled reduction (4e) over the whole pH range. The number of electrons involved in the reduction was found by coulometric method as well as by incorporating the values of diffusion coefficients, obtained by using a McBain-Dawson cell, into the Ilkovi? equation. Koutecky's method has been used to compute the kinetic parameters (αn_aand ?log K_f.h) for the reduction of the oxime group and a reduction mechanism is proposed.     

Metal chelates in vinyl polymerization. II. Mechanism of initiation by Fe(DPM)3

The nature of the interaction between the unsaturated monomer and the chelate, Fe(DPM)₃, is studied in detail. The interaction is found to occur only in solution. The stoichiometry of interaction and the equilibrium constant are evaluated. With the help of spectral evidence, attempts are made to point out the specific sites of interaction.     

Some structural and thermodynamic studies of clathrate hydrates

X-ray and neutron diffraction studies show argon and krypton to preferentially form clathrate hydrates of structure II, rather than structure I as previously assumed; methane and hydrogen sulphide do form structure I. Re-examination of solid-solution thermodynamic theory shows that structure II is basically the more stable; structure I is generally formed only when the guest molecule is in the size range that favours occupancy of the 14-hedral over the 12-hedral cages. For molecules too large to enter the 12-hedra the relative stability of structure II is greatest at 0°C, in agreement with the observed sequence of change of stability of cyclopropane hydrate: I to II at –16° and II to I at 1.5°. Carbon dioxide hydrate is observed to decompose on prolonged standing at 105K in accord with the low-temperature instability predicted by Miller.     

Complexes of some rare earth metals with 1-amino-4-hydroxyanthraquinone

La, Ce(III), Pr, Nd and Sm(III) form very stable reddishviolet 1:1 complexes with 1-amino-4-hydroxyanthraquinone in methanol. The stability constants are very similar.     

Preparation and characterization of some stereochemically rigid seven-coordinate η-cyclopentadienyltris(N,N-dialkyldithiocarbamato)hafnium(IV) complexes

Summary N,N-Dialkyldithiocarbametohafnium(IV) complexes of the type -CpHf(S₂CNR₂)₃, (R = Me or Et) have been prepared in nonaqueous media by reacting dichlorodicyclopentadienylhafnium(IV) with sodium salts of substituted dithiocarbamic acids. Conductance and i.r. studies show that these complexes are nonelectrolytes in which all of the dithiocarbamate ligands are bidentate. A coordination number of seven may be assigned to hafnium(IV) in these complexes, 'H n.m.r. spectra of the complexes in CDCI₃ at ambient temperature (30°) indicate that the metal centered rearrangement and the S₂C N bond rotation are both slow on the n.m.r. time scale. A capped octahedron configuration is suggested for these complexes.Author to whore all correspondence should be addressed.