Diphosphacarbollide analogues of the C5H5- anion: isolation of the nido-di- and triphosphacarboranes 7,8,9-P2CB8H10, [7,8,9-P2CB8H9]-, [7,8,10-P2CB8H9]-, and 7,8,9,10-P3CB7H8

Treatment of a solution of excess PCl(3) and PS (PS = "proton sponge" = 1,8-dimethylamino naphthalene) with arachno-4-CB(8)H(14) (1) in CH(2)Cl(2), followed by hydrolysis of the reaction mixture, resulted in the isolation of the eleven-vertex diphosphacarbaborane nido-7,8,9-P(2)CB(8)H(10) (2) (yield 34%) as the main product. Other products isolated from this reaction were the phosphacarboranes nido-7,8,9,10-P(3)CB(7)H(8) (3) (yield 5%) and closo-2,1-PCB(8)H(9) (4) (yield 15%). Compound 2 can be deprotonated by PS in CH(2)Cl(2) or NaH in diethyl ether to give the [nido-7,8,9-P(2)CB(8)H(9)](-) (2(-)()) anion, which gives back the original compound, 2, upon re-protonation. Thermal rearrangement of anion 2(-) (Na(+) salt) at 350 degrees C for 2 h produced the isomeric [nido-7,8,10-P(2)CB(8)H(9)](-) (5(-)()) anion, which was isolated as a PPh(4)(+) salt (yield 86%). Multinuclear ((1)H, (11)B, (31)P, and (13)C), two-dimensional [(11)B-(11)B] COSY, (1)H{(11)B(selective)}, (1)H{(31)P(selective)}, and gradient-enhanced ([(1)H-(13)C] HSQC) magnetic resonance measurements led to complete assignments of all resonances which are in excellent agreement with the structures proposed. Coupling constants, (1)J((31)P,(13)C), (2)J((31)P,C,(1)H), and (1)J((31)P,(31)P), were calculated using the DFT method B3LYP/6-311+G(d,p). The molecular geometries of all compounds were optimized ab initio at a correlated level of theory (RMP2(fc)) using the 6-31G basis set, and their correctness was assessed by comparison of the experimental (11)B and (13)C chemical shifts with those calculated by the GIAO-SCF/II//RMP2(fc)/6-31G method. The computations also include the structures and chemical shieldings of the still unknown isomers [nido-7,10,8-P(2)CB(8)H(9)](-) (6(-)) and [nido-7,9,8-P(2)CB(8)H(9)](-) (7(-)).     

1,5-bis(dicarboxymethylaminomethyl)-2,6- dihydroxynaphthalene as a selective spectrofluorimetric reagent for calcium

1,5-Bis(dicarboxymethylaminomethyl)-2,6-dihydroxynaphthalene (BDDN) forms fluorescent complexes with aluminium, barium, beryllium, calcium, magnesium and strontium. All the complexes have 2:1 metal :ligand ratios. Barium, calcium, magnesium and strontium exhibit maximal fluorescence at pH 11.7, with excitation and emission maxima at 385 and 445 nm respectively. Aluminium and beryllium show maximal fluorescence at pH 5.8 and 5.2 respectively, the excitation and emission maxima being at 370 and 405 nm. The formation of the calcium complex provides a highly sensitive and selective determination of calcium in the range 10/2-500 ng. The fluorescence measurement of calcium should be made within 5 min of mixing the solutions because of the instability of the reagent at the given pH. Potassium cyanide may be used as a masking agent and ter- or quadrivalent cations should be removed by preliminary extraction with 8-hydroxyquinoline in chloroform at pH 6.0. In such conditions, of 33 cations studied, only magnesium (>20 ng), strontium (>70 ng) and barium (>150 ng) caused interference in the determination of 300 ng of calcium. Among 16 anions examined, only EDTA interfered seriously.     

Field alpha-spectroscopy of radon (<Superscript>222</Superscript>Rn) and actinon (<Superscript>219</Superscript>Rn) progeny in soil gas: Locating a radon source

Summary The activities of²¹⁸Po,²¹⁴Po and²¹¹Bi were determined in samples obtained of soil/gas. Sampling work was taken in Jáchymov (Czech Republic) at the outcrop of the Geister-vein,by electrostatic precipitation from filtered soil gas on stainless steel disks.The samples were measured in a field laboratory using a semi-conductor alpha-spectrometer.The activities of²¹⁸Po,²¹⁴Po and²¹¹Bi were calculated.Samples taken from active dump material (near-by radon source) exhibited a high²¹¹Bi/²¹⁴Po ratio, while those of the vein outcrop (a relatively deeper source) had a low ratio.A mathematical model was employed to determine the radon age calculated from the actinon/radon input ratio.This varied in a range of 5.6 to -7.7 seconds.Negative age values are probably caused by the preference for actinon, which rapidly comes into equilibrium with the source of this gas.     

Transfer reaction of the polystyrene radical with electron-acceptor molecules of tetrachlorophthalanhydride

The transfer constants (C_s) of the polystyrene radical with some derivatives of phthalic acid have been determined. Among the agents used, tetrachlorophthalanhydride (TCPA) differs distinctly from other compounds by its value of C_s 3·1 × 10^?3 for thermal and 3·4 × 10^?3 for initiated polymerization of styrene. The values of C_s for phthalanhydride, dimethyl phthalate, and tetrachlorodimethyl phthalate are lower by two decimal orders. The considerable decrease in the degree of polymerization of styrene prepared in the presence of TCPA is mainly attributed to the increased reactivity of chlorine atoms in TCPA induced by the acceptor effect of anhydride ring. Participation of a TCPA-styrene complex in transfer reaction has been assumed but not proved.     

Polychlorinated polyamides—III. Synthesis and characterization of polyamides derived from perchloroterephthaloyl dichloride

Six new polyamides have been prepared either by polymerization in solution or by interfacial polymerization by reacting perchloroterephthaloyl dichloride with aromatic diamines. The polymers were characterized by i.r. spectroscopy, elemental analysis, DSC, and TGA. The glass transition temperature, the melting temperature, and the thermal decomposition temperature have been determined. In order to estimate the molecular weights, intrinsic viscosities were determined. Some of the polymers showed high thermal stability.     

Stability of tin etiopurpurin

Formulations of the tin etiopurpurin (SnET2) have been observed to undergo a spectral change on storage in dimethylformamide solution. This results in an alteration in the action spectrum, with enhanced photodynamic activity at lower wavelengths and decreased activity at 660 nm. On the basis of structural considerations, a reduced analog of SnET2 was prepared with an absorbance maximum at 640 nm. Formation of this product, termed SnET2H(2) relieves steric strain inherent in the parent molecule. Nuclear magnetic resonance, spectral and photodynamic data are consistent with the formation of SnET2H(2) during SnET2 storage. Slight modifications in the original synthesis are also reported, resulting in improved yields of intermediate products.     

Synthesis,characterization and a thermogravimetric study of copper,cobalt and tin mono- and bis-adducts with ethyleneurea,ethylenethiourea and propyleneurea

This paper describes the synthesis, characterization and a thermogravimetric (t.g.) study of 11 adducts of general formula MCl₂·nL (M = Cu, Co and Sn; n = 1 and 2 for Sn, and 2 for Cu and Co; L = ethyleneurea eu, ethylenethiourea etu, and propyleneurea pu). The i.r. results shows that the eu and pu adducts are coordinated through oxygen, whereas for etu nitrogen is the coordination site. The (C=O) or (C=S) trend is: Cu > Co > Sn. The t.g. curves show that the adducts release ligand molecules in a single mass loss step. As regards considering adducts with the same stoichiometry, the observed thermal stability trend is: etu > pu > eu.     

Quantitative separation of zinc traces from cadmium matrices by solid-phase extraction with polyurethane foam

A system for separation of zinc traces from large amounts of cadmium is proposed in this paper. It is based on the solid-phase extraction of the zinc in the form of thiocyanate complexes by the polyurethane foam. The following parameters were studied: effect of pH and of the thiocyanate concentration on the zinc extraction, shaking time required for quantitative extraction, amount of PU foam necessary for complete extraction, conditions for the separation of zinc from cadmium, influence of other cations and anions on the zinc sorption by PU foam, and required conditions for back extraction of zinc from the PU foam. The results show that zinc traces can be separated from large amounts of cadmium at pH 3.0±0.50, with the range of thiocyanate concentration from 0.15 to 0.20 mol l⁻¹, and the shaking time of 5 min. The back extraction of zinc can be done by shaking it with water for 10 min. Calcium, barium, strontium, magnesium, aluminum, nickel and iron(II) are efficiently separated. Iron(III), copper(II) and cobalt(II) are extracted simultaneously with zinc, but the iron reduction with ascorbic acid and the use of citrate to mask copper(II) and cobalt(II) increase the selectivity of the zinc extraction. The anions nitrate, chloride, sulfate, acetate, thiosulphate, tartarate, oxalate, fluoride, citrate, and carbonate do not affect the zinc extraction. Phosphate and EDTA must be absent. The method proposed was applied to determine zinc in cadmium salts using 4-(2-pyridylazo)-resorcinol (PAR) as a spectrophotometric reagent. The result achieved did not show significant difference in the accuracy and precision (95% confidence level) with those obtained by ICP–AES analysis.     

The chemistry and the stereochemistry of poly(N-alkyliminoalanes) : V. The preparation and crystal structure of the pentamer [(HalN-i-Pr)2(H2AlNH-i-Pr)3]

The compound [(HAlN-i-Pr)₂(H₂AlNH-i-Pr)₃] has been prepared and the crystal and molecular structure determined by an X-ray analysis, carried out with three-dimensional data collected on a diffractometer. The molecule is made up of a cyclohexane-type ring, [(HAlN-i-Pr)₂(H₂AlNH-i-Pr)], in skewboat conformation, on each side of which is bonded an -H₂AlNH-i-Pr- bridging unit between a nitrogen atom and an aluminum atom of the ring. The molecule lies on a binary axis of the crystal, but this symmetry is fulfilled only by a statistical orientation of the asymmetric molecular units (the statistical model is not however completely defined). The AlN bond lengths range from 1.901 to 1.985 Å; the average NC bond length is 1.527(9) Å. Main crystal data are: monoclinic space group C2/c; a = 10.15(2), b = 21.64(3), c = 12.84(2) Å, β = 111.9(5)°; Z = 4; calculated density 1.095 g/cm³. The structure was solved by direct methods and block-matrix least-squares converged to an R value of 5.6%.