Volume 36, Issue 5

The first three-membered P 2 AS heterocycle, tri-tert-butyl-diphosphaarsa-cyclopropane (tri-tert-butyl-diphosphaarsirane) (1) was synthesized by [2+1] cyclocondensation of K(t-Bu)P-P(t-Bu)K with t-BuAsCl 2 in n-pentane at - 78 °C. Tetra-tert-butyl-1,2-di-phospha-3,4-diarsa-cyclobutane (2), tetra-tert-butyl-triphosphaarsa-cyclobutane (3) as well as (t-BuP) 4 and five-membered cycloarsaphosphanes are also formed. The diphospha-arsa-cyclopropane 1 could be isolated in a pure state. It forms two diastereomers, of which the isomer with trans-orionted tert-butyl groups at the phosphorus atoms is the most stable. The 31 P NMR parameters of the four-membered cycloarsaphosphanes 2 and 8 are reported

Tetragonal aluminium sulfide crystallizing with the spinel defect structure of the β-In 2 S 3 type has been prepared at ambient pressure. IR and Raman spectra of this compound and of α-Al 2 S 3 are reported and discussed in relation to their crystal structures

77 Se chemical shifts of compounds CF 3 SeX exhibit an extraordinary good linear correlation with Huggins‘ electronegativities of χx. A range of 1051 ppm is covered for χx values between 1.9 and 3.15. Effective electronegativities are derived from the δ( 77 Se) values. For some compounds unexpected 77 Se chemical shifts are found. This indicates an uncommon electronic constitution at selenium. Electron excitation energies are reported for some of the compounds and their importance for the paramagnetic shielding term is discussed. The relative shieldings of the tellurium compounds are analogous to those of the corresponding selenium compounds. In contrast to 77 Se, the 19 F shieldings of CF 3 EX compounds (E = chalcogen) depend inversely on the electronegativity of E and X. The 13 C chemical shifts do not correlate with the χx values. NMR data of some CF 3 Se(IV) and CF 3 Te(IV) compounds are also reported for comparison

The crystal structure of the compound Na 2 [N(CH 3 ) 4 ] 4 HPW 11 O 39 · 7H 2 O was solved by X-ray diffraction. It crystallizes in the space group C2/m with lattice parameters a= 23.895 Å, b = 11.417 Å, c = 28.930 Å, β= 126.0°. The distances between the tungsten atoms and the kind of bridging by oxygen atoms prove the α-isomer. The differences between the vibration spectra of α-undecatungsto-phosphate and α-dodecatungstophosphate are discussed

The missing compounds of the series of sulfurdiimines R 1 - N = S = N-R 2 with R 1/2 = C 6 H 5 , C 6 F 5 , C 6 H 5 S, C 6 F 5 S were prepared, and all ten compounds investigated. Thermal stability, UV/VIS-, IR-and 19 F-NMR-spectra depend strongly on the combination of the substituents

Trimethylstibine dichloride and dibromide, resp., react with antimony(III) chloride and bromide, resp., to yield the 1:1 addition compounds (CH 3 ) 3 SbCl 2 · SbCl 3 (1) and (CH 3 ) 3 SbBr 2 · SbBr 3 (2). The crystal and molecular structure of 1 and 2 are determined by X-ray analysis, the Raman spectra discussed and assigned

Cyclotetraphosphazanes (2) with three P III and one P v , and (3) with two P III and P v atoms are prepared from 1 with methyl iodide. NMR spectra of 2 are compared with those of the recently prepared [1] 4. The crystal structure of 3 shows the molecule to have a crystallographic inversion centre. Thus cis-trans isomerisation must have taken place during the working up procedure. Alkylation has severe consequences on bond distances and bond angles of the cyclotetraphosphazane ring system, in contrast to M(CO) 5 complexation at the same positions as shown in a similar case recently [8]

The calcium isotope separation in the liquid-liquid extraction system H 2 O/CHCl 3 is investigated using [2.2.1] and [2.2.2] cryptands for complex formation as well as without complexing agent. An extraction procedure is used which allows the transfer of larger amounts of calcium into the CHCl 3 phase although the high distribution coefficient favours calcium in the H 2 O phase. Without complexing agent in the extraction system, enrichment of the lighter calcium isotopes is already evident in the CHCl 3 phase which is just the same as when using [2.2.1] cryptand. In the case of [2.2.2] cryptand as a complexing agent, the isotope separation is higher. The separation factor is calculated to be α = 1 + ε = 1.011 for 40 Ca/ 48 Ca without complexing agent or with [2.2.1] cryptand and α = 1.015 in the system with [2.2.2] cryptand. For 40 Ca/ 44 Ca the ε-value is smaller by nearly a factor of two. These separation factors are the highest which are determined in chemical systems for calcium isotopes

H 2 reacts with [Ir{(Ph 2 P) 2 N-p-C 6 H 4 CH 3 } 2 ]Cl · 3 C 6 H 6 (1) to give cis-[Ir(H) 2 {(Ph 2 P) 2 N-p-C 6 H 4 CH 3 } 2 ]Cl · CH 2 Cl 2 (2a). By reaction of 2a with NaBPh 4 cis-[Ir(H) 2 {(Ph 2 P) 2 N-p-C 6 H 4 CH 3 } 2 ]BPh 4 (2 b) is obtained. Refluxing of 2a in CH 2 Cl 2 yields trans-[lr(H) 2 {(Ph 2 P) 2 N-p-C 6 H 4 CH 3 } 2 ]Cl · 1/2 CH 2 Cl 2 (3a), which undegoes metatheses with NaBPh 4 to trans-[Ir(H) 2 {(Ph 2 P) 2 N-p-C 6 H 4 CH 3 } 2 ]BPh 4 (3b). 3a is also formed by refluxing of 1 in methanol in the presence of oxygen. Oxidative addition of HCl to 1 and reaction with NaBPh 4 yields trans-[Ir(H)(Cl){(Ph 2 P) 2 N-p-C 6 H 4 CH 3 } 2 ]BPh 4 (4b). The new compounds are characterised by their IR, Raman, 31 P{ 1 H} PFT and 1 H NMR Spectra

An optically active 1-phosphino-2-aminopropane, prepared from ephedrine, has been used for the Rh(I) catalyzed asymmetric hydrogenation of α-acetamido cinnamic acid. Optical yields up to 77 percent were obtained. Low stereoselectivity has been found using 1,4-bis(diphenylphosphino)-2,5-dibenzylpiperazine and a polystyrene bound bisdiphenyl-phosphine, obtained from phenylalanine. The preparation of optically active piperazines from α-amino acids is reported

The 13 C NMR chemical shifts of N,N-dimethylbenzamide in thirty solvents have been measured at high dilution. The solvent induced chemical shifts (s.i.c.s.) of the carbonyl group carbon atom in twenty three solvents and the thermodynamic barriers to rotation about the C-N bond in eleven solvents are linearly related to the solvent parameter, E T (30). Multi-parametric analysis of the carbonyl s.i.c.s. indicates hydrogen bond donor effects are more important than polar effects. Rotational barriers for N,N-dimethylbenzamide may be determined by measurement of the 13 C chemical shift of the carbonyl group in a particular solvent. The s.i.c.s. of the aromatic ring carbon atoms may be explained by the polarization of the aromatic π electron system induced by the solvent enhanced polarization of the dimethylcarboxamido moiety. Hydrogen bonding solvents and polar solvents result in two effective dipoles on the dimethylcarboxamido moiety, which polarize the aromatic π electron system differently

The one and two-electron oxidations of water soluble ionic zinc porphyrins (Zinctetra-methylpyridylporphyrin, ZnTMPyP, Zinc-tetra-p-sulfonato-phenyl-porphyrin, ZnTPPS, and Zinc-tetra-p-carboxy-phenylporphyrin, ZnTPPC) leading to the porphyrin Π-cations and Π-dications have been investigated in water by electrochemical (cyclic voltammetry and controlled potential electrolysis) and chemical methods. The half-wave potentials for the oxidation are shown to be markedly dependent on the charge on the β-substituents. While the one-electron oxidations for all these porphyrins are reversible, the dication formation leads to labile isoporphyrins as intermediates

⊿G for the reaction R ·+ + R ·- → 2 R + ⊿G was calculated according to ⊿G = -(IP-EA) = -⊿ E 1 for the reaction in gas phase under ideal conditions. The result was compared with ⊿H in solution measured calorimetrically and the entropy term measured voltammetrically according to ⊿G = ⊿H - T⊿S. Both values for ⊿G agreed satisfactorily. From this it was derived that the solvation energies of R ·+ and R ·- compensate mutually. The Coulomb energies have little influence on ⊿G only

Monocyclic 1,3thiazolium-4-olates (10) react with o-quinonoid compounds to give [π4 + π4] cycloadducts (12, 13); tricyclic 1,3-thiazolium-4-olates (14, 15) yield compounds (17, 18, 19, 20) which can formally be derived from a ketene tautomer (C). 1,3-Dithiolylium-4-olates are borderline cases; both [π4+ π2] (32) and [π4 + π4] adducts (34) were obtained

1,3-Oxazolium-5-olates (1) 1,3-thiazolium-5-olates (11) react with o-benzoquinones (3) and α-naphthoquinone to give adducts (4, 5, 6, 15) which can formally be derived from ketone valence tautomers of 1 and 11. 9,10-Phenanthrenequinone and 1 a yield a compound (10) which possibly results from an initially formed [π4 + π4] adduct (7) with subsequent loss of CO 2 . Consistent with this view is a product (14) of the reaction between 9,10-phenanthrenequinone and 11. The structure of 14 has been determined by X-ray crystallography

N,N′-Diarylsulfonyl- and N,N′-Dibenzoyl-o-benzoquinone-diimines (4) react remarkably easy with 1,3-diarylbenzo[c]furans (5) to give [π4 + π4] cycloadducts (6). In one case (6a) the chair and boat conformer of this type of adduct could be isolated and the conformations clarified by X-ray crystallography. On heating compounds 6 can rearrange intramolecularly to give 2H-benzimidazoles (7)

It is shown that the apatite phases of composition Ca 10-x Na x (PO 4 ) 6-x (SO 4 ) x F 2 crystallize in a monoclinic unit cell, which is related to those of pure fluoroapatite by doubling the b-parameter. Some comparisons with related systems are made and a possible explanation for the origin of the small monoclinic distortion is advanced

Na 3 FeSe 3 can be synthesized by the reaction of sodium carbonate with iron sponge at 1000 K under a stream of hydrogen saturated with selenium or by heating a mixture of sodium hydride and iron sponge with selenium in a glass ampoule with a temperature gradient (700/800 K). X-ray investigation on single crystals revealed the structure of Na 3 FeSe 3 , isotypic with that of Na 3 FeS 3 . The iron and selenium atoms form isolated [Fe 2 Se 6 ]-anions, consisting of two edge-sharing tetrahedra, with which the sodium atoms build a three-dimensional array

From an aqueous solution of cupric acetate containing an excess of KSCN and hexamethy- lenetetramine crystals of the title compound could be obtained. An X-ray structure analysis showed that the cuprate(II) anion has trigonal bipyramidal geometry. The three equatorial positions are occupied by NCS groups, the axial positions by the hexamethylenetetramine molecules

Frozen samples of aqueous solutions of oxidized Pt 6-methyl-uracil “blue” were studied by ESR spectroscopy at temperatures T ranging between - 196 °C and - 10 °C. When T was raised a distinct change in the line pattern was observed at about -35 °C. The resulting type of spectrum is very similar to the ESR spectrum of MAGNUS’ Green Salt. The observed effect is suggested to be due to a change of the nature of the system’s electronic states possibly indicating a structural rearrangement

Quantum yields of hydrogen peroxide photolysis increase with the square root of concentration of added Cu(II). The cupric ions are photo-catalytically active already at trace concentrations (10 -7 ), i.e., at the concentrations present in any real reaction system. Hydrogen peroxide photolysis is completely suppressed on addition of complexing agents such as EDTA. It is believed that no hydrogen peroxide photolysis would occur in complete absence of photo-catalytically active transition metal ions

Of the title aldehydes 1 and 2, the isomers 1 are more strongly hydrated when kept in dioxan + water or hexadeuterioacetone + deuterium oxide mixtures, respectively. The uncatalysed reaction R-CHO + H 2 O →R-CH(OH) 2 proceeds much faster with compounds 1

On irradiation of trans-di-tert-butylethylene at 185 nm in pentane the sterically congested cis-isomer was formed in ca. 40%. This π-π* excitation constitutes a convenient, direct method for the preparation of such usually difficult to prepare olefins