Volume 58, Issue 8

TeI 3 [AsF 6 ] is formed from Te, I 2 , and AsF 5 in liquid SO 2 . At room temperature light red crystals of the hemi SO 2 solvate TeI 3 [AsF 6 ] · 0.5 SO 2 are obtained from a saturated solution. The crystal structure (orthorhombic, Pnnm, a=1107.41(2), b=1866.58(3), c=1207.00(2) pm at 123 K, Z =8) consists of pyramidal TeI 3 + cations (Te-I = 267 pm), almost regular octahedral [AsF 6 ] − anions and of SO 2 molecules which show disorder for the O atom positions. A remarkable feature of the crystal structure is the arrangement of the TeI 3 + ions that are pairwise associated, facing each other with the I atoms and forming large voids between each other. This causes the significantly lower density of TeI 3 [AsF 6 ] · 0.5 SO 2 (3.88 Mgm −3 ) in comparison to the unsolvated form (4.20 Mgm −3 , Pass more 1981).

The failure of the sum of van der Waals radii axiom to provide information about donor-acceptor interactions in 8-dimethylamino-naphth-1-yl phosphines and their derivatives called for alternative methods. The coupling constants J(C,H) of the Me 2 N groups proved useful and indicate that in these compounds, N→P interactions are negligible.

The phase diagrams of the systems Bi 2 S 3 -BiX 3 were constructed from results of DTA and total pressure measurements and x-ray analysis. The phases: BiSCl, Bi 4 S 5 Cl 2 and Bi 19 S 27 Cl 3 for X = Cl; BiSBr and Bi 19 S 27 Br 3 for X = Br; BiSI and Bi 19 S 27 I 3 for X = I exist on the boundary lines. The enthalpies of formation and standard entropies of the phases follow from the coexistence decomposition pressure functions. The data are: ΔH°B(BiSCl f,298 ) =−49,6 ± 1,6 kcal/mol S°(BiSCl f,298 ) = 30,3 ± 2,5 cal/K·mol ΔH°B(Bi 4 S 5 Cl 2,f,298 ) =−144,4 ± 3 kcal/mol S°(Bi 4 S 5 Cl 2,f,298 ) = 114,0 ± 4,6 cal/K·mol ΔH°B(Bi 19 S 27 Cl 3,f,298 ) = −520 ± 10 kcal/mol S°(Bi 19 S 27 Cl 3,f,298 ) = 490 ± 10 cal/K·mol ΔH°B(BiSBr f,298 ) = −40,2 ± 1,4 kcal/mol S°(BiSBr f,298 ) = 32,0 ± 3 cal/K·mol ΔH°B(Bi 19 S 27 Br 3,f,298 ) = −493,6 ± 6,7 kcal/mol S°(Bi 19 S 27 Br 3,f,298 ) = 499,8 ± 17 cal/K·mol ΔH°B(BiSI f,298 ) =−27,8 ± 1,4 kcal/mol S°(BiSI f,298 ) = 36,1 ± 2,5 cal/K·mol ΔH°B(Bi19S27I3,f,298) =−464,4 ± 15 kcal/mol S°(Bi 19 S 27 I 3,f,298 ) = 502,7 ± 15 cal/K·mol

The spectroscopic and photochromic properties of the dinuclear rhodium complex Rh 2 L 10 X 4 (L = CH 3 CN, X− = BF − 4 ) have been studied in acetonitrile solution. A reversible wavelengthdependent photoredox disproportionation of the dark-equilibrated dirhodium(II) compound occurs upon irradiation with quantum yields of φ = 0.04 at 254 nm and φ = 0.60 at 436 nm, respectively. While the photolysis products show conspicuous aggregation phenomena at higher concentrations, a straightforward pseudo-bimolecular recombination of the metastable fragments following second-order kinetics was observed in 5 × 10 −5 M solution with k = 0.18 l mol −1 s −1 at 295 K. Both spectroscopic and kinetic results are consistent with the heterolytic formation of mononuclear rhodium(I) and rhodium(III) acetonitrile complexes in the course of the photochemical reaction.

The oxonium acid [H(OEt 2 ) 2 ]+[Ti 2 Cl 9 ] − (1) was obtained by the reaction of TiCl 4 with Et 2 O in n-pentane and subsequent partial hydrolysis. Suitable single crystals of 1 were obtained by sublimation at 5° C ([H(OEt 2 ) 2 ]+[Ti 2 Cl 9 ] − , P2 1 2 1 2 1 (no. 19), Z = 4, a = 1101.08(8), b = 1328.4(2), c = 1525.0(2) pm, T = 193(2) K, 4489 independent reflections, 197 parameters, R1 = 0.049). The cation is made up from two independent Et 2 O molecules and one disordered proton on two split positions. Both ether molecules exhibit a W form, and their molecular planes include an angle of 74.1(7)°. Thus a distorted tetrahedron is formed by the four methyl carbon atoms of the two ether molecules. The distance O···O amounts to 237.7(1) pm. The proton of the cation was characterized both by 1 H NMR (CDCl 3 , T = 23 °C: δ = 11.7 ppm, w1/2 = 100 Hz) and IR spectroscopy (3120 cm −1 , ν vbr). The [Ti 2 Cl 9 ] − ion consists of two face sharing octahedra. 47 Ti and 49 Ti NMR spectra were recorded in solution (CH 2 Cl 2 , T = 23 °C: δ 49 Ti = 137 ppm, w1/2 = 175 Hz; δ 47 Ti = −124 ppm, w1/2 = 250 Hz). The absence of a signal for TiCl 4 at δ 49 Ti = 0 ppm indicates the stability of the dinuclear anion in solution.

Tri(2-thienyl)- and tri(2-furyl)phosphine and -arsine (L) have been introduced as ligands to gold(I) chloride and acetate (AuX). Structural studies have shown that in the 1:1 complexes of the type L-Au-X the gold atoms are bound exclusively to the phosphorus/arsenic centers without any intraor intermolecular approach of the donor atoms of the three heterocycles towards the metal atoms. Intermolecular aurophilic bonding is found in the crystals of the [tri(thienyl)phosphine]gold acetate complex, but is absent in crystals of the chloride complexes. The phosphines L have been quaternized with methyl iodide and the resulting phosphonium salts [LMe]I structurally characterized to provide reference data as to the preferred configurational and conformational motifs. The mass spectra of the gold complexes indicate a high stability of the dinuclear cationic species [(LAu) 2 X]+ with X = Cl, OAc for all ligands L.

The compound Cl 3 SiCH 2 OCH 3 was prepared by reacting ClCH 2 OCH 3 with the Cl 3 SiH/NEt 3 reagent. H 3 SiCH 2 OCH 3 and F 3 SiCH 2 OCH 3 were synthesized from Cl 3 SiCH 2 OCH 3 by reduction with LiAlH 4 and by fluorination with SbF 3 , respectively. The crystal structures of the low-melting compounds H 3 SiCH 2 OCH 3 and F 3 SiCH 2 OCH 3 were determined by X-ray diffraction of in situ grown crystals. Both compounds do not show any observable β -donor-acceptor interactions, but behave structurally like usual dialkylethers or silanes, as is obvious from the structural parameters in H 3 SiCH 2 OCH 3 (<SiCO 108.4(3)-109.4(3)°, <COC 111.0(4)-111.6(4)°) and in F 3 SiCH 2 OCH 3 (<SiCO 107.1(1), <COC 111.2(2)°). Earlier postulates of Si· · ·O interactions in compounds with SiCO units could thus not be confirmed on a structural basis.

Penta-O-pivaloyl-galactopyranose and tetra-O-pivaloyl-galactopyranosyl bromide after electrophilic activation reacted with 6-O-protected 2-azido-galactosides to give the precursor structures of the Thomsen-Friedenreich antigen disaccharide with high regioselectivity, but low yield.With 4,6-Obenzylidene protected 2-azidogalactosides and 2-O-pivaloyl phenylthio galactosides, T-antigen disaccharides of this type were obtained in good yields. Glycosylation reactions of 4,6-O-benzylidene protected glucosamine derivatives with O-pivaloyl protected galactosyl bromide efficiently gave lactolactosamine disaccharides. Even a thioglycoside was efficiently galactosylated by this method resulting in the formation of a disaccharide thioglycoside useful itself as a potential glycosyl donor.

(E,E,E)-1,3,5-Tris(3,4,5-trimethoxystyryl)benzene (1a) forms monoclinic crystals of the space group P2 1 /c. Incorporation of three transoid diacetyl guest molecules between the three arms leads to triclinic crystals of the space group P1. The styryl groups, originally present in a nonsymmetrical conformation, are simultaneously transformed to a C 3 arrangement. (E,E,E)-1,3,5-Tris- (3,4,5-tripropoxystyryl)benzene (1b) forms monoclinic crystals of the space group P2 1 /c. The C 3 arrangement of the styryl groups is present in the first, the unsymmetrical arrangement in the second modification. Incorporation of two acetone guests in the largest and the middle-sized angle space between the styryl arms in the unsymmetrical arrangement, leads to monoclinic crystals of the space group P2 1 /n. The third (smallest) angle space is filled with a propoxy chain of the neighboring molecule. The pure host crystals show significant deviations from planarity which are strongly reduced by the incorporation of the guest molecules.

The title compound (2b) was obtained in 7 steps from 2-phenylbenzhydrol (5). The phenyl substituent of 2b confers thermal stability to the [5]phosphaphenanthrene system by steric protection; in addition, conjugative interaction is revealed by the UV spectrum. The analogy to the corresponding arenes is briefly discussed.

In an effort to introduce N,N-dichloroarylsulphonamides of different oxidising strengths, four mono- and five di-substituted N,N-dichlorobenzenesulphonamides are prepared, characterised and employed as oxidants for studying the kinetics of oxidation of dimethyl sulphoxide (DMSO) in 50% aqueous acetic acid. The reactions show first order kinetics in [oxidant], fractional to first order in [DMSO] and nearly zero order in [H + ]. Increase in ionic strength of the medium slightly increases the rates, while decrease in dielectric constant of the medium decreases the rates. The results along with those of the oxidation of DMSO by N,N-dichlorobenzenesulphonamide and N,N-dichloro-4- methylbenzenesulphonamide have been analysed. Effective oxidising species of the oxidants employed in the present oxidations is Cl + in different forms, released from the oxidants. Therefore the introduction of different substituent groups into the benzene ring of the oxidant is expected to affect the ability of the reagent to release Cl + and hence its capacity to oxidise the substrate. Significant changes in the kinetic and thermodynamic data are observed in the present investigations with change of substituent in the benzene ring. The electron releasing groups such as CH 3 inhibit the ease with which Cl + is released from the oxidant, while electron-withdrawing groups such as Cl enhance this ability. The Hammett equation, log k obs = −3.19 + 1.05 σ , is found to be valid for oxidations by all the p-substituted N,N-dichlorobenzenesulphonamides. The substituent effect on the energy of activation, E a and log A for the oxidations is also analysed. The enthalpies and free energies of activation correlate with an isokinetic temperature of 320 K.

Chemical analysis of the brown alga Dictyota crenulata, family Dictyotaceae, collected at Easter Island, yielded a new diterpene. The structure was determined on the basis of spectroscopic evidence. The insecticidal activity of two diterpenes towards the tomato moth Tuta absolute (Povolny) was tested.

Estrones have been subjected to an addition reaction with [(4-ethynylphenyl)azo]pyrrolidine to provide 17 α-{4-[(pyrrolidin-1-yl)-azo]phenylethynyl}estra-3,17 β -diols. A subsequent iodination with iodotrimethylsilane, produced in situ from chlorotrimethylsilane and NaI, leads to 17α-(piodophenylethynyl) estra-3,17 β -diols. This reaction can also be carried out with Na 125 I to give radiolabelled estra-3,17 β -diols, which are potentially useful radiodiagnostic agents for the detection of estrogen positive breast cancer. The stability of the radiolabelled compounds is exemplified in a stability study of 3-O-methyl 17 α-(p-[ 125 I]iodophenylethynyl)estra-1,3,5(10),6-tetraene-17 β -ol in acetonitrile.

The new ternary indium-rich compound YbIrIn 5 was synthesized from the elements via an indium flux technique. A mixture with the starting composition 1:1:7 was heated at 1300 K in a tantalum tube for 6 h and cooled to room temperature at a rate of 5 K/h. The structure was refined from X-ray single crystal diffractometer data: HoCoGa 5 type, P4/mmm, a = 461.96(7), c = 740.21(15) pm, wR2 = 0.0616, 222 F 2 values, and 12 variable parameters. The iridium atoms have eight indium neighbors in square prismatic coordination at Ir-In distances of 274 pm. The square prisms are condensed via common edges forming layers which are separated by the ytterbium and further indium atoms. Ytterbium has a cuboctahedral indium coordination. The cell volume is suggestive for divalent or intermediate-valent ytterbium.

The crystal structure of tetra(propyn-1-yl)silane, Si(C≡CMe) 4 1, has revealed a completely asymmetric molecule (point group C 1 ). Since this finding concerns a single crystal, the bulk material of 1 was studied by solid-state 29 Si and 13 C MAS NMR. This confirmed the result of the X-ray analysis, and by comparison with previous NMR measurements of the tin analogue 1(Sn) it is concluded that 1 and 1(Sn) must have very similar solid-state structures which are in contrast to those known for other tetra(alkyn-1-yl)silicon and -tin compounds. The NMR data set of 1 in solution was completed by determination of the magnitude of coupling constants 1 J( 13 C, 13 C).

The compounds 5,6-dimethyl-5,6-dihydro-[1,4]diselenino[ 2,3-d][1,3]dithiole-2-thione, 5-methyl-5,6-dihydro-[1,4] diselenino[2,3-d][1,3]dithiole-2-thione and 5,6-dihydro- [1,4]diselenino[2,3-d]dithiole-2-thione were prepared and characterized analytically and spectroscopically.

The title compound crystallizes in the centrosymmetric space group I2/a. When pumped by 458 and 1064 nm laser radiation the compound gives rise to a broad luminescence band at ca. 668 and 671 nm, respectively.

{Bis(methylthio)methylene}-2,2-dimethyl-4,6-dioxo-1,3- dioxane (7) reacts with cis-1,2-diamino-1,2-dicyanoethene to give 2,2-dimethyl-4,6-dioxo-5-{2-(4,5-dicyano)} imidazolio-1,3-dioxan-5-yl-imidazolium ylide (8) as a stable crystalline solid in good yield. The crystal structure of 8 × C 3 H 6 OS is discussed.