Volume 45, Issue 10

Redetermination of the crystal structure of Cs 2 MnF 5 · H 2 O (space group Cmm 2, Z = 2, a = 974.0(2), b = 867.4(1), c = 426.0(1) pm, R = 0.026 for 478 reflections) revealed ordered instead of disordered positions of water molecules indicating ferroelectric properties. The dehydration of a twinned crystal gave an untwinned single crystal of Cs 2 MnF 5 by a topotactical reaction. The crystal structure of Cs 2 MnF 5 (space group P4/mmm, Z = 1, a = 642.0(1), c = 422.9(1) pm, R = 0.034 for 175 reflections) shows trans-connected octahedral chains [MnF 5 ] ∞ 2- with 180° Mn-F-Mn bridge angles like in the monohydrate. The bridging bonds in Cs 2 MnF 5 · H 2 O and in Cs 2 MnF 5 resp. are elongated by the Jahn-Teller effect (mean values Mn-F bridge 213/211, Mn-F term 184/186 pm). Cs 2 MnF 5 represents the “aristotype” of the so- called Tl 2 AlF 5 type structure family

The title compound is formed as a by-product in the synthesis of tetrakis[bis(trimethylsilyl)methyl]dialane(4) from potassium and chloro-bis[bis(trimethylsilyl)methyl]alane or by addition of KCl to the starting alane. 1 is a monomer in benzene solution, but a polymer in the solid state with chains formed via potassium-chlorine bridges. An interaction between a C-H σ-bond of one trimethylsilyl group and each potassium ion has also been detected

The compounds Sb 2 Br 6 (SPPh 3 ) 2 (1), Sb 2 I 6 (SePPh 3 ) 2 ·2CH 2 Cl 2 (2), and Sb 4 Br 12 (SPMe 2 Ph) 4 (3) were prepared in nearly quantitative yield by reacting of SbBr 3 or SbI 3 with the corresponding thio- or selenophosphoranes in dichloromethane solution. The reaction of SbBr 3 and Ph 4 PBr in acetonitrile solution yields (Ph 4 P) 2 Sb 2 Br 8 · CH 3 CN (4). The crystal structures of compounds 1-4 were determined from single crystal X-ray diffraction data. 1: monoclinic, space group P2 1 /n with a = 875.3(1), b = 1366.0(1), c = 1837.0(1) pm, β = 100.28(1)°, V = 2161.1 × 10 6 pm 3 and Z =2. 2: monoclinic, P2 1 /n, a = 1021.6(4), b = 1285.7(4), c = 2088.8(6) pm, β = 96.45(3)°, V = 2726.4 × 10 6 pm 3 , Z = 2. 3: monoclinic, P2 1 /n, a = 1180.5(1), b = 1407.9(1), c = 1891.5(2) pm, β = 106.35(2)°, V = 3016.6 × 10 6 pm 3 , Z = 2. 4: monoclinic, C 2/c, a = 2213.1(2), b = 1387.5(1), c = 1955.6(1) pm, β = 112.33(1)°, V = 5523.2 × 10 6 pm 3 , Z = 4. 1,2 and the anion of 4 contain centrosymmetric dimeric units with bridging halogen atoms. In all three compounds weak interactions between antimony and phenyl groups complete the sixfold coordination of Sb(III) (Sb-C: 339-365 pm). The crystal structure of 3, however, exhibits tetramers [SbBr 3 (SPMe 2 ,Ph)] 4 with bridging halogen and sulfur atoms, and without Sb-phenyl contacts. The conclusion from the different structures is that there is only a minor structural influence of the observed weak interactions

The reactions of alkali metal 2,4,6-tri-tert-butylphenoxides with trichlorosilane and silicon tetrachloride give the bis(2,4,6-tri-tert-butylphenoxy)silanes 3 and 4. Treatment of 3 and 4 with methanol in the presence of ethyldiisopropylamine yields the methoxy derivatives (ArO) 2 Si(OMe)Cl (5) and (ArO) 2 Si(OMe)H (6). Tris(2,4,6-triisopropylphenylthio)silane (9) and tris(2,4,6-tri-tert-butylphenylthio)silane (10) are formed by a similar route. The X-ray structure analysis of the extremely crowded compound 10 reveals no significant deviations from the properties of sterically less hindered arylthiosilanes. The planes of the phenyl rings are rotated by ca. 60° against one another resulting in an efficient shielding of the Si- H bond. Efforts to generate silicenium ions from 5, 6, 9, and 10 remained unsuccessful as yet

Diazadienes RN = CR′-CR′ = NR (DAD) form molecular complexes with copper(I) halides of composition (DAD)CuX, the structures of which vary from [(DAD) 2 Cu] + (CuCl 2 )⁻ with a non-tetrahedral bis(chelated) cation, over [(DAD)CuCl] 2 with asymmetrically bridging chloro ligands to planar three-coordinate (DAD)CuCl. The composition of the isolated complexes depends on the relative concentrations or on the solvent. The “soft” coordination geometry of copper is underlined by the structure of the coordination polymer of composition (DAD) 2 Cu 5 Cl 5 , in which Cu atoms of coordination number 2, 3 and 4 and very irregular geometries are encountered and where the DAD ligands are exclusively bridging. Halide ions and sp 2 -nitrogen donors are very competitive. Bridging DAD ligands are also encountered in (DAD)Cu-Y with the less nucleophilic anions trifluoromethane-sulphonate or perchlorate. Crystal and molecular structures are established for all these coordination geometries and the causes are discussed for the coordination flexibility of copper(I)

The new ligands (Me 3 Si) 2 NC(4-CF 3 C 6 H 4 )NP(Ph) 2 N(SiMe 3 ) (2) and (Me 3 Si) 2 NC(4-Me 2 NC 6 H 4 )NP(Ph) 2 N(SiMe 3 ) (3) have been prepared from 4-CF 3 C 6 H 4 CN or 4-Me 2 NC 6 H 4 CN, respectively, with LiN(SiMe 3 ) 2 , Ph 2 PCl and Me 3 SiN 3 . In solution, 2 as well as 3 form two isomers. Their structures (2a, 2 b and 3a, 3b) were tentatively assigned on the basis of NMR investigations. Crystals of 2 a and 3a are triclinic, space group PĪ. Bond lengths and bond angles of 2a and 3a are very similar. The influence of the para-substituents on the bonding properties are found to be negligible

We have investigated the high pressure behaviour of Na 3 As by powder X-ray diffraction. At 3.6 GPa the material undergoes a reversible phase transition from the Na 3 As structure (P 6 3 /mmc, a = 487.4(8) pm, c = 851.5(20) pm, Z = 2, at 3.6 GPa) to the Li 3 Bi structure type (Fm 3̅ m, a = 683.5(15) pm, Z = 4, at 3.6 GaP). The equation of states is given for the pressure range up to 26 GPa. Results are discussed with respect to structural properties of related A 3 I B V -compounds

[VCl 2 (15-crown-5)] + [VOCl 4 ] - has been prepared by the reaction of VCl 4 with 15-crown-5 in acetonitrile solution in the presence of water, forming black-brown single crystals. They were characterized by IR spectroscopy as well as by an X-ray structure determination. Space group Pnma, Z = 4, 1530 observed unique reflexions, R = 0.052. Lattice dimensions at -120°C: a = 1128.5(4), b = 1063.3(3), c = 1680(1) pm. The compound forms ions, in which the cation contains vanadium(+III), which is seven coordinate by the five oxygen atoms of the crown ether molecule and by two chlorine atoms in axial positions of a pentagonal bipyramide. The [VOCl 4 ] - anion contains vanadium (+V) with approximately tetragonal symmetry

In the reaction with hexamethyldisilthiane the cyclic trichlorophosphorane O=C(NMe) 2 PCl 3 (1) was converted to the new compound O=C(NMe) 2 P(=S)Cl (2). A range of derivatives, O=C(NMe) 2 P(=S)Y (Y=NR 2 , OMe, SMe, 3-7) was obtained in the reaction of 2 with the appropriate trimethylsilyl derivatives, Me 3 SiY. The compounds 8 and 9 (Y=NPh 2 and N(C 6 H 11 ) 2 ) could not be synthesized by this route as the required trimethylsilyl derivative was not reactive enough (Me 3 SiNPh 2 ) or was not available (Me 3 SiN(C 6 H 11 ) 2 ), presumably on account of the bulk of the NPh 2 and N(C 6 H 11 ) 2 groups. 8 and 9 could be prepared by an alternative route, i. e. by addition of elemental sulphur to the λ 3 P-diazaphosphetidinones, O=C(NMe) 2 PNR 2 (R=Ph, C 6 H 11 ), 10 and 11. Identity and structure of the new compounds were established on the basis of their elemental analyses and 1 H, 13 C and 31 P NMR studies

The reaction of the tetrachlorophosphoranes RPCl 4 (R=Me, Ph) with N,N′-dimethylurea (dmh) (1), or of the diazaphosphetidinone O=C(NMe) 2 PR (R=CCl 3 ) (3) and chlorine with N,N′-bis(trimethylsilyl)-N,N′-dimethylurea (2) furnished the spiro compounds RP[(NMe) 2 C=O] 2 (7-9). The dichlorophosphoranes O=C(NMe) 2 PRCl 2 (4-6) are intermediates in these reactions; 4 and 6 were isolated but 5 could not be obtained pure. In the reaction of 4 with 2 a mixture of products was formed, from which the novel tricyclic diphosphorane 1,3,4,6,7,9,10-heptamethyl-5-oxa-1,3,7,9,10-pentaaza-4 λ 5 ,6 λ 5 -diphosphadispiro-[3.1.3.1]decane-2,8-dione (10) was isolated in low yield. Its identity and structure were established by 1 H, 13 C and 31 P NMR spectroscopy and by a single crystal X-ray structure determination, which confirmed the presence of the novel oxazadiphosphetidine ring. 10 crystallizes in C2/c with a = 1321.1(3), b = 687.6(1), c = 1674.5(3) pm, β= 103.30(2)° and Z = 4; R = 0.039 for 1437 unique observed reflections. A crystallographic twofold axis passes through the Me-N···O moiety of the central ring

The triply bonded octahalogenodiosmate(III) anions [Os 2 X 8 ] 2- , previously known with X = Cl, Br, have now been extended to include the iodide with two staggered OsI 4 units. This compound was prepared by treating [Os 2 Cl 8 ] 2- with Nal at room temperature in acetone solution. The structure determination by X-ray diffractometry on single crystals of (PPN) 2 [Os 2 I 8 ] · 2 CH 2 Cl 2 , reveals crystallization in the monoclinic system, space group P2 1 /c with Z = 4. The Os-Os triple bond is with 2.212(1) Å the longest within the three octahalogenodiosmates(III). The Raman spectra show ν(OsOs) at 285, [Os 2 Cl 8 ] 2- ; at 287, [Os 2 Br 8 ] 2- and for the iodo compound at 270.1 cm -1 with up to three overtones. The spectroscopic constants are calculated to be ω 1 = 270.9 cm -1 ; X 11 = -0.50 cm -1 . The 10 Κ UV-VIS spectra of solid [(n-C 4 H 9 ) 4 N] 2 [Os 2 X 8 ] exhibit δ-π* transitions with maxima at 723, 690 and 643 nm, superimposed by vibrational fine structures with long progressions of 195, 211 and 183 cm -1 for X = Cl, Br, I, respectively. Oxidation of [Os 2 X 8 ] 2- , X = Cl, Br with the corresponding halogen leads to the cleavage of the Os-Os bond, and the dekahalogenodiosmates(IV), [Os 2 X 10 ] 2- , are formed

The reactions of the solvated electron, the H atom, the OH radical and the superoxide radical anion with t-butylhydroperoxide (t-BuOOH) have been studied in aqueous solutions using γ-radiolysis and pulse radiolysis to generate these radicals. The solvated electron reacts rapidly with t-BuOOH (k=5 × 10 9 dm 3 mol -1 s -1 ) yielding t-BuO· and ·OH in a ratio of 4:1. The yield of t-BuO· has been determined by measuring its fragmentation product, acetone. The H atom reacts more slowly with t-BuOOH (k=5 × 10 7 dm 3 mol -1 s -1 ). There is very little H-abstraction from the methyl and the hydroperoxyl groups (about 3%), the main reaction again being the scission of the hydroperoxyl function with a branching ratio t-BuO·/·OH of about unity. The OH radical reacts with t-BuOOH considerably more slowly (k=8 × 10 7 dm 3 mol -1 s -1 ) than with t-butanol (k=5 × 10 8 dm 3 mol -1 s -1 ) with an approximate preference of 8:1 of abstracting a methyl hydrogen over a hydroperoxyl hydrogen atom. The carbon-centered radical undergoes γ-cleavage (k ≈ 10 2 s -1 ) thereby reforming an OH radical. The resulting chain reaction is rather short (maximum yield G(2-methyl-1,2-epoxypropane), 26 × 10 -7 mol J -1 at low dose rate) due to H-abstraction at the hydroperoxyl function of t-BuOOH by the OH radical. The superoxide radical anion also reacts with t-BuOOH by cleaving the hydroperoxyl function. Its reactivity is, however, rather low (k=5 dm 3 mol -1 s -1 )

The iron(III) complex with 2-(2-benzimidazolyl)phenol (abbreviated as H(L 2 )), Fe(L 2 ) 2 (NO 3 ), and its benzoxazole derivative, exhibit highly anisotropic ESR signals in the range g = 3.6-7.2; these spectral properties differ from those of regular six-coordinate iron(III) species, but are very similar to those observed for the enzyme-competitive inhibitor complexes in protocatechuate 3,4-dioxygenase. These iron(III) compounds show negligible activity for oxidative cleavage of 3,5-di-tert-butylcatechol

The structures of two new pyoverdins (GM-I and GM-II) isolated from the culture medium of Pseudomonas fluorescens have been elucidated by spectroscopic methods and degradation studies. The pyoverdins consist of a chromophore which could be identified as (1 S)-5-amino-2,3-dihydro-8,9-dihydroxy-1 H-pyrimido[1,2-a]quinoline-1-carboxylic acid substituted at the amino group with a 3-carboxypropanoyl or a succinamoyl residue and at the carboxy group with the N-terminus of D-Ala-D-Lys-Gly-Gly-D-threo-(OH)Asp-D-Glu-D-Ser-L-Ala-D-Ala-D-Ala-L-Ala-L-N 5 -(OH)Orn. According to the “short-hand” nomenclature proposed in [2]*** the two compounds should be characterized as pyoverdin-Q-akGGd'qsAaaAO′*-SUCA and pyoverdin-Q-akGGd'qsAaaAO′ *-SUC

A new ternary phase LiPd 2 Tl has been synthesized. It crystallizes in a modified tetragonal Al 3 Ti-type-structure with the lattice constants a = 413.7(1) pm, b = 731.8(2) pm

The azoniaboratacyclopentene [-N(tBu)=B{N(tBu)SiMe 3 }-CH 2 -CH(C 2 H 3 )-ZrCp 2 -] (1) is formed from the iminoborane Me 3 Si(tBu)N··̲·B··̳· NtBu and (butadiene)zirconocene Cp 2 Zr(C 4 H 6 )

Marginalin, a product previously isolated from the pygidial glands of the water-beetle Dytiscus marginalis (Coleoptera), strongly reacts in vitro to form complexes with polyamines of biological interest. With spermin and spermidin, this interaction is specific giving 1:1 complexes which were isolated and studied (physico-chemical data). The results so far observed are discussed in relationship with the known biological properties of spermin and spermidin and the significance of marginalin in the defensive secretion of the beetle

Red crystals of the title compound have been prepared from pyridine, potassium dithiosquarate and copper(II) sulfate in water at pH 5. 1 contains an infinite zigzag chain of Cu I atoms, which extends orthogonally through a stacked structure formed by pyridinium and dithiosquarate ions. The Cu I atoms are tetrahedrally and trigonally coordinated by sulfur atoms. The Cu···Cu distances are 257.3(8), 262.1(8) and 276.4(8) pm. Crystal data: triclinic, space group P 1̄, a = 7.92(2), b = 10.52(2), c = 14.39(2) pm, α = 102.5(2), β = 104.1 (2), γ = 100.6(2)°, V = 1100.34 nm 3 , Ζ = 4; 3102 reflections, R = 0.103

The phosphonous dichlorides, PhPCl 2 and PhCH 2 PCl 2 , react with the (Z)-ketoenol CF 3 C(O)CH=C(OH)CF 3 to yield tricyclic trialkoxyphosphoranes, whose structures were determined on the basis of the 1 J PC values and “through-space” F···F coupling