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The hexaethylcyclohexaarsoxane complexes [{M(CO)3}2{cyclo-(C2H5AsO)6}], M = Cr, Mo, W, 2-4 have been prepared by the reaction of (C2H5AsO)nwith the respective metal hexacarbonyl in toluene and characterized by their IR and NMR spectroscopic data. For 2 the molecular structure was established by X-ray structural analysis. The 12 atoms of the As6O6ring form a flattened cuboctahedron in which the 6 oxygen atoms lie in the central equatorial plane. Cr(CO)3groups are coordinated facially by the upper and lower three arsenic atoms. An approximately S6symmetry is displayed by the Cr2As6O6core. Average values of respectively 116.3 and 98.9° are observed for the As–O–As and O–As–O angles in the hexadentate ligand. The ΕΙ-MS and 1H NMR data for (C2H5AsO)nsuggest that this alkylcycloarsoxane is present in solution as a mixture of species including trimers and tetramers so that a metal assisted ring expansion is required for the formation of 2-4.

The stable ternary copper(II) complexes of ATP and ADP, [Cu(H2ATP)(phen)]2· 7 H2O (2) and [Cu4(HADP)2(bipy)4(H2O)2(NO3)2] · 2 NO3(3), have been isolated from aqueous solution at respective pH values of 2.8 and 4.0. Their structures have been established by single crystal X-ray diffraction. Tridentate coordination of each of the Cu atoms by ono α-, one β- and one γ-phosphate O atom of one ATP molecule is observed in 2. The binding Oαatoms occupy axial positions in a distorted octahedral geometry at Cu and the Cu- Oα interactions are weak. The other axial position is occupied by a γ-phosphate O atom of the second ATP molecule, leading to a dimeric structure. The basic structure of 3 is similar with, in this case, bidentate coordination of each of the central Cu atoms by one α- and one β-phosphate O atom of ono ADP molecule. In this case, however, the third terminal β-phosphate O atoms each bind a further Cu atom. All four Cu atoms in 3 display square pyramidal coordination. The structures of 2 and 3 are stabilised by intramolecular stacking of adenine and phenanthroline/bipyridyl systems. The significance of these structures as models for enzyme-metal ion-nucleoside polyphosphate complexes is discussed.

Compounds of the type R2PCH2PR2(R = PriO, Me2N) react with cis-LM(CO)4(L = Bicyclo[2,2,1]hepta-2,5-dien; M = Cr, Mo, W) complexes to yield cis-substituted [R2PCH2PR2]M(CO)4derivatives. The structure of the molybdenum compound, [(PriO)2PCH2P(OPri)2]Mo(CO)4, has been determined. Diphosphorus ligands of the type R2P(S)CH2PR2(R = F, PriO) are monodentate and form [R2P(S)CH2PR2]2Mo(CO)4complexes, whereas the compound (Me2N)2P(S)CH2P(NMe2)2acts as a bidentate ligand

The potentially curare-like silicon compounds 8a-8f wore synthesized and investigated with respect to their structure-activity relationships. The conformations of the com­pounds in the solid state and in solution were studied by X-ray diffraction analysis (8a-8e) and 1H NMR spectroscopy (8a-8f), respectively. The muscle relaxing properties of 8a-8f were investigated on the mouse. The observed structure-activity relationships are not in accordance with the classical “14 Å model” for neuromuscular blocking agents.

The iminovanadium (V) com pounds tC4H9N = V(NtC4H9-SiMe2-NHtC4H9)Cl2(3) and [VCl(μ-Cl)(NtC4H9)(NHtC4H9)(NH2tC4H9)]2have been prepared by reaction of Me2Si(NHtC4H9)2with VO(OC2H5)Cl2and VO(O tC3H7)Cl2, respectively. 3 was investigated by 1H , 51V NMR spectroscopy and X-ray diffraction analysis; the structure has been found to be a mononuclear vanadium complex with a distorted trigonal bipyramidal arrangement of the ligands.

Diethoxybilirubin diethyl ester crystallises triclinic P1 with a = 13.903(5), b = 17.211(7), c = 9.831(5) Å, α= 110.07(3), β = 111.22(3), γ = 69.04(3)°, Z = 2, Dx- 1.15 gcm-3. The two pyrromethene systems of the tetrapyrrole are orientated almost perpendicular to one another (interplanar angle = 91.5°). Considerable bond delocalisation is observed within the individual pyrromethene units, which contain intramolecular N-H···N hydrogen bonds of length 2.73 and 2.80 Å. Parallel stacking of the chromophores is not observed in the crystal lattice.

The reaction of But2AsCl with Na[W(CO)3Cp] in THF yields the metal arsine Cp(CO)3W−AsBut2(1), which is oxidized with elemental sulfur to the arsine sulfide Cp(CO)3W−AsBut2(S) (2). 2 is converted in refluxing pentane with loss of CO into Cp(CO)2W(η2-AsBut2S) (3). The chiral complex contains the novel dihapto-But2As−S ligand and exhibits dynamic behaviour (⊿G≠286 = 15.4 kcal/mol). Side-on coordination of the But2As−S ligand is proved by spectroscopic data and X-ray analysis. 3 crystallizes in the monoclinic space group P21/n with a = 12.141(2), b = 15.179(2), c = 19.558(2) Å, β = 99.61(2)°. The structure was refined to R = 0.051 for 4087 independent reflections.

Trichloro(purinium)zinc(II) (1) and dichloro-bis-(7-azaindole)zinc(II) (2) have been prepared from respectively 1:1 (in acid solution) and 2:1 aqueous solutions of the parent base and zinc(II) chloride. In the latter case the salt di-[7-azaindolium]zinc(II) tetrachloride (3) is isolated under acid conditions. The structures of 1-3 have been established by X-ray structural analyses. Zinc coordinates the purine nitrogen N(7) in 1 and N(3) of 7-azaindole in 2. N(l) is protonated in 1. The bond length distribution of the cations 3 suggests a significant contribution from a resonance form in which N(9) carries the positive charge

The tetramethylammonium thioarsenate(III) [Me4N]2[As6S10] (1) has been prepared together with the minor product [Me4N]2[As4S7] (2) by reaction of [Me4N]Cl with As2S3and Na2S in acetonitrile at 115 °C. The polymeric anion of 1 consists of adjacent 1∞[As3S5-] chains linked together into a 1∞[As6S102-] double chain through planar As2S2rings involving As atoms of every second constituent ring-shaped As3S6building unit. A relatively undistorted Ψ-AsS4trigonal bipyramidal geometry is observed for the participating As atoms. Individual As3S6units are linked by bridging AsS3pyramids into the zweier single chains 1∞[As4S72-] in 2.

The 2,2,5,5-tetraorganyl-1,4-dioxa-2,5-disilacyclohexanes 2a-2c were prepared by condensation of the corresponding (hydroxymethyl)diorganylsilanes 1 a-1 c. The constitution of the heterocycles was confirmed by elemental analyses, cryoscopic measurements, mass spectrometry, and NMR-spectroscopic (1H, 13C) investigations. The molecular structure of 2 b was determined by X-ray diffraction analysis.

[(μ-NtC4H9)2V2Cp2(OtC4H9)2] (2) and [(μ-Cl)2V2Cp2(NtC4H9)2] (6) have been prepared by reac­tion of LitC4H9with tC4H9N=VCp(OtC4H9)Cl and tC4H9N=VCpCl2, respectively. The molecular structure has been investigated by X-ray diffraction analysis. NMR and ESR Spectra indicate two types of tert-butyliminovanadium(IV) complexes: 2 (diamagnetic) and 6 (paramagnetic).

Re2(CO)10(1) has been photolyzed at reduced temperature in the presence of ethylene (2), styrene (3) or 2-methyl-1,3-butadiene (4), respectively. Main products of these reactions are the octacarbonyl-μ-hydrido-μ-η2:1-olefinyl-dirhenium (6, 9, 12, 13, 15) and tridecacarbonyl-μ-η2:1- olefinyl-trirhenium complexes (7, 14, 16). In lesser amounts, three isomeric undecacarbonyl-μ- hydrido-bis(μ-η2:1-vinyl)trirhenium com pounds (8 a, 8 b, 8 c), enneacarbonyl-η2-ethylenedirhenium (5) and three octacarbonyl-η4-diene-dirhenium complexes (10,17,18) are formed. The reaction products were separated by HPL chromatography. They were characterized by IR and NM R spectroscopy (1H , 13C) and by C, H elemental analyses. The molecular and crystal structure of tridecacarbonyl-η2:1-E-3-methyl-1,3-butadien-1-yl-trirhenium was determined by X-ray structure analysis.

The essential fatty acids linoleic, α-linolenic and arachidonic acid have been crystallized for the first time. The crystal and molecular structures have been elucidated by X-ray analysis. Linoleic acid crystallizes monoclinic P21/c with a = 4298(3), b = 463.2(3), c = 937.7(6) pm, β = 109.38(8)°, Z = 4. The closely packed molecules are stretched with a tttttts̄CssCs̄tt conformationa. By comparison of the unit-cell constants and calculated densities of the unsaturated fatty acids it may be shown that both α-linolenic acid and arachidonic acid also possess stretched structures in the crystal lattice, α-linolenic acid must display a tttttts̄CssCs̄s̄Cs and arachidonic acid a tts̄CssCs̄s̄CssCs̄ttt conformation.

Ethylcycloarsathiane (C2H5AsS)ncrystallizes as a crown-shaped cyclotetramer 1 from a chloroform/pyridine solution. 1H and 13C NMR studies indicate the presence of two major oligomers in CHC13solution in an approximately 1:1 ratio. Reaction of 1 with AgCF3SO3yields [Ag{cyclo-(C2H5AsS)4}2]CF3SO3(2) in which the silver (I) cation exhibits a distorted quadratic-antiprismatic coordination geometry with four shorter (2.716(7), 2.767(5) Å) and four longer (3.218(6), 3.328(9) Å) Ag-S distances. The tetraethylcyclotetraarsathiane ligand exhibits a K1S coordination mode in the complex [cyclo-(C2HsAsS)4]·2SbBr3(3) with the sulphur atom adopting an axial positon in a ψ-trigonal bipyramidal antimony coordination polyhedron

Reaction of (Et4N)Cl with AS2S3and Na2S in acetonitrile at 110°C affords the polymeric thioarsenate(III) (Et4N)2As6S10in which the cyclic [As3S6]3-and chainlike [As3S7]5-trinuclear molecular building units are linked together through common sulphur atoms into infinite double chains. In contrast, reaction of the same starting materials at higher temperatures (180°C) in water leads to formation of a markedly denser phase (Et4N)2As8S13, whose thioarsenate(III) 1∞[As8S132-] anions exhibit a higher condensation grade. These likewise double chains are composed of cyclic [AS3S6]3-and dinuclear [As2Ss]4-units with shared ѱ-AsS3tetrahedra corners. Analogous treatment of (Et4N)Cl with As2Se3and Na2Se in acetonitrile (T =110°C) yields (Et4N)[SeAsSe7].

2,2'-Bipyridine-bis(o-phenylenedioxy)phosphonium hexafluorophosphate crystallises in the monoclinic space group C2/c (Z = 8) with a = 18.654(4), b = 10.131(2), c = 24.344(4) Å, β = 99.53(4)°. The cationic phosphorus atom displays an octahedral coordination slightly distorted towards the tetrahedral one of an uncomplexed phosphonium center. The OPO bond angles are between 91.6 and 95.7(2)°, the NPN angle of the bipyridine chelate ring in contrast is only 81.7(2)°. The ring systems of the bipyridine ligand are inclined slightly to one another at an angle of 4.7°. The bond lengths to the cationic phosphorus are P - 0 1.668-1.672(3), P-N 1.896(4) and 1.898(4) Å. The hexafluorophosphate anion is disordered

tC4H9N = VCl2(NHtC4H9) and the tert-butylamine complex [tC4H9N=VCl2(NHtC4H9)(NH2tC4H9)] have been prepared by reaction of tC4H9N=VCl3with NH2tC4H9. 1H and 51V NMR data of these compounds are reported. The complex was investigated by X-ray diffraction analysis; the structure has been found to be a binuclear vanadium complex bridged by two Cl-atoms with a distorted octahedral arrangement of the ligands.

In the course of systematic investigations on sila-substituted parasympatholytics the diphenyl(2-aminoethoxymethyl)silanols 3b and 4b (and its carbon analogue 4a) were synthesized and characterized by their physical and chemical properties. In the solid state 4a and 4b form strong O-H---N hydrogen bonds, which are intramolecular (4a) and intermolecular (4b), respectively. 4a and 4b were found to be weak antimuscarinic agents (4b >4a) and strong papaverine-like spasmolytics (4a ≈4b).

A metal-assisted ring expansion from the preferred solution species (EtAsO)n, n = 3,4, to the hexameric ligand (EtAsO)6is observed for the reactions of [ReBr(CO)5], [RuCL2(Ph3P)3], RhCl3·3H2O and [Cu2CF3SO3)2(C6H6)] with ethylcycloarsoxane. Whereas two metal frag­ments are facially coordinated by the upper and lower three As atoms of a flattened As6O6cuboctahedron in both [{ReBr(CO)2}2{μ-[cyclo-(EtAsO)6]}] (1) and [Cu2{μ-[cyclo-(EtAsO)6]}(Me2PhP)2](CF3SO3)2 (4), potential ring strain restricts the reaction with the other compounds to the formation of mononuclear complexes [RuCl2{cyvclo-(EtAsO)6}(Ph3P)] (2)and [RhCl3{cyclo-(EtAsO)6}] (3) with k3As1,3,5coordination. The structures of 1 - 4 were established by X-ray structure analysis. A shift in the ν(As-O) IR absorption bands to higher wavenumbers (830 - 788 cm-1) is characteristic for (EtAsO)6complexes in comparison to those of the cyclic tetramer (781-747 cm-1).