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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.