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Co-condensation of osmium atoms with benzene gives stable Os(η6-C6H6)(η4-C6H6) whereas co-condensation of osmium atoms with mesitylene forms the dimers[(η6-C6H3Me3)Os(µ-H)2(µ-CHC6H3Me2-3,5)Os(η6-C6H3Me3)] and [(η6-C6H3Me3)Os(µ-CHC6H3Me2-3,5)Os(η6-C6H3Me3)].

The aluminium enolate derived from the iron acetyl complex [(η5-C5H5Fe(CO)(PPh3)COCH3], in contrast to the lithium enolate, undergoes highly stereoselective aldol reactions with aldehydes to generate RR,SS-β-hydroxyacyl complexes which on decomplexation liberate β-hydroxy acids or esters. Determination of the molecular structure of RR,SS-[η5-C5H5)Fe(CO)(PPh3)(COCH2CH(OH)CH2CH3] allowed assignment of the relative configuration of the new chiral centre.

Three new charge transfer salts of tetrathiafulvalene (TTF)-based donors with selenocyanate-metal complex anions have been synthesized. The salts have been characterized as BEDT-TTF[Cr(NCSe)]·CHCl , II, TTF[Cr(NCSe)phen], III and BEDT-TTF[Cr(NCSe)phen]·CHCl , IV, where phen = 1,10′-phenanthroline and BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene. At 120 K, II crystallizes in the P2/m space group with a = 10.454(1), b = 31.990(1), c = 12.339(1) A, β = 113.163(2)°, V = 3793.8 A, Z = 4 and at 240 K in the same space group with a = 10.530(1), b = 32.122(1), c = 12.396(1) A, β = 113.186(3)°, V = 3854.2 A, Z = 4. At 240 K III crystallizes in the C2/c space group, a = 38.9272(5), b = 11.2992(1), c = 15.2540(3) A, β = 106.8877(6)°, V = 6420.1 A, Z = 8. The structure of IV has been solved in the P1 space group with a = 8.7629(3), b = 11.7977(4), c = 26.6031(9), α = 81.697(2), β = 87.858(3), γ = 74.8471(14), V = 2626.8 A, Z = 2. All of the salts have numerous S⋯Se close atomic contacts between donors and acceptors but there is no magnetic exchange between ions, as previously seen in closely related salts such as TTF[Cr(NCS)phen] and (donor)[M(NCS)(isoquinoline)], where M = Cr, Fe and donor = TTF, BEDT-TTF or TMTTF (tetramethyltetrathiafulvalene). Indeed, II and IV are paramagnetic semiconductors whereas IlI is a paramagnetic insulator. The absence of long-range magnetic order is discussed in terms of structure-function relations since there are no π-stacking interactions between donor and acceptor, which are seen in all of the bulk magnets of this type where the donor spin is magnetically coupled to the anion. The synthesis and crystal structure of the starting material, [(CH)N][Cr(NCSe) ], I, is also reported; it crystallizes in the P1 space group with a = 12.220(1), b = 12.814(1), c = 13.008(1) A, α = 99.608(6), β = 114.028(5), γ = 92.637(6)°, V = 1819.5 A, Z = 2. © 2002 Elsevier Science (USA).

Preparation, crystal structure and magnetic properties of a 3,5-dimethylpyrazolate bridged binuclear copper(II) complex [Cu2(L1)(3,5 prz)] (L1 = 1,3-Bis(2-hydroxy-1-napthylideneamino) propan-2-ol) (1) are reported. Variable-temperature magnetic susceptibility measurements for a powdered sample of the complex were carried out in the temperature range 5 - 350 K and analysed to obtain values of the parameter J in the exchange Hamiltonian H = -2JS1·S2 . In the dicopper(II) complex [Cu2(L2)(3,5 prz)], (L2 = l,3-Bis(2-hydroxy-5-chlorosalicylideneamino) propan-2-ol) (2) reported recently the antiferromagnetic interaction is much less than that of 1 (-27 = 440 cm-1 ), as result which is difficult to explain in terms of structural factors on the basis of widely accepted criteria. The differences in the magnetic behaviour now have been rationalized using the “ligand orbital complementary” concept

Variable temperature single-crystal X-ray diffraction and solid-state NMR experiments have been performed on the thiourea cycloheptane (TC7), cyclooctane (TC8), and cyclooctanone (TCO8) inclusion compounds. Three different phases have been evidenced for TC7 and four for TC8, while only one phase change at high temperature has been found for TCO8. At room temperature, the cyclooctane and cycloheptane adducts exhibit the classical rhombohedral lattice (space group R3c). In these structures, the well-resolved host thiourea structure is composed of one-dimensional nonintersecting channels running along the c axis. The guest molecules, located in the center of the channels, are highly disordered as confirmed by the solid-state 13C NMR spectra. Lowering temperature leads to a monoclinic phase resulting from the distortion of the room-temperature lattice where the guest molecules still have some degrees of disorder. Refinement has been performed with a model involving two cycloalkane rings. For TC8, a supplemen...

Preparation, crystal structure and magnetic properties of a heterodinuclear complex, LCu(Me2CO)Gd(NO3)3 (L = (N,N′-bis(3-methoxysalicylidene)propane- 1,2-diamine) are reported. The crystal structure of the complex was determined by X-ray diffraction methods at 200 K. (C19H22N2O4 )Cu(C3H6O)Gd(NO3)3, monoclinic, space group P21/c, with a = 9.795(9), b = 18.763(3), c = 15.579(2) Å , β = 95.297(2) V = 2850.9(7) Å3 and Z= 4. The central region of the complex is occupied by Cu(II) and Gd(III) ions which are bridged by two phenolato oxygen atoms of the ligand. The copper ion adopts a square-based 4+1 coordination mode, the equatorial N2O2 donors being afforded by the ligand while the axial position is occupied by an oxygen atom of the acetone molecule. The Gd(III) ion is deca-coordinated. In addition to the two phenolate oxygen atoms, the coordination sphere contains two oxygen atoms of the OMe side arms of L and six oxygen atoms from the three bidentate nitrate ions. The Gd... Cu separation is 3.425(3) Å and the dihedral angle between the GdO(l)Cu and GdO(2)Cu planes is 164.8°. The magnetic susceptibility of the complex was measured over the range 5 - 350 K and the observed data were successfully simulated by the equation based on the spin-Hamiltonian operator (H = -JSCu · SGd), giving the exchange integral J(Cu-Gd) = 5.6(1) cm-1. This indicates a weak ferromagnetic spin exchange interaction. The nature of the magnetic super-exchange interaction of the title compound is compared with similar [Gd(III)-Cu(II)] heterodinuclear complexes.

Variable-temperature single-crystal X-ray experiments have been performed on the thiourea pyridinium chloride, bromide, and iodide inclusion compounds. Two phases were found for the chloride, three for the bromide, and two for the iodide. As previously reported for the bromide, at room-temperature all three halides were found to form orthorhombic crystals in space group Cmcm. For each compound, the pyridinium cation is disordered in the square cross section thiourea channels. On cooling, the chloride undergoes a phase change between 200 and 230 K to give an orthorhombic form in Pbca with the a axis doubled and the pyridinium ions partially ordered. The bromide undergoes a phase change between 170 and 165 K to a partially ordered form in space group Cmc21 with the a axis tripled. A second phase change occurs between 140 and 150 K to a fully ordered phase in space group P21cn with cell dimensions approximately the same as the room-temperature form. The iodide undergoes a single-phase transition at 120−130 K...

Preparation and magnetic properties of a 3,5-dimethylpyrazolate bridged binuclear copper(II) complex [Cu2(L)(3 ,5 -pyz)] (L = 1,3-Bis(2-Hydroxy-5-Chlorosalicylideneamino)propan- 2-ol) is reported. The crystal structure determined by X-ray diffraction methods. (C22H20N4O3CI2CU2), triclinic, space group P1̄, a = 9.622(3), b = 10.921(2), c = 11.420(3) Å, α = 100.73(2), β = 94.04(2), Υ = 108.08(2)°, V = 1110.2(5) Å3, Z = 2. Two copper(II) ions in a square-planar coordination are bridged via alkoxide oxygen and 3,5-dimethyl pyrozolate nitrogen atoms to form a dinuclear unit. The metal coordination sphere is four-coordinate, planar with an N2O2 donor set. The dihedral angle between the two coordination planes is 166.83°. There are significant intermolecular interactions between neighbouring binuclear entities. The shortest intermolecular Cu (1) ... Cu(1)i distance is 3.383(1) Å and the Cu(1) - O ( 1)i distance is 2.666(3) Å (i = 1 -x, -y, 1 - z). The variable-temperature magnetic susceptibility measurement for a powdered sample of the complex was carried out in the temperature range 5 - 350 K and analysed to obtain values of the parameter J in the exchange Hamiltonian ℋ = -2JScu Scu; 2J = -164 cm-1. The magnetic moment at 300 K is about 2.42 μB, and 0.22 μB at 5 K. The weak antiferromagnetism of the present complex is reasonably explained in terms of the orbital countercomplementary effect based on Hoffmann's theory for super-exchange interaction

The deoxycholic acid inclusion complex (DCA) 2 :ferrocene (1) undergoes a gradual phase transition above ambient temperature, completed by ∼360 K. The phase transition is characterized by using single-crystal X-ray diffraction and 13 C CP/MAS NMR spectroscopy. 13 C CP/MAS NMR spectra of 1 suggest two DCA molecules in the crystallographic unit cell, which on heating become increasingly similar, until beyond ∼345 K only one molecular type is detected. The crystal structure has been determined at 360, 294, 200, and 100 K. Single-crystal diffraction data show a similar phase change at around 350 K. At T s 294 K the structure is solved in P2 1 2 1 2 1 , and at 360 K, the a axis is halved in a high-temperature form with symmetry P22 1 2 1 . In the temperature region 320-340 K, the single-crystal X-ray diffraction structure cannot be solved adequately. The atomic displacement ellipsoids of the ferrocene molecule at the various temperatures are consistent with a wobble about the molecular 5-fold axis proposed previously from 2 H NMR studies. The transition, although most clearly observed in the positions of the deoxycholic acid molecules, is largely dominated by the dynamic behavior of the included guest ferrocene molecules. The mechanistic nature of and the similarities and differences in the way this transition is detected by NMR and XRD techniques are discussed.

A series of new charge transfer salts of electron donors based on tetrathiafulvalene, TTF, with the anion [Cr(NCS)4(phen)]~ (phen = 1,10-phenanthroline) have been prepared. Single crystal X-ray diffraction provided structures for salts with donors TTF, TMTTF, tetramethyltetrathiafulvalene, and TMTSF, tetramethyltetraselenafulvalene. The salts were found to be [TTF][Cr(NCS)(phen)] at 293 K, [TMTTF][Cr(NCS)(phen)]-CHCl2 at 250 K and rrMTSF][Cr(NCS)(phen)]2-0.5CHCl at 293 K. For the TMTSF compound the solvent is disordered at 293 K so the structure was also solved at 120 K when the solvent becomes ordered. All of the salts have multiple S ⋯S or S ⋯Se close contacts between the anions and cations. The TTF salt is a bulk ferrimagnet with Tc = 9 K and is an insulator whereas the TMTTF salt is an antiferromagnetic (TN = 3.0 K) insulator. Both have close atomic interactions of the phen-donor n-stacking type, but the TMTTF salt also contains close anion-anion contacts and dimerised cations whereas the TTF salt consists of stacks of alternating cations and anions. The TMTSF salt is a paramagnetic semiconductor and does not display n stacking but has close inter-donor Se ⋯Se contacts and isolated anions which afford the magnetic and transport properties. © The Royal Society of Chemistry 2000.

The diastereoselectivity in the alkylation of the enolates of bicyclic lactams 2 derived from pyroglutaminol 1a has been found to depend upon the nature of the hemiaminal ether protecting group. Although exo-alkylation has been widely reported for 2a,b,e, endo-alkylation is favoured for 2d. It is postulated that this is a result of the opening of the bicyclic structure of the enolate derived from 2d, and the consequent stereoelectronic facilitation of endo-facial attack. © The Royal Society of Chemistry 2000.

The complex [U{N(SiMe(3))(2)}(2){N(SiMe(3))(SiMe(2)CH(2)B(C(6)F(5))(3))}] (1) is formed in the reaction between the hydride complex [U{N(SiMe(3))(2)}(3)(H)] and B(C(6)F(5))(3), and H(2) is evolved. The X-ray [C(36)H(53)BF(15)N(3)Si(6)U.3.5C(6)D(6), triclinic, space group Po, Z = 2, 90 K, a = 14.065(1) A, b = 14.496(1) A, c = 18.759(1) A, alpha = 82.898(1) degrees, beta = 74.415(1) degrees, gamma = 62.919(1) degrees ] and neutron structure [C(36)H(53)BF(15)N(3)Si(6)U.3.5C(6)D(6), triclinic, space group Po, Z = 2, 20 K, a = 13.993(1) A, b = 14.484(1) A, c = 18.720(1) A, alpha = 82.810(1) degrees, beta = 74.200(1) degrees, gamma = 63.054(1)E] of compound 1, which crystallizes with 3.5 molecules of C(6)D(6) per asymmetric unit, show the electron deficiency of the uranium atom to be effectively compensated by the formation of multicenter bonds between U and three Si-CH(2) units of the amido ligands. The reaction of the uranium complex [U{C(Ph)(NSiMe(3))(2)}(2)(Cl)(2)] with [Na(BH(4))] gives the complex [U{C(Ph)(NSiMe(3))(2)}(2){m(3)-BH(4)}(2)] (2). The X-ray structure of 2 [C(26)H(54)B(2)N(4)Si(4)U, monoclinic, space group C2/c, Z = 4, 90 K, a = 21.613(1) A, b = 9.233(1) A, c = 18.132(1) A, beta = 98.804(1) degrees ] proves unequivocally the m(3) coordination of the BH(4) moieties. In both single-crystal X-ray structure determinations, all hydrogen and deuterium atoms could be located and isotropically refined, including those which are directly coordinated to the uranium. The reliability of the refined hydrogen and deuterium positions for compound 1 is confirmed by comparison of the X-ray and neutron structure determinations. The ability to locate the hydrogen and deuterium positions in these uranium compounds by single-crystal X-ray diffraction is due to good crystal quality, the measurement of data at low temperature, and the use of image plate technology for data collection.

5,10,15,20-Tetra(4-n-butylphenylethynyl)porphyrin has been synthesised from 4-n-butylphenylpropynal and converted into its zinc(II) and lead(II) complexes. The solution electronic spectra of these porphyrins are compared to the analogous complexes of 5,10,15,20-tetra(trimethylsilylethynyl)porphyrin. The aryl rings of the tetra(4-n-butylphenylethynyl)porphyrin extend the porphyrin chromophore, resulting in an increase in the oscillator strength and a bathochromic shift of about 600 cm-1 in all the absorption bands. Metallation with lead(II) results in a larger bathochromic shift of about 1400 cm-1, when compared with zinc(II). The crystal structure of the pyridine zinc complex of 5,10,15,20-tetra(4-butylphenylethynyl)-porphyrin shows that the molecule has a large approximately planar π-system. Pairs of diagonally off-set π-π stacked porphyrins pack into a layer structure. Each pyridine ligand is located in a pocket defined by four butyl chains.

A method for synthesising open-framework phosphates under less-severe conditions than those employed in conventional solvothermal processes is described. Two new layered aluminum phosphates contain...

13C CP/MAS NMR spectra of the free acid of phenoxymethyl penicillin (penicillin V) and of its lithium, sodium, rubidium, and cesium salts (C16H17N2O5SM, M = H, Li·H2O, Na, Rb, and Cs) have been studied at a range of temperatures between 180 and 400 K. The 13C CP/MAS NMR spectra at ambient temperature indicate that the structures have one, two, one, four, and one molecule(s), respectively, in the crystallographic asymmetric unit. This is confirmed by the known crystal structure of the free acid and the single-crystal X-ray diffraction studies reported here of the various salts. The variable-temperature 13C CP/MAS NMR spectra indicate that the phenyl rings of all the molecules perform 180° flips about their local C2 axes, with measured or extrapolated rate constants in the range 5 × 10-12 to 8 × 109 s-1 in the temperature regime 200−380 K, and spanning 11 orders of magnitude at ambient temperature. The atomic displacement parameters of the X-ray structural model suggest that these rings also undergo signifi...

The crystal structure of trans-diaquabis(methoxyacetato)copper(II), C(6)H(14)O(8)Cu, has been determined by neutron diffraction at 4.2 K (monoclinic, P2(1)/n, a = 6.88(1), b = 7.19(1), c = 9.77(2) Å, gamma = 95.7(1) degrees, (Z = 2)) and by X-ray diffraction at 125, 165, 205, 240, 265, 295, and 325 K. These measurements show that there is no phase change in the temperature range 4.2-325 K. The copper(II) coordination at 4.2 K is a tetragonally distorted elongated rhombic octahedron (Cu-OOC 1.955(1), Cu-OMe 2.209(1), and Cu-OH(2) 2.031(2) Å). As the temperature increases to 325 K, the Cu-OOC bonds shorten slightly to 1.934(5) Å, the Cu-OMe bonds shorten more markedly to 2.137(4) Å, and Cu-OH(2) lengthens to 2.155(6) Å to give a tetragonally distorted compressed rhombic octahedron. For comparison the structure of the isomorphous nickel(II) complex (monoclinic, P2(1)/n, a = 6.633(1), b = 7.192(1), c = 10.016(2) Å, gamma = 98.30(2) degrees, (Z = 2)) has been redetermined at 295 K and the structure of the analogous zinc(II) complex (orthorhombic, F2dd, a = 7.530(1), b = 13.212(1), c = 21.876(2) Å (Z = 8)) has also been determined. The nickel(II) complex has an almost regular trans (centrosymmetric) octahedral coordination (Ni-OOC 2.022(1), Ni-OMe 2.043(1), and Ni-OH(2) 2.077(2) Å). However, zinc(II) has a very distorted octahedral coordination with the zinc atom on a 2-fold axis with the water molecules and the methoxy ligators cis and the carboxylate ligators trans (Zn-OOC 1.985(1), Zn-OMe 2.304(2), and Zn-OH(2) 2.038(2) Å). The variation in the dimensions of the copper(II) coordination sphere is discussed in terms of static (low temperature) and planar dynamic (high temperature) pseudo-Jahn-Teller effects.

The transition-metal oxo complexes [VO(acac) 2 ], [{TiO(acac) 2 } 2 ] and cis-[MoO 2 (acac) 2 ] (acac = C 5 H 7 O 2 ) reacted with the strong Lewis acid B(C 6 F 5 ) 3 to give the structurally characterized complexes [V{OB(C 6 F 5 ) 3 }(acac) 2 ], [Ti{OB(C 6 F 5 ) 3 }(acac) 2 ] and cis-[MoO{OB(C 6 F 5 ) 3 } (acac) 2 ]. The MO–B moiety is essentially linear.

Prizidilol, a compound combining vasodilator and beta-blocker functionalities in the same molecule, has been synthesized and characterized by Smith Kline and French Research Ltd. Crystal data: C17H25N5O2 x 1/2H2SO4 x H2O, M(r) = 398.47, orthorhombic, a = 10.722 (2), b = 11.635 (6), c = 34.105 (3) A, V = 4254.61 A3, Pbnm (non-standard form of Pnma) (D16(2h), No. 62), Z = 8, F(000) = 1704, Dx = 1.244 Mg m-3, mu(Cu K alpha) = 11.673 cm-1, R = 0.064 for 2432 independent reflections with I > 3 sigma(I). Prizidilol shows strong conformational similarities to propranolol and is protonated at the secondary amine. The 6-phenyl-3-hydrazinopyridazine residue is not planar. The hydroxy group at the asymmetric carbon is disordered so that both enantiomers are found at each molecular site. The sulfate ions and disordered water molecules lie in the crystallographic mirror plane.

The crystal and molecular structures of the following compounds showing histamine H2-antagonist activity have been determined: (1) N-Cyano-N'-methyl-N"-12[(2-pyridyl)methylthi_'o]ethyl } guanidine, C 11H 15 N5 S, Mr = 249.33, triclinic, P1, a = 7.482(2), b -- 9.775(2), c = 10.019(1) A, a -- 116.00(1),/3 = 102.00(2), "7 = 96.78(2) °, V = 625.7A 3, Z = 2, Dx = 1.32gcm -3, A(CuKa) 1.5418 A, # = 21.21 cm -~, F(000) = 264, R = 4.98% for 2490 observed reflexions. (2) N-Cyano-N'-methyl-N"- 12[(3-methoxy-2-pyridyl)methylthio]ethyl }guanidine, C12HITNsOS, Mr = 279.36, monoclinic, P21/a, a = 8.670(4), b = 14.095(4), c = 11.682(2)A, /3 = 99.32(7) ° , V = 1408.7A 3, Z = 4, Dx = 1.32gcm -3, A(MoKa) = 0.71069 A, # -- 2.3 cm -1, F(000) --- 592, R = 3.72% for 1880 observed reflexions. (3) N-Cyano-N~-methyl-N ''- { 2[(3-bromo-2-pyridyl)methylthio]ethyl } guanidine, C11H14

The variable-temperature 13 C CP/MAS NMR spectra of the potassium salt of phenoxymethylpenicillin (C 16 H 17 N 2 O 5 SK) (potassium penicillin V) at T

The copper(II) ion is in an elogated tetragonally distorted octahedral environment in all four compounds. The ethoxyacetate ligand is unidentate in the tetraammine compound, but the hydroxy- and alkoxycarboxylate ligands from trans-planar five-membered chelate rings in the other three compounds. Cooperative variations in the dimensions of the copper(II) coordination sphere may be ascribed to the different σ donors powers of the ligand

Treatment of 3-aroyloxy- and 2-(aroyloxymethyl)tetrahydrofurans with TiCl4 results in cleavage of the heterocyclic ring with intervention by the appropriately situated ester group to form intermediates which, on work-up and hydrolysis, furnish 1,4-diols.

5-(1,3-Benzodioxol-5-ylmethyl)-2-[2-(5-methyl-1H-imidazol-4-ylmethylthio)ethylamino]-4(1H)-pyrimidone dihydrochloride C 19 H 23 N 5 O 3 S 2+ .2Cl - , M r =472.4, triclinic, P1l, a=8.291 (2), b=10.759 (3), c=13.169 (3) A, α=108.42 (2), β=93.28 (2), γ=100.3 (3) o , V=1088.6 A 3 , Z=2, D x =1.44 Mg m -3 , λ(Mo Kα)=0.7107 A, μ=0.42 mm -1 , F(000)=492, T=294 K, final R=0.038 for 3184 unique observed reflexions. All bonded distances and interbond angles lie within the range of values for compounds of a similar nature

The new compounds K[W(PMe3)3H5], [K(18-crown-6)][W(PMe3)3H5](18-crown-6 = 1,4,7,10,13,16-hexaoxacycloctadecane), Na[W(PMe3)3H5], [Na(15-crown-5)][W(PMe3)3H5], (15-crown-5 = 1,4,7,10,13-pentaoxacyclopentadecane), [{W(PMe3)3H5Li}4], K[W(η-C5H5)(PMe3)H4], [K(18-crown-6)][W(η-C5H5)(PMe3)H4], [K(18-crown-6)][W(η-C5H4Et)(PMe3)H4], K[cis-Re(PMe3)4H2], [K(18-crown-6)][cis-Re(PMe3)4H2], [W(PMe3)3H5(SnBun3)], [W(ηC5H5)(PMe3)H4(SnBun3)], [Re(PMe3)4H2(SnBun3)], [H(η-C5H5)2ZrW(PMe3)3H5], [Cl(η-C5H5)2ZrW(PMe3)3H5], [{(Ph3P)Au}3W(PMe3)3H4]Cl·xCH2Cl2 and [K(18-crown-6)][Mo(η-C5H5)2H] are reported. The X-ray crystal structures of [K(18-crown-6)][W(PMe3)3H5], [Na(15-crown-5)][W(PMe3)3H5], [{W(PMe3)3H5Li}4], [K(18-crown-6)][cis-Re(PMe3)4H2], [{(Ph3P)Au}3W(PMe3)3H4]Cl·0.15CH2Cl2 and [K(18-crown-6)][Mo(η-C5H5)2H] have been determined. The crystal structures of [K(18-crown-6)][W(PMe3)3H5] and [Na(15-crown-5)][W(PMe3)3H5] have also been determined by neutron diffraction. Evidence for the presence of a degree of covalent bonding in the systems M–H–M′, where M = W and M′= Li, Na or K and M = Re, M′= K, is discussed.

The unsupported WW bond of [W2(η-C5H4R)2X4](X = Cl, R = Pri1a or Me 1b; X = Br, R = Pri2) readily undergoes oxidative-addition reactions with HY [Y = H, Cl, SR′(R′= Me, Et, Pri, Ph or But), or PPhR′(R′= H or Ph)] to afford the corresponding derivatives [W2(η-C5H4R)2X4(µ-H)(µ-Y)] in good yields. For 1a the addition of H2 is reversible with reductive elimination occurring readily at ca. 50 °C under reduced pressure. The µ-phosphido complex [W2(η-C5H4Pri)2Cl4(µ-H)(µ-PPh2)] has been crystallographically characterised and possesses a WW double bond [2.6558(3)A]. The µ-thiolato complexes [W2(η-C5H4R)2Cl4(µ-H)(µ-SR′)] are fluxional and undergo inversion at the µ-S atom; ΔG‡ values for this process have been determined and increase in the order R′= But < Pri < Ph < Et < Me. The µ-chloro complexes [W2(η-C5H4R)2Cl4(µ-Cl)(µ-H)] undergo a different fluxional process which effectively involves rotation of the (µ-Cl)(µ-H) fragment about the W–W vector. The complexes [W2(η-C5H4Pri)2Cl4(µ-H)(µ-Y)](Y = H or PPh2) react with PMe3 to give the corresponding adducts [W2(η-C5H4Pri)2Cl3(µ-Cl)(µ-H)(µ-Y)(PMe3)], the X-ray crystal structure of the µ-phosphido complex (Y = PPh2) having been determined. In contrast, treatment of [W2(η-C5H4Pri)2Cl4(µ-H)(µ-Y)](Y = Cl or SR′) with an excess of PMe3 affords the mononuclear complex [W(η-C5H4Pri)Cl(PMe3)3].

3α,12α-Dihydroxy-5β-cholan-24-oic acid (deoxycholic acid DCA) is able to discriminate between the R- and S-enantiomers of camphorquinone and endo-(+)-3-bromocamphor and select only the S-enantiomers from a racemic mixture. DCA forms novel well ordered 1:1 adducts with (1S)-(+)-camphorquinone and (1S)-endo-(-)-3-bromocamphor, both of which have been characterized by single crystal X-ray diffraction (SXRD). When DCA is cocrystallized with (RS)-camphorquinone and (RS)-endo-3-bromocamphor, 1:1 adducts of the S-enantiomers are produced together with crystals of the free racemic guest. In contrast, in the absence of (1S)-(+)-camphorquinone, DCA forms a 2:1 adduct with (1R)-(−)-camphorquinone. In this 2:1 adduct the guest is disordered at ambient temperature and undergoes a phase change in the region 160–130 K similar to that observed for the ferrocene adduct, but with only partial ordering of the guest. The SXRD structure of the low temperature form and the variable temperature 13C CP/MAS NMR are reported. Cocrystallizing DCA with (1R)-endo-(+)-3-bromocamphor gives the free guest and a glassy solid. Chirality, 2008. © 2008 Wiley-Liss, Inc.

A common requirement in conformational analysis is the identification of a molecule's lowest energy conformations. The application of the A* algorithm to this problem is examined. The algorithm uses heuristic information about the problem domain to direct the search and has been implemented in a system for performing automated conformational analysis. The method is detailed and sample results presented. Some limitations of the approach are identified.

The method of constructing low-energy conformations using template joining can provide an efficient means of searching the conformational space of molecules. The simplest algorithm to perform this task would construct each potential conformation from scratch. However, new algorithms, some of which use techniques from Artificial Intelligence, have been developed which can greatly improve the efficiency of this approach.

An algorithm for predicting the conformations of strained molecules using Artificial Intelligence techniques is described and illustrated with some typical examples.

Treatment of 3-aroyloxy- and 2-(aroyloxymethyl)tetrahydrofurans with TiCl4 results in cleavage of the heterocyclic ring with intervention by the appropriately situated ester group to form intermediates which, on work-up and hydrolysis, furnish 1,4-diols.

The determination of small-molecule structures from single-crystal X-ray data is being carried out by researchers with little or no crys- tallographic training. At the same time, completely automatic crystal structure analysis can still only be achieved under very favourable conditions. Many of the problems that cause automatic systems to fail could be resolved with suitable chemical insight, and until this is built- in, programs continue to need human guidance. CRYSTALS version 12 contains a modern crystallographic human-interface design, and novel strategies incorporating chemical knowledge and sensible crystallographic guidance into crystal structure analysis software.

The Fourier transform of the X-ray diffraction pattern of a crystal is the electron density of the crystal averaged over space and time. In the determination of the structure of a crystal this electron density is modeled by a set of spheres of electron density representing the atoms together with a »smearing function«, the atomic displacement parameters, representing the motion (translation and libration) of those atoms. Studies of the deuterium and 13C NMR of these solids show that these XRD parameters give a less than full picture of the motional behavior in crystals. In particular XRD parameters do not give information about infrequent activated processes in the crystal or about some motional behavior related to phase changes. A number of examples of the synergy of XRD and solid state NMR will be given. These examples include phenyl ring flips in phenoxypenicillin salts, whole molecule rotations in ansatitanocene halides, guest molecule tumbling, spins and flips in thiourea clathrates cycloheptane and cyclooctane guests, cation flips and spins in thiourea pyridinium halides, wobbles, spins and phase changes in the deoxycholic acid ferrocene clathrate and motion, phase changes and chiral selectivity in the deoxycholic acid clathrates with R and S camphor, with reference to how solid state NMR gives information about the mechanism of the phase change.

5-(1,3-Benzodioxol-5-ylmethyl)-2-[2-(5-methyl-1H-imidazol-4-ylmethylthio)ethylamino]-4(1H)-pyrimidone dihydrochloride C 19 H 23 N 5 O 3 S 2+ .2Cl - , M r =472.4, triclinic, P1l, a=8.291 (2), b=10.759 (3), c=13.169 (3) A, α=108.42 (2), β=93.28 (2), γ=100.3 (3) o , V=1088.6 A 3 , Z=2, D x =1.44 Mg m -3 , λ(Mo Kα)=0.7107 A, μ=0.42 mm -1 , F(000)=492, T=294 K, final R=0.038 for 3184 unique observed reflexions. All bonded distances and interbond angles lie within the range of values for compounds of a similar nature

The complex [U{N(SiMe(3))(2)}(2){N(SiMe(3))(SiMe(2)CH(2)B(C(6)F(5))(3))}] (1) is formed in the reaction between the hydride complex [U{N(SiMe(3))(2)}(3)(H)] and B(C(6)F(5))(3), and H(2) is evolved. The X-ray [C(36)H(53)BF(15)N(3)Si(6)U.3.5C(6)D(6), triclinic, space group Ponemacr;, Z = 2, 90 K, a = 14.065(1) Å, b = 14.496(1) Å, c = 18.759(1) Å, alpha = 82.898(1) degrees, beta = 74.415(1) degrees, gamma = 62.919(1) degrees ] and neutron structure [C(36)H(53)BF(15)N(3)Si(6)U.3.5C(6)D(6), triclinic, space group Ponemacr;, Z = 2, 20 K, a = 13.993(1) Å, b = 14.484(1) Å, c = 18.720(1) Å, alpha = 82.810(1) degrees, beta = 74.200(1) degrees, gamma = 63.054(1)E] of compound 1, which crystallizes with 3.5 molecules of C(6)D(6) per asymmetric unit, show the electron deficiency of the uranium atom to be effectively compensated by the formation of multicenter bonds between U and three Si-CH(2) units of the amido ligands. The reaction of the uranium complex [U{C(Ph)(NSiMe(3))(2)}(2)(Cl)(2)] with [Na(BH(4))] gives the complex [U{C(Ph)(NSiMe(3))(2)}(2){mgr;(3)-BH(4)}(2)] (2). The X-ray structure of 2 [C(26)H(54)B(2)N(4)Si(4)U, monoclinic, space group C2/c, Z = 4, 90 K, a = 21.613(1) Å, b = 9.233(1) Å, c = 18.132(1) Å, beta = 98.804(1) degrees ] proves unequivocally themgr;(3) coordination of the BH(4) moieties. In both single-crystal X-ray structure determinations, all hydrogen and deuterium atoms could be located and isotropically refined, including those which are directly coordinated to the uranium. The reliability of the refined hydrogen and deuterium positions for compound 1 is confirmed by comparison of the X-ray and neutron structure determinations. The ability to locate the hydrogen and deuterium positions in these uranium compounds by single-crystal X-ray diffraction is due to good crystal quality, the measurement of data at low temperature, and the use of image plate technology for data collection.

Kara, Hülya (Balikesir Author), The title compound, μ-[1,3-bis(5-chloro-2- oxidobenzylideneamino)propan-2-olato(3-)]-O,N,O′:O′, N′,O″-μ-(3,5-dimethyl-pyrazolato)-N:N′-dinickel(II), [Ni2(C17H13Cl2N2O3) (C5H7-N2)], has crystallographic mirror symmetry. The Ni atoms in the dinuclear structure are linked symmetrically by the N atoms of the 3,5-dimethylpyrazole group and by the alkoxo O atom. Each NiII ion is coordinated by two N atoms and two O atoms, forming a square plane with trans-N2O2 geometry.

Two practical routes to (6S,7S)-cephalosporins from 6-aminopenicillanic acid (6-APA) are described. In the first, 6-APA was converted to (2S,4S,5S,6S)-penicillin sulfoxide 49, which underwent Morin ring expansion to a protected (6S,7S)-cephem 50. In the second, ester 15 was converted to (2S,4S,5S,6R)-penicillin sulfoxide 58, which was then transformed into (6S,7R)-cephem 59. Different methods for the epimerisation of the C-7 position of cephem 59 were examined. (C) 2000 Elsevier Science Ltd.

Photobromination of the rigid aza-bicyclic fucose mimic 3 gave a reactive glycosyl type bromide 7 as a divergent intermediate for the synthesis of both 7- O and 7- N linked bicyclic L-fucose derivatives by direct displacement with alcohols or amines. Displacement of the bromide 7 with sodium azide gave an azide 6 which on hydrogenation gave a stable monoalkyl triazene 5 , the structure of which was established by X-ray crystallographic analysis. Hydrolysis of 7 allowed access to a monocyclic L-fucose mimic with a nitrogen substituent at C-5.

A carbotricycle (13) having the same relative stereochemistry as the phorbols at 6 centres has been constructed via stereoselective Intramolecular Diels–Alder reaction of furans (IMDAF) of a precursor (7) possessing a Z-vinylogous ketoester followed by selective epimerisation at C-10 of the initial cycloadduct (11); whereas the corresponding E-isomer (8) or alkyne (3) show no stereoselection in the IMDAF.