Oligo-nuclear silver thiocyanate complexes with monodentate tertiary phosphine ligands, including novel 'cubane' and 'step' tetramer forms of AgSCN : PR3 (1:1)4.

Adducts of a number of tertiary pnicogen ligands ER(3) (triphenyl-phosphine and -arsine (PPh(3),AsPh(3)), diphenyl,2-pyridylphosphine (PPh(2)py), tris(4-fluorophenyl)phosphine (P(C(6)H(4)-4F)(3)), tris(2-tolyl)phosphine (P(o-tol)(3)), tris(cyclohexyl)phosphine (PCy(3))), with silver(I) thiocyanate, AgSCN are structurally and spectroscopically characterized. The 1:3 AgSCN : ER(3) complexes structurally defined (for PPh(3),AsPh(3) (diversely solvated)) take the form [(R(3)E)(3)AgX], the thiocyanate X = NCS being N-bound, thus [(Ph(3)E)Ag(NCS)]. A 1:2 complex with PPh(2)py, takes the binuclear form [(pyPh(2)P)(2)Ag()Ag(PPh(2)py)(2)] with an eight-membered cyclic core. 1:1 complexes are defined with PPh(2)py, P(o-tol)(3) and PCy(3); binuclear forms [(R(3)P)Ag()Ag(PR(3))] are obtained with P(o-tol)(3) (two polymorphs), while novel isomeric tetranuclear forms, which may be envisaged as dimers of dimers, are obtained with PPh(2)py, and, as further polymorphs, with PCy(3); these latter may be considered as extensions of the 'cubane' and 'step' forms previously described for [(R(3)E)AgX](4) (X = halide) complexes. Solvent-assisted mechanochemical or solvent-assisted solid-state synthesis methods were employed in some cases, where complexes could not be obtained by conventional solution methods, or where such methods yielded a mixture of polymorphs unsuitable for solid-state spectroscopy. The wavenumbers of the ν(CN) bands in the IR spectra are in broad agreement with the empirical rule that distinguishes bridging from terminal bonding, but exceptions occur for compounds that have a double SCN bridged dimeric structure, and replacement of PPh(3) with PPh(2)py apparently causes a significant decrease in ν(CN) to well below the range expected for bridging SCN in these structures. (31)P CP MAS NMR spectra yield additional parameters that allow a correlation between the structures and spectra.

Synthesis and conformation of fluorinated ß-peptidic compounds.

Experimental and theoretical data indicate that, for α-fluoroamides, the F-C-C(O)-N(H) moiety adopts an antiperiplanar conformation. In addition, a gauche conformation is favoured between the vicinal C-F and C-N(CO) bonds in N-ß-fluoroethylamides. This study details the synthesis of a series of fluorinated ß-peptides (1-8) designed to use these stereoelectronic effects to control the conformation of ß-peptide bonds. X-ray crystal structures of these compounds revealed the expected conformations: with fluorine ß to a nitrogen adopting a gauche conformation, and fluorine α to a C=O group adopting an antiperiplanar conformation. Thus, the strategic placement of fluorine can control the conformation of a ß-peptide bond, with the possibility of directing the secondary structures of ß-peptides.

Aspidospermatan-aspidospermatan and eburnane-sarpagine bisindole alkaloids from Leuconotis.

Leucofoline and leuconoline, representing the first members of the aspidospermatan-aspidospermatan and eburnane-sarpagine subclasses of the bisindole alkaloids, respectively, were isolated from the Malayan Leuconotis griffithii. The structures of these bisindole alkaloids were established using NMR and MS analysis, and in the case of leuconoline, confirmed by X-ray diffraction analysis. Both alkaloids showed weak cytotoxicity towards human KB cells.

Syntheses, structures and spectroscopy of uni- and bi-dentate nitrogen base complexes of silver(I) trifluoromethanesulfonate.

In extension of recent synthetic and crystallographic studies of adducts of silver(I) oxyanion salts with uni- and bi-dentate nitrogen-donor ligands, AgX : L (1 : n), a parallel series of complexes formed with silver(I) trifluoromethanesulfonate ('tfs', 'triflate') has been similarly defined, showing rather more divergence from tendencies established with the previous ClO(4), NO(3), F(3)CCO(2) core arrays than might be expected from basicity arguments. Thus, while silver triflate crystallised from neat base forms 1 : 2 mononuclear adducts with 2,4,6-trimethylpyridine and quinoline which comprise essentially linear two-coordinate [LAgL](+) cations, perturbed by approaches of the anions, 1 : 2 adducts obtained similarly from pyridine and 2-methylpyridine are [L(2)Ag(mu-tfs)(2)AgL(2)] dimers, with central four- and eight-membered rings arising from mu-OSO(2)CF(3) and extended mu-(O,O'SOCF(3)) anion bridging modes, respectively. With piperidine, a single-stranded polymer reminiscent of the arrays [(pip)(2)AgX](infinity/infinity), X = Cl, NCS, is formed, the triflate bridging through two of its oxygen atoms, rather than via a single atom bridge. With 2- and 4-cyanopyridine, the former a 1 : 1 adduct (being an acetonitrile solvate (MeCN coordinated)), and the latter 1 : 2, both are more complex structures in which the nitrile functionalities now coordinate weakly. The 1 : 2 adduct with 2-acetylpyridine parallels its perchlorate analogue, the ligands being bidentate in a mononuclear complex [L(2)AgOSO(2)CF(3)], while adducts of 2,9-dimethylphenanthroline and 2,2'-biquinolyl, both acetonitrile monosolvates, take the form [LAg(NCMe)]tfs. Agtfs : dpk (8 : 8)(infinity/infinity).EtOH ('dpk' = bis(2-pyridyl)ketone) is a complex polymer. The nature of the interactions is explored by way of spectroscopy (IR, NMR and ESI MS) and a density functional theory approach.

Bis(pyridine-κN){N,N-[1,1'-(pyridine-2,6-di-yl)diethyl-idyne]benzene-sulfono-hydrazonato-κO,N,N',N'',O'}nickel(II).

In the crystal structure of the title compound, [Ni(C(21)H(19)N(5)O(4)S(2))(C(5)H(5)N)(2)], the metal center is seven-coordinate, with an approximate penta-gonal-bipyramidal configuration. The Ni atom is chelated by a dianionic penta-dentate Schiff base via the pyridine N atom, the two azomethine N atoms and the two sulfonyl O atoms. The latter coordinate to Ni at different distances, viz. 2.3337 (12) and 2.7988 (12) Å. Two apically coordinated pyridine mol-ecules complete the seven-coordin-ate geometry. The dihedral angle between the two pyridine ring planes is 68.25 (6)°.

N'-[1-(5-Bromo-2-hydroxy-phen-yl)ethyl-idene]-3,4,5-trihydroxy-benzohydrazide dimethyl sulfoxide solvate trihydrate.

The benzohydrazide mol-ecule in the title compound, C(15)H(13)BrN(2)O(5)·C(2)H(6)OS·3H(2)O, is almost planar with an r.m.s. deviation for the non-H atoms of 0.078 Å. The organic mol-ecules, water and dimethyl sulfoxide solvent mol-ecules are linked by N-H⋯O, O-H⋯O and O-H⋯S inter-molecular hydrogen bonds, forming zigzag chains along the a axis. Intra-molecular O-H⋯O and O-H⋯N hydrogen bonds also occur.

Crystal structure and magnetism of a well isolated 2D-quantum Heisenberg antiferromagnet, (Quinolinium)(2)CuBr(4).2H(2)O, and its anhydrous form.

Reaction of quinoline with HBr and CuBr(2) generates a mixture of two compounds, (quinolinium)(2)CuBr(4).2H(2)O (1) and (quinolinium)(2)CuBr(4) (2) for which single-crystal X-ray structures have been solved. Compound 1 crystallizes in the monoclinic space group C2/c as layers of tetrabromocuprate ions which are separated by intervening layers of quinolinium ions. Compound 2 crystallizes in the triclinic space group P1. Magnetic data analysis reveals that 1 behaves as a 2D-quantum Heisenberg antiferromagnet with 2J/k(B) = -6.17(3) K within the layers. High field magnetization data at low temperatures suggests that T(N) must be less than 1.8 K for 1, yielding a figure of merit |k(B)T(N)/2J| < 0.29, which indicates excellent isolation between the layers. Magnetic exchange in compound 2 was much weaker and was fit to a linear chain antiferromagnet with 2J/k(B) = -1.59(3) K.

Leucophyllidine, a cytotoxic bisindole alkaloid constituted from the union of an eburnan and a new vinylquinoline alkaloid.

A cytotoxic bisindole alkaloid possessing an unprecedented structure constituted from the union of an eburnan half and a novel vinylquinoline alkaloid has been isolated from Leuconotis griffithii. The structure was established by analysis of the spectroscopic data and confirmed by X-ray diffraction analysis. A possible biogenetic pathway to the novel quinolinic coupling partner is presented from an Aspidosperma precursor.

Bis[4-(dimethyl-amino)pyridinium] tetra-bromidobis(4-chloro-phen-yl)stannate(IV)-4-bromo-chloro-benzene (1/1).

In the title compound, (C(7)H(11)N(2))(2)[SnBr(4)(C(6)H(4)Cl)(2)]·C(6)H(4)BrCl, the Sn(IV) atom in the tetra-bromidobis(4-chloro-phen-yl)stannate(IV) anion lies on a centre of inversion. The distances between the 4-(dimethyl-amino)pyridinium N atom and the Br atoms of the anion are 3.450 (2) and 3.452 (2) Å, suggesting weak hydrogen bonding. The 4-bromo-chloro-benzene solvent mol-ecule, which is a bromination by-product from the reaction, is disordered about a twofold rotation axis with approximately equal occupancy.

Bis[4-(dimethyl-amino)pyridinium] tetra-bromidobis(4-methyl-phen-yl)stannate(IV).

In the title compound, (C(7)H(11)N(2))(2)[SnBr(4)(C(7)H(7))(2)], the tetra-bromidobis(4-methyl-phen-yl)stannate(IV) anion possesses a centre of inversion located at the Sn(IV) atom. In the crystal structure, two inversion-related cations are linked to the anion via weak N-H⋯Br hydrogen bonds.

2-(1,3-Benzoxazol-2-ylsulfan-yl)-1-phenyl-ethanone.

In the title compound, C(15)H(11)NO(2)S, a new thio-benzoxazole derivative, the dihedral angle between the benzoxazole ring and the phenyl ring is 9.91 (9)°. An inter-esting feature of the crystal structure is the short C⋯S [3.4858 (17) Å] contact, which is shorter than the sum of the van der Waals radii of these atoms. In the crystal structure, mol-ecules are linked together by zigzag inter-molecular C-H⋯N inter-actions into a column along the a axis. The crystal structure is further stabilized by inter-molecular π-π inter-actions [centroid-centroid = 3.8048 (10) Å].

2-(1,3-Benzothia-zol-2-ylsulfan-yl)-1-phenyl-ethanone.

In the mol-ecule of the title compound, C(15)H(11)NOS(2), the 1,3-benzothia-zole ring is oriented at a dihedral angle of 6.61 (6)° with respect to the phenyl ring. In the crystal structure, inter-molecular C-H⋯O inter-actions link the mol-ecules in a herring-bone arrangement along the b axis and π-π contacts between the thia-zole and phenyl rings [centroid-centroid distance = 3.851 (1) Å] may further stabilize the structure.

(E)-3-(6-Nitro-benzo[d][1,3]dioxol-5-yl)-1-(2,4,6-trimethoxy-phen-yl)prop-2-en-1-one.

In the mol-ecule of the title compound, C(19)H(17)NO(8), the benzodioxole unit is oriented at a dihedral angle of 61.45 (6)° with respect to the meth-oxy-substituted phenyl ring. The nitro group is not co-planar to the benzene ring to which it is attached, making a dihedral angle of 31.86 (17)°. In the crystal structure, inter-molecular C-H⋯O inter-actions link the mol-ecules into chains through R(2) (2)(8) ring motifs. The π⋯π contacts between the benzodioxole rings, [centroid-centroid distances = 3.7610 (9), 3.6613 (9) and 3.7975 (9) Å] may further stabilize the structure.

A second monoclinic polymorph of 2-(diformyl-methyl-idene)-3,3-dimethyl-2,3-dihydro-1H-indole.

The crystal structure of the title compound, C(13)H(13)NO(2), is a polymorph of the structure first reported by Helliwell et al. [Acta Cryst. (2006), E62, o737-o738]. It is also monoclinic (space group P2(1)/c), but with completely different cell constants. The mol-ecular conformations of these polymorphs differ by a 180° rotation of one formyl group. The present mol-ecule is planar [maximum deviation 0.089 (2) Å] with the exception of the two methyl groups which lie on either side of the plane. There are strong intra- and inter-molecular N-H⋯O hydrogen bonds. The latter link pairs of mol-ecules across crystallographic centers of symmetry. Two aldehyde O atoms are brought close together [2.896 (4) Šin this arrangement but are not hydrogen bonded. In the earlier polymorph, one formyl group is rotated by 180° to yield inter-molecular hydrogen bonding and an infinite polymeric chain. The other formyl group is involved in the same intra-molecular hydrogen bonding as has been found here.

3,4,5-Trihydr-oxy-N'-(1H-indol-2-ylmethyl-idene)benzohydrazide-1H-indole-2-carbaldehyde azine-methanol (2/1/2).

The title compound, 2C(16)H(13)N(3)O(4)·C(18)H(14)N(4)·2CH(4)O, was crystallized from the reaction between 3,4,5-trihydroxy-benzoyl-hydrazine and indole-2-carbaldehyde in a mixture of ethanol and methanol. The compound is a stoichiometric 2:1 cocrystal of the methanol-solvated reaction product, 3,4,5-trihydr-oxy-N'-(1H-indol-2-ylmethyl-idene)benzohydrazide and 1H-indole-2-carbaldehyde azine that arose unexpectedly during the synthesis. The former mol-ecules are linked by O-H⋯O hydrogen bonds and also by π-π stacking inter-actions between benzoyl-hydrazide rings into a two-dimensional network. The methanol solvent mol-ecules are hydrogen bonded to this network. The centrosymmetric azine mol-ecules are not engaged in hydrogen bonding.

2-(Benzo[d]thia-zol-2-ylsulfon-yl)-1-(4-bromo-phen-yl)ethanone.

In the title mol-ecule, C(15)H(10)BrNO(3)S(2), the dihedral angle between the benzothia-zole ring system and the benzene ring is 67.57 (12)°. The crystal structure is stabilized by weak inter-molecular C-H⋯O inter-actions. In addition, there is an inter-molecular Br⋯C [3.379 (3) Å] contact which is shorter than the sum of the van der Waals radii of these atoms.

catena-Poly[[triphenyl-tin(IV)]-µ-2-[(3,5-di-tert-butyl-4-hydroxy-benz-yl)sulfan-yl]acetato-κO:O'].

The title compound, [Sn(C(6)H(5))(3)(C(17)H(25)O(3)S)](n), comprises two symmetry-independent five-coordinated triphenyl-tin mol-ecules which are linked by carboxyl-ate bridges into a polymeric chain. The Sn(IV) atom is in a distorted trans-C(3)SnO(2) trigonal-bipyramidal geometry. The presence of two bulky tert-butyl groups on the benzene ring prevents any hydrogen-bonding inter-actions involving the hydroxyl substituents.

N'-(2,4-Dimethoxy-benzyl-idene)-3,4,5-trihydroxy-benzohydrazide ethanol solvate.

The title compound, C(16)H(16)N(2)O(6)·C(2)H(5)OH, was synthesized from 3,4,5-trihydroxy-benzoyl-hydrazide and 2,4-dimethoxy-benzaldehyde in ethanol. The compound is not planar, with the two aromatic planes of the two aromatic rings twisted by 15.6 (1)°. The hydr-oxy groups are involved in both intra-molecular O-H⋯O and inter-molecular O-H⋯N and O-H⋯O hydrogen bonds and a C-H⋯O interaction also occurs.

3,4,5-Trihydr-oxy-N'-[(1-methyl-1H-indol-2-yl)methyl-idene]benzohydrazide.

The structure of the title compound, C(17)H(15)N(3)O(4), displays inter-molecular O-H⋯N and O-H⋯O hydrogen bonding between adjacent mol-ecules. Intra-molecular O-H⋯O hydrogen bonds also occur. The molecule is essentially planar with a deviation of 0.090 (1) Šfrom the best plane running through the connected ring systems.

2-{3-Cyano-5,5-dimethyl-4-[4-(pyrrol-idin-1-yl)buta-1,3-dien-yl]-2,5-dihydro-furan-2-yl-idene}malononitrile dichloro-methane solvate.

The structure of the title compound, C(18)H(18)N(4)O·CH(2)Cl(2), was solved using data collected from a multiple crystal (note high R factors). The crystal structure is dominated by two bifurcated attractive C-H⋯N(cyano) inter-actions.