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Sylvain Bernès

Publications and source records attributed to Sylvain Bernès.

At least 19 recordsLinked to original sources
PubMed2006

Tetrakis(pentafluorobenzenethiolato-kappaS)(triphenylphosphine-kappaP)osmium(IV): a Z' = 3 structure with a supramolecular double-stranded backbone.

The title complex, [Os(C6F5S)4(C18H15P)], crystallizes with three independent molecules in the asymmetric unit. Two of these have very similar conformations, while in the third, the axial thiolate ligand has a rotation that differs by ca 21.5 degrees . The coordination around the metal atom is trigonal bipyramidal and the supramolecular structure involves an unusual double-stranded backbone.

Journal Article↗
PubMed2005

Magnetic properties and crystal structure of a one-dimensional phase of tetrakis(mu2-benzoato-O,O')-bis(dimethyl sulfoxide)dicopper(II).

A new crystalline polymorphic phase of tetrakis(mu2-benzoato-O,O')-bis(dimethyl sulfoxide)dicopper(II) was obtained by direct synthesis, in space group P2(1)/n. The copper coordination is in a slightly distorted square pyramidal geometry with an intramolecular Cu...Cu distance of 2.6494(8) angstroms. The Cu-O distances of the two copper in a dimer are different, giving different chemical environments for each Cu ion. The crystal structure is built up of well-separated stacking columns oriented along the b-axis, with units uniformly spaced, producing a one-dimensional (1-D) zigzag chain through Cu(II)-S...S-Cu(II) interdimer interactions [S...S separation: 3.975(2) angstroms]. Magnetization measurements in the range 2-300 K indicate two magnetic orderings, at low temperature (T < 10 K) a weak ferromagnetic ordering is observed, and above this temperature an antiferromagnetic behavior takes place. ESR spectra at 300 and 77 K of a polycrystalline sample show the characteristic signal of zero-field with D = 0.354 cm(-1), consistent with a ferromagnetic Cu...Cu exchange interaction at low temperature.

Journal Article↗
PubMed2005

Conformational change induced by hydration: trans-dichlorobis[(1R,2R,3R,5S)-(-)-isopinocampheylamine]palladium(II) and trans-dichlorobis[(1S,2S,3S,5R)-(+)-isopinocampheylamine]palladium(II) hemihydrate.

The title compounds, trans-dichlorobis[(1R,2R,3R,5S)-(-)-2,6,6-trimethylbicyclo[3.1.1]heptan-3-amine]palladium(II), [PdCl2(C10H19N)2], and trans-dichlorobis[(1S,2S,3S,5R)-(+)-2,6,6-trimethylbicyclo[3.1.1]heptan-3-amine]palladium(II) hemihydrate, [PdCl2(C10H19N)2].0.5H2O, present different arrangements of the amine ligands coordinated to PdII, viz. antiperiplanar in the former case and (-)anticlinal in the latter. The hemihydrate is an inclusion compound, with a Pd coordination complex and disordered water molecules residing on crystallographic twofold axes. The crystal structure for the hemihydrate includes a short Pd...Pd separation of 3.4133 (13) A.

Journal Article↗
PubMed2005

Crystal structure, solid state and solution characterisation of copper(II) coordination compounds of ethyl 5-methyl-4-imidazolecarboxylate (emizco).

The synthesis and characterisation of the following compounds derived from the biological relevant compound ethyl 5-methyl-4-imidazolecarboxylate (emizco) (1): [Cu(emizco)Cl2] (2), [Cu(emizco)2Cl2] (3), [Cu(emizco)2Br2] (4), [Cu(emizco)2(H2O)2](NO3)2 (5) and [Cu(emizco)4](NO3)2 (6), is presented. These compounds were characterised by IR and UV spectroscopic techniques, in addition the crystal structures of compounds 1-5 were determined. For complexes 2-5, emizco is coordinated as a bidentate ligand, through the oxygen atom of the carboxylate moiety and the nitrogen atom of the imidazolic ring. Different geometries are stabilised: compound 2 includes a pentacoordinated square pyramidal metal centre, while 3-5 are derived from octahedral geometry. Halide compounds 3 and 4 show a cis-octahedral arrangement, which is not very common on [CuN2O2X2] systems, while 5 stabilises the trans-octahedral isomer. Compound 6 displays a square planar geometry. Finally, hydrolysis of emizco to its corresponding carboxylic acid (mizco), allowed the preparation of another square planar complex 7, identified as [Cu(mizco)2] 0.5H2O. Solution studies of these compounds indicate that emizco is not substituted from the coordination sphere, remaining as a bidentate ligand. Halides are substituted by water molecules, changing from cis octahedral to the trans-[Cu(emizco)2(H2O)2]2+ isomer.

Carboxylic Acids↗
PubMed2004

Conversion of [Pt(SRf)2(PPh2 -n(C6F5)n+ 1)2]( n = 0 or 1, Rf=C6HF4-4) through carbon-fluorine bond activation to [Pt(SRf)2(1,2-C6F4(SRf)-(PPh2))] and chiral [Pt(SRf)2(1,2-C6F4(SRf)(PPh(C6F5)))].

Treatment of trans-[PtCl(2)(PPh(2 - n)(C(6)F(5))(n + 1))(2)](n = 0 or 1) with Pb(SC(6)HF(4)-4)(2) yields a mixture of monometallic cis/trans [Pt(SC(6)HF(4)-4)(2)(PPh(2 - n)(C(6)F(5))(n + 1))(2)], thiolate-bridged bimetallic cis/trans [Pt(2)(mu-SC(6)HF(4)-4)(2)(SC(6)HF(4)-4)(2)(PPh(2 - n)(C(6)F(5))(n + 1))(2)] and [Pt(SC(6)HF(4)-4)(2)(1,2-C(6)F(4)(SC(6)HF(4)-4)(PPh(2 - n)(C(6)F(5))(n))].

Journal Article↗
PubMed2004

Endo-selective quenching of hexahydropyrrolo[2,3-b]indole-based N-acyliminium ions.

Radical decarboxylation of L-tryptophan-derived (2S,3aR,8aS)-8-arylsulfonyl-1,2-di(methoxycarbonyl)-1,2,3,3a,8,8a-hexahydro-2H-pyrrolo[2,3-b]indoles 8 and 9 in the presence of diphenyl diselenide results in the endo-selective formation of (2R,3aR,8aS)-8-arylsulfonyl-1-methoxycarbonyl-2-phenylselenyl-1,2,3,3a,8,8a-hexahydro-2H-pyrrolo[2,3-b]indoles 10 and 11. These selenides, in conjunction with Lewis acids, serves as precursors to the corresponding N-acyl iminium ions, which undergo selective endo-face quenching by allyltributylstannane, allyltrimethylsilane, propargyltrimethylsilane, and trimethylsilylcyanide. Stereochemical assignments rest on NMR data and crystallographic studies. The endo-selective nature of these reactions is interpreted in terms of minimization of allylic strain at the transition state for nucleophilic attack on the N-acyl iminum ion.

Journal Article↗
PubMed2004

(3aS,7aS)-1-[2-Oxo-1,3-bis[(S)-1-phenylethyl]perhydro-1,3,2lambda5-benzodiazaphosphol-2-yl]-1-phenylmethanol: a mixture of diastereoisomers in a disordered crystal.

In the title compound, C(29)H(35)N(2)O(2)P, the stereogenic C center alpha to the P atom, formed during the Pudovik condensation reaction between a deprotonated chiral diazaphosphole and benzaldehyde, has disordered substituents, giving a mixture of Calpha-R and Calpha-S diastereoisomers. Moreover, this compound crystallizes with two independent molecules in the asymmetric unit. The observed configuration at the Calpha atom is 0.741 (6)-S mixed with 0.259 (6)-R, indicating diastereoisomeric enrichment during crystallization. Data from solution and solid-state studies consistently point to an epimerization process at the Calpha atom.

Journal Article↗
PubMed2004

Chloro(histamine)(1,10-phenanthroline)copper(II) chloride monohydrate.

In the cationic complex present in the title compound, chloro[2-(4-imidazolyl-kappaN(1))ethylamine-kappaN](1,10-phenanthroline-kappa(2)N,N')copper(II) chloride monohydrate, [CuCl(C(5)H(9)N(3))(C(12)H(8)N(2))]Cl.H(2)O, the metal centre adopts a five-coordinate geometry, ligated by the two phenanthroline N atoms, two amine N atoms of the histamine ligand (one aliphatic and one from the imidazole ring) and a chloro ligand. The geometry around the Cu atom is a distorted compressed trigonal bipyramid, with one phenanthroline N and one imidazole N atom in the axial positions, and the other phenanthroline N atom, the histamine amine N atom and the chloro ligand in the equatorial positions. The structure includes an uncoordinated water molecule, and a Cl(-) ion to complete the charge. The water molecule is hydrogen bonded to both Cl(-) ions (coordinated and uncoordinated), and exhibits a close Cu.H contact in the equatorial plane of the bipyramid.

Binding Sites↗
PubMed2004

Insertion reactions of [M(SR)3(PMe2Ph)2] with CS2 (M = Ru, Os; R = C6F4H-4, C6F5). X-ray structures of [Ru(S2CSC6F4H-4)2(PMe2Ph)2], trans-thiolates [M(SR)2(S2CSR)(PMe2Ph)2] (M = Ru; R = C6F5 and M = Os; R = C6F4H-4), and trans-thiolate-phosphine [Os(SC6F5)2(S2CSC6F5)(PMe2Ph)2].

Reactions of [M(SR)(3)(PMe(2)Ph)(2)] (M = Ru, Os; R = C(6)F(4)H-4, C(6)F(5)) with CS(2) in acetone afford [Ru(S(2)CSR)(2)(PMe(2)Ph)(2)] (R = C(6)F(4)H-4, 1; C(6)F(5), 3) and trans-thiolates [Ru(SR)(2)(S(2)CSR)(PMe(2)Ph)(2)] (R = C(6)F(4)H-4, 2; C(6)F(5), 4) or the isomers trans-thiolates [Os(SR)(2)(S(2)CSR)(PMe(2)Ph)(2)] (R = C(6)F(4)H-4, 5; C(6)F(5), 7) and trans-thiolate-phosphine [Os(SR)(2)(S(2)CSR)(PMe(2)Ph)(2)] (R = C(6)F(4)H-4, 6; C(6)F(5), 8) through processes involving CS(2) insertion into M-SR bonds. The ruthenium(III) complexes [Ru(SR)(3)(PMe(2)Ph)(2)] react with CS(2) to give the diamagnetic thiolate-thioxanthato ruthenium(II) and the paramagnetic ruthenium(III) complexes while osmium(III) complexes [Os(SR)(3)(PMe(2)Ph)(2)] react to give the paramagnetic thiolate-thioxanthato osmium(III) isomers. The single-crystal X-ray diffraction studies of 1, 4, 5, and 8 show distorted octahedral structures. (31)P [(1)H] and (19)F NMR studies show that the solution structures of 1 and 3 are consistent with the solid-state structure of 1.

Journal Article↗
PubMed2003

Structure and degree of charge transfer of two polymorphs of a 1:1 molecular complex: [2,2'-bis-1,3-dithiole][9-dicyanomethylene-4,5,7-trinitrofluorene-2-carboxylic acid methyl ester] (TTF-MeDC2TNF).

A new organic charge-transfer complex, C(18)H(7)N(5)O(8).C(6)H(4)S(4), has been prepared using TTF (tetrathiafulvalene) as a donor (D) and MeDC2TNF (9-dicyanomethylene-4,5,7-trinitro-fluorene-2-carboxylic acid methyl ester) as an acceptor (A). Two monoclinic polymorphs of the 1:1 salt were crystallized and characterized by X-ray diffraction. Form alpha crystallizes in space group P2(1)/n with Z' = 1, while form beta crystallizes in space group C2/c with Z' = 1/2 and the MeDC2TNF moiety disordered across a twofold axis. Both phases have mixed-stack crystal packings, which are characteristic of semiconducting one-dimensional organic complexes. However, the observed crystal packings are significantly different, with a single D...A interlayer separation of 3.452 A for the disordered beta polymorph and interlayer separations of 3.378 and 3.483 A in the case of the ordered alpha form. These variations are reflected in the degree of charge transfer, delta, which was estimated on the basis of the b(2u) stretching-mode frequency shift observed in the IR spectra for the cyano groups of the MeDC2TNF radical anion. The fact that the charge transfer is more efficient for alpha-(TTF-MeDC2TNF) than for beta-(TTF-MeDC2TNF) (delta = 0.35 and 0.31, respectively) is consistent with the structural features observed for each crystalline form.

Journal Article↗
PubMed2003

4-(4-bromophenyl)-2-methyl-1,3-thiazole.

In the structure of the title compound, C(10)H(8)BrNS, the dihedral angles between the planes of the thiazole and aryl rings, viz. 4.2 (6) and 7.5 (6) degrees for the two independent molecules, are consistent with insignificant molecular perturbation by the weak intermolecular contacts. The molecules are close to being related by a non-crystallographic inversion centre, with C-H.pi and pi-pi intermolecular interactions observed.

Journal Article↗
PubMed2003

The triclinic polymorph of dibromo[(-)-sparteine-kappa2N,N']zinc(II).

The title compound, [ZnBr(2)(C(15)H(26)N(2))], when synthesized starting from Zn(0), is obtained in two polymorphic forms, one belonging to space group P2(1)2(1)2(1) and one to P1. The present contribution deals with the triclinic phase, which is isostructural with the orthorhombic form but presents a larger metal-metal intermolecular separation; the Zn.Zn distance is 7.4715 (6) A for the triclinic polymorph as opposed to 6.534 A for the orthorhombic polymorph.

Journal Article↗
PubMed2003

Crystal structure of trans(3R,2aS)-(-)-3-phenyl-hexahydro-oxazolo[3,2-a]pyridin-5-one.

Chiral, non-racemic hexahydro-oxazolo[3,2-a]pyridin-5-ones are strategic starting materials for the asymmetric synthesis of alkaloids, via the stereoselective C-C bond formation at the position a to the nitrogen atom. The stereoselectivity of this key step is mainly driven by the geometry of the fused rings of the oxazolopyridine moiety. In this work, the synthesis and X-ray structure of trans(3R,2aS)-(-)-3-phenyl-hexahydro-oxazolo[3,2-a]pyridin-5-one is reported.

Journal Article↗
PubMed2002

2-Methyl-1,4,5-triphenyl-1H-imidazole.

In 2-methyl-1,4,5-triphenyl-1H-imidazole, C(22)H(18)N(2), the three substituent phenyl groups are not delocalized with the imidazole moiety; the dihedral angles these phenyl groups form with the imidazole ring are in the range 25.90 (5)-63.49 (6) degrees.

Journal Article↗
PubMed2002

Supramolecular structures of metronidazole and its copper(II), cobalt(II) and zinc(II) coordination compounds.

In this work we present the synthesis and structural and spectroscopic characterization of Cu(II), Co(II) and Zn(II) coordination compounds with the antibiotic metronidazole ([double bond]emni). Coordination to metal ions is through its imidazolic nitrogen, while the hydroxyethyl and nitro groups act as supramolecular synthons. [Co(emni)(2)Br(2)], and [Zn(emni)(2)X(2)] (X(-)=Cl, Br) stabilize zig-zag chains, and a 2D supramolecular structure is formed by inter-chain contacts through inter-molecular hydrogen-bonding. Pleated sheet or layers are formed by [Co(emni)(2)Cl(2)] and [Cu(emni)(2)Cl(H(2)O)](2)Cl(2), respectively. The dinuclear Cu(II) compound [Cu(emni)mu(O(2)CMe)(2)](2) gives a one-dimensional zig-zag arrangement. The contribution of metal ions in metronidazole coordination compounds is shown in the stabilization of the different aggregate structures.

Anti-Infective Agents↗
PubMed2002

The supramolecular structure of pyridine-2,6-dicarboxylic acid.

The structure of pyridine-2,6-dicarboxylic acid, C(7)H(5)NO(4), has been determined at 0.71 A resolution. The molecule is located on a site with mirror symmetry. A one-dimensional supramolecular structure is stabilized in the solid state through a strong symmetric double hydrogen bond, with H* * *O distances of 1.86 (3) A and O-H* * *O angles of 167 (3) and 171 (5) degrees. This arrangement is similar but not identical to that reported for the isoelectronic isophthalic acid (benzene-1,3-dicarboxylic acid).

Crystallography, X-Ray↗