Synthesis, properties, and X-ray crystal and molecular structures of homoleptic alkenyls of tin and chromium

Reaction of Li(CPhCMe2) with SnCl4 or CrCl3·3thf (thf = tetrahydrofuran) affords the isoleptic compounds Sn(CPhCMe2)4 or [Cr(CPhCMe2)4] respectively. The mode of formation and chemical properties are reported for the chromium species, and the structures of the new compounds, both of which have been determined by single-crystal X-ray analysis, are described.

Alkenyl derivatives of the metals. Oxidative addition to intermediate tin(II) alkenyls; isolation, and crystal and molecular structure of n-butyltris(triphenylethenyl)tin(IV)

Reaction of tin(II) chloride with Li(CPhCPh2) at –78 °C in diethyl ether–hexane–tetrahydrofuran affords a deep red solution whose colour fades on warming, and which we believe contains the (unstable) first dialkenyltin(II) species. The latter survives long enough at low temperatures to undergo intermolecular oxidative addition, and one such adduct leads ultimately to the formation of Sn(CPhCPh2)3Bun, which has been fully characterised including a crystal and molecular structure study. The mechanism of formation of the final product has been examined and results are reported.

Spectroscopic properties of alkenylferrocenes; crystal and molecular structure of (Z)-(1,2-diphenylethenyl)ferrocene

Studies of the 1H n.m.r. and electronic spectra of a series of alkenylferrocenes including (E) and (Z) stereoisomers of various styrylferrocenes, have provided methods of structure elucidation. Crystals of the title compound are monoclinic, space group P21/c with Z= 4 in a unit cell of dimensions a= 17.603(2), b= 10.218(2), c= 10.072 Å, β= 103.27(2)°. The structure has been determined by the heavy-atom method from diffractometer data and refind by full-matrix least-squares techniques to R= 0.043 for 2 219 unique reflections.

Synthesis and X-ray crystal and molecular structure of tetrakis(2,2-dimethyl-1-phenylethenyl)chromium(IV), the first structurally-characterised homoleptic alkenyl compound of a transition metal

The title compound, the first homoleptic Group 6A metal alkenyl, has been prepared from CrCl3·3(thf), and its properties, including X-ray crystal structure determination, are reported.

Unsaturated σ-hydrocarbyl transition-metal complexes. Part 4. Crystal and molecular structure of trans-chlorobis(diethylphenylphosphine)-(phenylethynyl)platinum(II) and comments on the relative trans influence of various carbon ligands

The molecular structure of trans-[PtCl(CCPh)(PEt2Ph)2] has been determined by X-ray diffraction methods. The crystals are monoclinic, space group P21, with a= 12.359(3), b= 13.015(3), c= 9.031(2)Å, β= 101.65(2)°, and Z= 2. The structure has been solved by the heavy-atom method and refined by full-matrix least squares to R 0.046 for 1 877 diffractometric intensity data. The crystals contain discrete molecules in which the platinum coordination is square planar. The phenylethynyl group is non-linear, with a Pt–CC angle of 163(2)°. Selected bond lengths are Pt–Cl 2.407(5) and Pt–C 1.98(2)Å. The structural trans influences of CCPh, CHCH2, and CH2SiMe3 ligands in platinum(II) complexes are compared; there is only a small dependence on hybridization at the ligating carbon atom.

Unsaturated σ-hydrocarbyl transition-metal complexes. Part 3. Crystal and molecular structure of trans-chlorobis(diethylphenylphosphine)(vinyl)platinum(II)

The molecular structure of trans-[PtCl(CHCH2)(PEt2Ph)2] has been determined by X-ray diffraction methods. The crystals are orthorhombic, space group Pbcn, with a= 10.686(2), b= 13.832(4), c= 16.129(4)Å, and Z= 4. The structure has been solved by the heavy-atom method and refined by full-matrix least squares to R 0.044 for 1 420 diffractometric intensity data. The crystals contain discrete molecules in which the platinum co-ordination is square planar. The Pt–Cl bond vector coincides with a crystallographic diad axis about which the atoms of the vinyl group are disordered. Selected bond lengths (Å) are Pt–Cl 2.398(4), Pt–P 2.295(3), and Pt–C 2.03(2). The Pt–CC angle is 127(2)°. From a survey of the available structural data it is concluded that there is little, if any, back donation from platinum to carbon in platinum–alkenyl linkages.

Sterically hindered metal alkenyls. Part 1. Synthesis, reactions, and crystal and molecular structures of some palladium and platinum σ-alkenyls

The compounds trans-[PtBr{C(C10H15)CH2}(PEt3)2](1)(C10H15= adamant-1-yl), trans-[MBr{C(C10H7)CMe2}(PEt3)2][M = Pd (2) or Pt (3); C10H7= naphth-1-yl], and trans-[MBr{C(Ph)CMe2}(PEt3)2][M = Pd (4) or Pt (5)] have been prepared from Grignard [for (2) and (3)] or lithium reagents [for (1), (4), and (5)] and appropriate dichlorobis(phosphine)metal derivatives. Full single-crystal X-ray data are reported for (1) and (3), and reveal unusually long Pt–C(sp2) bonds. Insertion reactions into these M–C bonds occur with MeNC [for (1), (3), and (5)], and with CO [for (1) and (3)]; the latter, the first reported insertion into a Pt–C(sp2) bond, occurs under mild conditions as expected for the abnormally long M–C bonds.

Complete sequence and molecular epidemiology of IncK epidemic plasmid encoding bla(CTX-M-14)

Antimicrobial drug resistance is a global challenge for the 21st century with the emergence of resistant bacterial strains worldwide. Transferable resistance to beta-lactam antimicrobial drugs, mediated by production of extended-spectrum beta-lactamases (ESBLs), is of particular concern. In 2004, an ESBL-carrying IncK plasmid (pCT) was isolated from cattle in the United Kingdom. The sequence was a 93,629-bp plasmid encoding a single antimicrobial drug resistance gene, bla(CTX-M-14). From this information, PCRs identifying novel features of pCT were designed and applied to isolates from several countries, showing that the plasmid has disseminated worldwide in bacteria from humans and animals. Complete DNA sequences can be used as a platform to develop rapid epidemiologic tools to identify and trace the spread of plasmids in clinically relevant pathogens, thus facilitating a better understanding of their distribution and ability to transfer between bacteria of humans and animals.

Local orientational disorder in peptide fibrils probed by a combination of residue-specific 13C-18O labelling, polarised infrared spectroscopy and molecular combing

A novel combination of site-specific isotope labelling, polarised infrared spectroscopy and molecular combing reveal local orientational ordering in the fibril-forming peptide YTIAALLSPYSGGRADS. Use of 13C-18O labelled alanine residues demonstrates that the Nterminal end of the peptide is incorporated into the cross-beta structure, while the C-terminal end shows orientational disorder

Synthesis, characterization and molecular structure of 1,1′ bis (diphenyl phosphino ferrocene) dioxide complex of the cis-uranyl dichloride

A 1,1' bis(diphenyl phosphino ferrocene) dioxide complex of the uranyl dichloride was synthesized and characterized by elemental analysis, H-1, P-31{H-1} NMR and X-ray diffraction methods. The structure of the compound shows that the uranium(VI) ion is surrounded by four oxygen and two chlorine atoms in an octahedral geometry. Two oxygen atoms from the bis (diphenyl phosphino ferrocene) dioxide and two chlorine atoms form a square planar arrangement. Two uranyl oxygen atoms occupy the axial positions. The bis(diphenyl phosphino ferrocene) dioxide ligand acts as a bidentate chelating ligand with a bite angle of 82.90(16)degrees around the uranyl group. The two chlorine atoms are mutually cis with a CI-U-Cl angle of 97.75(7)degrees.

What have dendritic cells ever done for adjuvant design? Cellular and molecular methods for the rational development of vaccine adjuvants

Our new molecular understanding of immune priming states that dendritic cell activation is absolutely pivotal for expansion and differentiation of naïve T lymphocytes, and it follows that understanding DC activation is essential to understand and design vaccine adjuvants. This chapter describes how dendritic cells can be used as a core tool to provide detailed quantitative and predictive immunomics information about how adjuvants function. The role of distinct antigen, costimulation, and differentiation signals from activated DC in priming is explained. Four categories of input signals which control DC activation – direct pathogen detection, sensing of injury or cell death, indirect activation via endogenous proinflammatory mediators, and feedback from activated T cells – are compared and contrasted. Practical methods for studying adjuvants using DC are summarised and the importance of DC subset choice, simulating T cell feedback, and use of knockout cells is highlighted. Finally, five case studies are examined that illustrate the benefit of DC activation analysis for understanding vaccine adjuvant function.