56 research outputs found
Complexation of Secondary Amides to Chromium(III): the X-Ray Structure of a Molecule with Two Modes of Monodentate Organic Amide Co-ordination
The X-ray crystal structure of the dimer [Cr{H(chba-Et)}(py)_2]_(2)·2py [H_(4)(chba-Et)= 1,2-bis(3,5-dichloro-2-hydroxybenzamido) ethane, py = pyridine] establishes, for the first time, the existence of N-co-ordination of an organic amide to Cr^III, the N-atom and carbonyl O-atom of two separate amide groups being co-ordinated to each Cr^III centre [Cr–N 2.030(6) and Cr–O 1.976(5)Å]; the potentially tetra-anionic chelating ligand leads to a variety of co-ordination modes
A new mechanism for exchange processes observed in the compounds [M(η-C_5H_5)_2(exo-η-RCH = CH_2)H], M = Nb and Ta
Dynamic n.m.r. studies of the exchange processes in the complexes [M(η-C_5H_5)(exo-η-RCH=CH_2)H], M = Nb, Ta, lead to the proposal of a new mechanism involving intermediates with agostic bonding
Rearrangement of bicyclo[2.2.1]heptane ring systems by titanocene alkylidene complexes to bicyclo[3.2.0]heptane enol ethers. Total synthesis of (±)-Δ^(9(12))-capnellene
A variety of ester-substituted norbornenes react with titanamethylene complex (Tebbe's reagent) to yield stable
titanacyclobutanes. Endo esters do not react with the reagent in competition with the norbornene double bond.
The X-ray structure of the metallacycle formed from titanacene methylene complex and 1-methylbicyclo[2.2.l]hept-5-ene-2,3-dicarboxylic acid diisopropyl ester was determined. On heating, the metallacycle rearranged
to a carbene-olefin complex. The ratio of productive opening, cleavage of the bicycloheptane ring system, to
nonproductive opening, regeneration of the starting materials, is controlled by a variety of steric factors that
were studied and analyzed. The productive opening was detected by the formation of the product resulting from
the intramolecular trapping of the intermediate titanium alkylidene by the endo ester functionality in a Wittig-like
reaction to yield substituted bicyclo[3.2.0]heptenes. Rearrangement of the titanacycle formed from 4,4-dimethyltricyclo[
5.2.1.0^(1,5)]dec-8-ene-6-carboxylic acid tert-butyl ester yielded 10,10-dimethyl-3-methoxy-7-
vinyltricyclo[5.3.0.0^(2,5)]dec-2-ene, which was transformed into Δ ^(9(12))-capnellene in good yield
Carbonylation of titanocene cyclobutenes. Synthesis and characterization of a titanocene-vinylketene complex
Rearrangement of bicyclo[2.2.1]heptane ring systems by titanocene alkylidene complexes to bicyclo[3.2.0]heptane enol ethers. Total synthesis of (.+-.)-.DELTA.9(12)-capnellene
Efforts to enhance coverage of crystallography in United States secondary education
Because crystallography has often been regarded as an ‘experts only’ science, requiring advanced mathematics and physics, it has been eliminated from many science curricula. In the United States, high school is a critical time when students are exposed to science at a more significant level, preparing them for university, and it is when they make career choices. A contemporary secondary science teaching credential must qualify teachers to present topics in substantive ways, to attract talented and enthusiastic young people to science, and to develop scientific literacy in the future workforce. Education and training policies put forward by the United States National Committee for Crystallography and the American Crystallographic Association recommend that molecular structure awareness should begin in K-12 (kindergarten through 12th grade) education as a core component for implementing established national science standards. Furthermore, many contexts exist in which crystallography can be incorporated into secondary education with minimal disruption. Following these guidelines, preparation of secondary teachers should include professional development in crystallography, providing them with knowledge (fundamental and practical), learning units, tools and modern examples to incorporate into their curricula. This article describes activities whose objective is to enhance secondary education by raising crystallography awareness through workshops, summer schools, student/teacher research internships and remoteenabling technologies
Structure of the Francisella tularensis enoyl-acyl carrier protein reductase (FabI) in complex with NAD+ and triclosan
Structure of the ternary complex of F. tularensis enoyl-acyl carrier protein reductase reveals the structure of the substrate binding loop whose electron density was missing in an earlier structure, and demonstrates a shift in the position of the NAD+ cofactor
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Reactions of osmium(IV) complexes of PAC ligands with azide species
Structure of dihydroorotase from Bacillus anthracis at 2.6 Å resolution
A comparison is made between the structures of dihydroorotase from four different organisms, including B. anthracis dihydroorotase, and reveals substantial variations in the active site, dimer interface and overall tertiary structure
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