1,243 research outputs found
Reactivity of acyclic (pentadienyl)iron(1+) cations: Synthetic studies directed toward the frondosins
A short, 4-step route to the scaffold of frondosin A and B is reported. The [1-methoxycarbonyl-5-(2′,5′-dimethoxyphenyl)pentadienyl]Fe(CO)3+ cation was prepared in two steps from (methyl 6-oxo-2,4-hexadienoate)Fe(CO)3. Reaction of this cation with isopropenyl Grignard or cyclohexenyllithium reagents affords (2-alkenyl-5-aryl-1-methoxycarbonyl-3-pentene-1,5-diyl)Fe(CO)3 along with other addition products. Oxidative decomplexation of these (pentenediyl)iron complexes, utilizing CuCl2, affords 6-aryl-3-methoxycarbonyl-1,4-cycloheptadienes via the presumed intermediacy of a cis-divinylcyclopropane
The Crystal and Molecular Structure of a Trifluoroacetylacetonate Complex of Scandium, Sc(CH\u3csub\u3e3\u3c/sub\u3eCOCHCOCF\u3csub\u3e3\u3c/sub\u3e)\u3csub\u3e3\u3c/sub\u3e
The crystal and molecular structure of Sc(CH3COCHCOCF3)3 has been determined by X-ray diffraction. The compound crystallizes as pure mer-isomer in the orthorhombic space group Pbca with lattice parameters a=15.166(8) Å, b=13.560(7) Å, c=19.327(10) Å, α=β=γ=90°, V=3974(4) Å3, Z=8. The complex at 100 K is partially disordered in the crystal structure in an approximate 5:1 ratio with 83% fluorine population at C-11 and 17% at C-15. NMR data is compared to that previously reported
Multiple memory formation in glassy landscapes
Cyclically sheared jammed packings form memories of the shear amplitude at
which they were trained by falling into periodic orbits where each particle
returns to the identical position in subsequent cycles. While simple models
that treat clusters of rearranging particles as isolated two-state systems
offer insight into this memory formation, they fail to account for the long
training times and multi-period orbits observed in simulated sheared packings.
We show that adding interactions between rearranging clusters overcomes these
deficiencies. In addition, interactions allow simultaneous encoding of multiple
memories which would not have been possible otherwise. These memories are
different in an essential way from those found in other systems, such as
multiple transient memories observed in sheared suspensions, and contain
information about the strength of the interactions.Comment: 7 pages, 6 figure
State-and-rate friction in contact-line dynamics
In order to probe the dynamics of contact-line motion, we study the
macroscopic properties of sessile drops deposited on and then aspirated from
carefully prepared horizontal surfaces. By measuring the contact angle and drop
width simultaneously during droplet removal, we determine the changes in the
shape of the drop as it depins and recedes. Our data indicate that there is a
force which opposes the motion of the contact line that depends both on the
amount of time that the drop has been in contact with the surface and on the
withdrawal rate. For water on silanized glass, we capture the experimentally
observed behavior with an overdamped dynamical model of contact-line motion in
which the phenomenological drag coefficient and the assumed equilibrium contact
angle are the only inputs. For other liquid/substrate pairs, the observed
contact-line motion suggests that a maximum static friction force is important
in addition to damping. The dependence on time of contact and withdrawal rate,
reminiscent of rate-and-state friction between solid surfaces, is qualitatively
consistent across three substrate-liquid pairs.Comment: 10 pages, 10 figure
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Multiple memory formation in glassy landscapes
Cyclically sheared jammed packings form memories of the shear amplitude at which they were trained by falling into periodic orbits where each particle returns to the identical position in subsequent cycles. While simple models that treat clusters of rearranging particles as isolated two-state systems offer insight into this memory formation, they fail to account for the long training times and multiperiod orbits observed in simulated sheared packings. We show that adding interactions between rearranging clusters overcomes these deficiencies. In addition, interactions allow simultaneous encoding of multiple memories, which would not have been possible otherwise. These memories are different in an essential way from those found in other systems, such as multiple transient memories observed in sheared suspensions, and contain information about the strength of the interactions
P–C and C–H Bond Cleavages of dppm in the Thermal Reaction of [Ru\u3csub\u3e3\u3c/sub\u3e(CO)\u3csub\u3e10\u3c/sub\u3e(μ-dppm)] with Benzothiophene: X-ray structures of [Ru\u3csub\u3e6\u3c/sub\u3e(μ-CO)(CO)\u3csub\u3e13\u3c/sub\u3e{μ\u3csub\u3e4\u3c/sub\u3e-PhP(C\u3csub\u3e6\u3c/sub\u3eH\u3csub\u3e4\u3c/sub\u3e)PPh}(μ\u3csub\u3e6\u3c/sub\u3e-C)] and [Ru\u3csub\u3e4\u3c/sub\u3e(CO)\u3csub\u3e9\u3c/sub\u3e(μ\u3csub\u3e3\u3c/sub\u3e-η\u3csup\u3e2\u3c/sup\u3e-PhPCH\u3csub\u3e2\u3c/sub\u3ePPh\u3csub\u3e2\u3c/sub\u3e)(μ\u3csub\u3e4\u3c/sub\u3e-η\u3csup\u3e6\u3c/sup\u3e:η\u3csup\u3e1\u3c/sup\u3e:η\u3csup\u3e1\u3c/sup\u3e-C\u3csub\u3e6\u3c/sub\u3eH\u3csub\u3e4\u3c/sub\u3e)(μ-H)]
The thermal reaction of [Ru3(CO)10(μ-dppm)] (1) with benzothiophene in refluxing toluene gives a complex mixture of products. These include the known compounds [Ru2(CO)6{μ-CH2PPh(C6H4)PPh}] (2), [Ru2(CO)6{μ-C6H4PPh(CH2)PPh}] (3), [Ru3(CO)9{μ3-η3-(Ph)PCH2P(Ph)C6H4}] (4) and [Ru3(CO)10{μ-η2-PPh(CH2)(C6H4)PPh}] (6), as well as the new clusters [Ru6(μ-CO)(CO)13{μ3-η2-PhP(C6H4)PPh}(μ6-C)] (5) and [Ru4(CO)9(μ3-η2-PhPCH2PPh2)(μ4-η6:η1:η1-C6H4)(μ-H)] (7). The solid-state molecular structures of 5 and 7 were confirmed by single crystal X-ray analyses. Compound 5 consists of interesting example of a hexaruthenium interstitial carbido cluster having a tetradentate diphosphine ligand derived from the activation of P–C and C–H bonds of the dppm ligand in 1. The tetranuclear compound 7 consists of a unique example of a non-planar spiked triangular metal fragment of ruthenium [Ru(1), Ru(2) and Ru(3)] unit with Ru(4) being bonded to Ru(1). The μ4-η1:η6:η1-benzyne ligand in this compound represents a previously uncharacterized bonding mode for benzyne. Compounds 5 and 7 do not contain any benzothiophene-derived ligand. The reaction of 4 with benzothiophene gives 2, 3, 5 and 6. Thermolysis of 1 in refluxing toluene gives 2, 3 and 4; none of 5 and 7 is detected in reaction mixture
Decarbonylation Reaction of [Os\u3csub\u3e3\u3c/sub\u3e(CO)\u3csub\u3e10\u3c/sub\u3e(\u3cem\u3eμ\u3c/em\u3e-H)(\u3cem\u3eμ\u3c/em\u3e-SN\u3csub\u3e2\u3c/sub\u3eC\u3csub\u3e4\u3c/sub\u3eH\u3csub\u3e5\u3c/sub\u3e)]: X-ray Structures of the Two Isomers of [Os\u3csub\u3e3\u3c/sub\u3e(CO)\u3csub\u3e9\u3c/sub\u3e(\u3cem\u3eμ\u3c/em\u3e-H)(\u3cem\u3eμ\u3c/em\u3e\u3csub\u3e3\u3c/sub\u3e-\u3cem\u3eη\u3c/em\u3e\u3csup\u3e2\u3c/sup\u3e-SN\u3csub\u3e2\u3c/sub\u3eC\u3csub\u3e4\u3c/sub\u3eH\u3csub\u3e5\u3c/sub\u3e)]
The thermal reaction of [Os3(CO)10(μ-H)(μ-SN2C4H5)] (1) at 110 °C afforded the new compound [Os3(CO)9(μ-H)(μ 3-η 2-SN2C4H5)] (2) in 84% yield. Compound 2 exists as two isomers, which differ in the disposition of the bridging hydride ligand. Both of the isomers of 2 have been characterized by a combination of elemental analysis, infrared and 1H NMR spectroscopic data together with single crystal X-ray crystallography. The isomers crystallize together in the triclinic space group P-1 with a = 10.4775(2), b = 13.3056(3), c = 15.0325(3) Å, α = 110.8890(10), β = 99.3880(10), γ = 96.1620(10)°, Z = 2 and V = 1900.31(7) Å3
Integrating fish fauna and habitat assessments: a fundamental step in developing Fishery Reserve Design Criteria
Isolating the enhanced memory of a glassy system
Studies of glassy systems have shown how cyclic driving forms memories of
amplitude. We explore how choice of driving protocol reveals dramatically
different features of this memory. We model rearranging soft spots in sheared
amorphous solids as hysterons. Cyclic shear with positive and negative shear
strain reveals a return-point memory of multiple strains known from experiments
and molecular dynamics simulations, while asymmetric driving (e.g. only
positive shear strains) suppresses multiple memories. However, when we
introduce frustrated interactions between hysterons, we identify a different
mechanism that restores multiple memories for asymmetric driving and can be
used for design. Our work suggests that this enhanced memory is a signature of
frustration.Comment: 5 pages, 5 figure
Investigations of 2-Thiazoline-2-thiol as a Ligand: Synthesis and X-ray Structures of [Mn\u3csub\u3e2\u3c/sub\u3e(CO)\u3csub\u3e7\u3c/sub\u3e(\u3cem\u3eμ\u3c/em\u3e-NS\u3csub\u3e2\u3c/sub\u3eC\u3csub\u3e3\u3c/sub\u3eH\u3csub\u3e4\u3c/sub\u3e)\u3csub\u3e2\u3c/sub\u3e] and [Mn(CO)\u3csub\u3e3\u3c/sub\u3e(PPh\u3csub\u3e3\u3c/sub\u3e)(\u3cem\u3eκ\u3c/em\u3e\u3csup\u3e2\u3c/sup\u3e-NS\u3csub\u3e2\u3c/sub\u3eC\u3csub\u3e3\u3c/sub\u3eH\u3csub\u3e4\u3c/sub\u3e)]
Treatment of Mn2(CO)10 with 2-thiazoline-2-thiol in the presence of Me3NO at room temperature afforded the dimanganese complexes [Mn2(CO)7(μ-NS2C3H4)2] (1) and [Mn2(CO)6(μ-NS2C3H4)2] (2) in 51 and 34% yields, respectively. Compound 1 was quantitatively converted into 2 when reacted with one equiv of Me3NO. Reaction of 1 with triphenylphosphine at room temperature furnished the mononuclear complex [Mn(CO)3(PPh3)(κ 2-NS2C3H4)] (3) in 66% yield. All three new complexes have been characterized by elemental analyzes and spectroscopic data together with single crystal X-ray diffraction studies for 1 and 3. Compound 1 crystallizes in the orthorhombic space group Pbca with a = 12.4147(2), b = 16.2416(3), c = 19.0841(4) Å, β = 90°, Z = 8 and V = 3848.01(12) Å3 and 3 crystallizes in the monoclinic space group P 21/n with a = 10.41730(10), b = 14.7710(2), c = 14.9209(2) Å, β = 91.1760(10)°, Z = 4 and V = 2295.45(5) Å3
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