121 research outputs found
Reactivity of tri(2-furyl)phosphine (Pfu\u3csub\u3e3\u3c/sub\u3e) with [Mn\u3csub\u3e2\u3c/sub\u3e(CO)\u3csub\u3e10–\u3cem\u3en\u3c/em\u3e\u3c/sub\u3e(NCMe)\u3csub\u3e\u3cem\u3en\u3c/em\u3e\u3c/sub\u3e] (\u3cem\u3en\u3c/em\u3e = 0–2): X-ray Structure of \u3cem\u3emer\u3c/em\u3e-[Mn(CO)\u3csub\u3e3\u3c/sub\u3e(η\u3csup\u3e1\u3c/sup\u3e-C\u3csub\u3e4\u3c/sub\u3eH\u3csub\u3e3\u3c/sub\u3eO)(Pfu\u3csub\u3e3\u3c/sub\u3e)\u3csub\u3e2\u3c/sub\u3e]
In the search for new examples of systems that self-assemble into cyclic metal–organic architectures, the six isomers of X,Y′-bis(di(1H-pyrazolyl)methane)-1,1′-biphenyl, LXY, and their silver(I) trifluoromethanesulfonate complexes were prepared. Five of the six silver complexes gave crystals suitable for single crystal X-ray diffraction, with only the microcrystalline derivative of 2,3′-bis(di(1H-pyrazolyl)methane)-1,1′-biphenyl, L23, proving to be unsuitable for this analysis. Of the structurally characterized silver(I) complexes, that with L22 showed an unusual trans-spanning chelating coordination mode to silver. At the same time the ligand was also bound to a second silver center giving rise to a cyclic supramolecular isomer with a 22-membered metallacycle. The complex of L34 also gave a cyclic dication but with a remarkable 28-membered metallacycle ring. The remaining three derivatives were polymeric. The results of this study underscore that a 120° angle between dipyrazolylmethyl moieties across aromatic spacers will give rise to a cyclic dication but this is not an exclusive requirement for the formation of cyclic architectures. Also, the supramolecular structures of complexes are assembled via a variety of noncovalent interactions involving the di(pyrazolyl)methyl cation most notably by weak hydrogen bonding interactions involving the methine hydrogen and an oxygen atom of the triflate anion
Cleavage of Ge–S and C–H bonds in the reaction of electron-deficient [Os₃(CO)₈(μ-H)(μ₃-Ph₂PCH₂P(Ph)C₆H₄)] with Ph₃GeSPh: Generation of thiophenol derivatives [Os₃(CO)₈(μ-H)(μ-SPh)(μ-dppm)] and [Os₃(CO)₇(μ-H)(μ-SPh)(μ₃-SC₆H₄)(μ-dppm)]
Heating the electron-deficient [Os₃(CO)₈(μ-H)(μ₃-Ph₂PCH₂P(Ph)C₆H₄)] (1) and Ph₃GeSPh in benzene at 80 °C led to the thiolato bridged compounds, [Os₃(CO)₈(μ-H)(μ-SPh)(μ-dppm)] (2) and [Os₃(CO)₇(μ-H)(μ-SPh)(μ₃-SC₆H₄)(μ-dppm)] (3), formed by cleavage of Ge–S and C–S bonds of the ligand, in 40% and 17% yields, respectively. Both compounds 2 and 3 have been characterized by a combination of elemental analysis, infrared and ¹H NMR spectroscopic data together with single crystal X-ray crystallography. Compound 3 contains an open triangle of osmium atoms bridged by a SPh and SC₆H₄ ligands on opposite sides of the cluster with a dppm ligand bridging one of the Os–Os edges. Compound 2 consists of a closed triangular cluster of osmium atoms with a bridging SPh, and a bridging hydride ligand on the same Os–Os edge, and a dppm ligand bridging one of the remaining Os–Os edges
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
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
Activation of Tri(2-Furyl)Phosphine at a Dirhenium Centre: Formation of Phosphido-Bridged Dirhenium Complexes
Reaction of tri(2-furyl)phosphine (PFu3) with [Re2(CO)10−n(NCMe)n] (n = 1, 2) at 40 °C gave the substituted complexes [Re2(CO)10−n(PFu3)n] (1 and 2), the phosphines occupying axial position in all cases. Heating [Re2(CO)10] and PFu3 in refluxing xylene also gives 1 and 2 together with four phosphido-bridged complexes; [Re2(CO)8−n(PFu3)n(μ-PFu2)(μ-H)] (n = 0, 1, 2) (3–5) and [Re2(CO)6(PFu3)2(μ-PFu2)(μ-Cl)] (6) resulting from phosphorus–carbon bond cleavage. A series of separate thermolysis experiments has allowed a detailed reaction pathway to be unambiguously established. A similar reaction between [Re2(CO)10] and PFu3 in refluxing chlorobenzene furnishes four complexes which include 1, 2, 6 and the new binuclear complex [Re2(CO)6(η1-C4H3O)2(μ-PFu2)2] (7). All new complexes have been characterized by a combination of spectroscopic data and single crystal X-ray diffraction studies
Hydrogenase biomimetics:structural and spectroscopic studies on diphosphine-substituted derivatives of Fe2(CO)6(µ-edt) (edt = ethanedithiolate) and Fe2(CO)6(µ-tdt) (tdt = 1,3-toluenedithiolate)
Hydrogenase biomimics containing redox-active ligands: Fe2(CO)4(μ-edt)(κ2-bpcd) with electron-acceptor 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) as a potential [Fe4–S4]H surrogate
Fluorinated models of the iron-only hydrogenase: An electrochemical study of the influence of an electron-withdrawing bridge on the proton reduction overpotential and catalyst stability
AbstractHere we report the synthesis, electrochemistry and electrocatalytic activity of Fe2(CO)6(μ-SC6F5)2 (1) where the highly fluorinated bridge is electron-withdrawing, resulting in decreased electron-density at the iron–iron bond. Additionally we discuss the related substituted complexes Fe2(CO)5(PPh3)(μ-SC6F5)2 (2) and Fe2(CO)4(μ-Ph2PCH2PPh2)(μ-SC6F5)2 (3). As none of the complexes could be protonated in their neutral form it was found that proton reduction catalysis in the presence of strong acid (HBF4) took place at the potential of the first reduction of complex 1 and 3, following an EC mechanism. Complex 2 was unstable in the presence of strong acid. For 1 the potential at which proton reduction took place represented a relatively mild reduction potential (−1.15V vs. Fc/Fc+ in acetonitrile) that was comparable to examples of similar complexes in the literature. Complex 1 generated a small concentration of a highly catalytic species after electrochemical reduction, which we attribute to cleavage of the Fe–Fe bond and formation of a mono-nuclear iron species or to Fe–S bond breakage generating a vacant coordination site. The contributions to the catalytic currents were simulated using DigiSim, where it was found that the rate limiting step for 3 was the elimination of H2. It was also found that the highly catalytic species generated after reduction of 1 was more basic than 1− and also that protonation of this species was faster
High Rectification Ratio at Room Temperature in Rhenium(I) Compound
Electrical current rectification is an interesting electronic feature,
popularly known as a diode. Achieving a high rectification ratio in a molecular
junction has been a long-standing goal in molecular electronics. The present
work describes mimicking electrical current rectification with pi-stacked
rhenium(I) compound sandwiched between two electrical contacts. Among the two
mononuclear rhenium compounds studied here, [Re(CO)4(PPh3){(N)-saccharinate}]
(1) and [Re(CO)3(phen){(N)-saccharinate}] (2), the latter show strong pi-pi
interactions-induced high rectification ratio of ~ 4000 at 2.0 V at room
temperature. Alternating current (AC)-based electrical measurements ensuring AC
to DC electrical signal conversion at a frequency f of 1 KHz showing 2 can act
as an excellent half-wave rectifier. Asymmetric charge injection barrier height
at the electrode/Re(I) interfaces of the devices with a stacking configuration
of p++-Si/Re compound31nm(2)/ITO originates the flow of electrical current
unidirectionally. The charge transport mechanism governed by thermally
activated hopping phenomena, and charge carrier propagation is explained
through an energy profile considering the Fermi levels of two electrodes, and
the energy of frontier molecular orbitals, HOMO, and LUMO, confirming
rectification is of a molecular origin. The present work paves the way to
combine different organometallic compounds as circuit elements in
nanoelectronic devices to achieve numerous exciting electronic features.Comment: 16 pages, 5 figure
Particle-hopping Models of Vehicular Traffic: Distributions of Distance Headways and Distance Between Jams
We calculate the distribution of the distance headways (i.e., the
instantaneous gap between successive vehicles) as well as the distribution of
instantaneous distance between successive jams in the Nagel-Schreckenberg (NS)
model of vehicular traffic. When the maximum allowed speed, , of the
vehicles is larger than unity, over an intermediate range of densities of
vehicles, our Monte Carlo (MC) data for the distance headway distribution
exhibit two peaks, which indicate the coexistence of "free-flowing" traffic and
traffic jams. Our analytical arguments clearly rule out the possibility of
occurrence of more than one peak in the distribution of distance headways in
the NS model when as well as in the asymmetric simple exclusion
process. Modifying and extending an earlier analytical approach for the NS
model with , and introducing a novel transfer matrix technique, we
also calculate the exact analytical expression for the distribution of distance
between the jams in this model; the corresponding distributions for have been computed numerically through MC simulation.Comment: To appear in Physica
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