Cleavage Of Se Research Articles

Seeded Chemical Vapor Transport Growth of Cu2OSeO3

We present an optimized seeded chemical vapor transport method for the growth of Cu2OSeO3 that allows for chemical control in a system with many stable phases to selectively produce large phase-pure single crystals. This method is shown to consistently produce single crystals in the range of 120 to 180 mg. A Wulff construction model of a representative crystal shows that the minimum energy surface is {1 1 0}, followed by {1 0 0}. Analysis of the lowest index planes revealed that cleavage of Se–O bonds has a large energy cost, leading to an overall high surface energy. The seeded chemical vapor transport demonstrated here shows promise for large single crystal growth of other functional materials such as Weyl semimetals, frustrated magnets, and superconductors.

KI catalyzed azidoselenenylation of alkenes with sodium azide and diselenides via an oxidative cleavage of Se–Se bond

GRAPHICAL ABSTRACT

Iron-Mediated Cleavage of Se—Se Bond for the Synthesis ofα-Arylseleno Carbonyl Compounds

In the presence of iron dust, using commercial N,N-dimethylformamide (DMF) as solvent, diaryl diselenides re- acted with α-bromo carbonyl compounds at 90 ℃ under nitrogen atmosphere to afford a series of α-arylseleno carbonyl compounds. The influence of temperature, reaction time, solvent and iron dosage on the reaction was investigated. The results showed that the influence of temperature on the reaction was most obvious. In addition, the influence of carbonyl substituent in α-bromo carbonyl compounds was also more obvious. When carbonyl substituent is phenyl, the yield was lower than that of methyl or alkoxy. A proposal mechanism is that iron dust reacted with diaryl diselenides to give the nucleophilic species ArSeFeSeAr, and nucleophilic species ArSeFeSeAr and electrophilic α-bromo carbonyl compounds occured nucleophilic substitution reaction to obtain the desire products. The method using the iron dust to promote the cleavage of Se—Se bond has advantages of safe non-toxic, cheap and easy to get raw materials, simple procedure. Keywords iron dust; cleavage of Se—Se bond; diaryl diselenides; α-bromo carbonyl compounds; α-arylseleno carbonyl compounds

Electron Capture Dissociation of Disulfide, Sulfur–Selenium, and Diselenide Bound Peptides

To examine the electron capture dissociation (ECD) behavior of disulfide (S-S), sulfur-selenium (S-Se), and diselenide (Se-Se) bonds-containing peptides, a series of free cysteine (Cys) and selenocysteine (Sec) containing peptides were reacted to form interchain S-S, S-Se, and Se-Se bonds, and then studied using ECD with Fourier transform ion cyclotron mass spectrometry (FTICR MS). These results demonstrate that the radical has higher tendency to stay at selenium rather than sulfur after the cleavage of Se-S bonds by ECD. In addition, -SH (-33), -S (-32), and -S + H (-31) small neutral losses were all observed from the cleavage of C-S bonds of a disulfide bound peptide. Similar, but minor, fragments were also detected in S-Se bound peptides. In contrast, the cleavage of C-Se bonds of the Se-Se species mainly forms fragments with neutral loss of -Se + H (-78.90868), and the radical tends to stay on the selenium of its corresponding complementary pair. Although the electron affinities of S atom (2.07 eV) and Se atom (2.02 eV) are very close; they have very different reactivity towards electrons. The replacement of sulfur with selenium greatly increases the electron affinities of S-Se and Se-Se bonds comparing to S-S bonds (with an increase of electron affinity by about 0.20 eV by replacing a sulfur with a selenium) (Int J Quantum Chem 110:513-523, 2010), which in turn leads to different ECD fragmentation behavior and mechanisms. Our results are in good agreement with previously published ab initio calculations on Se-Se compounds by other groups.

Regioselective ring-opening of aziridines with diselenides and disulfides using the Zn/AlCl3 system

An efficient Zn/AlCl3-promoted highly regioselective one-pot procedure has been demonstrated for the synthesis of β -amino selenides and sulfides from a variety of diselenides/disulfides and aziridines by reductive cleavage of Se–Se and S–S bonds using the Zn/AlCl3 system in acetonitrile under very mild conditions.

Synthesis, characterization and coordination properties of bis(alkyl)selenosalen ligands

New bis (alkyl) selenosalen podand ligands having Se2N2 donor sites have been synthesized by the condensation of unsymmetrical o-formylphenyl alkyl selenide (1-3) with ethylenediamine. The reaction of bis(alkyl)selenosalen podands with Pd(II) and Pt(II) afforded selenoether-selenolate coordination complexes 7-10via cleavage of one of the two Se-C(alkyl) bonds of bis(alkyl)selenosalen podands upon complexation. DFT calculations revealed that the cleavage of Se-C(alkyl) bonds occurred possibly via S(N)2 mechanism instead of a sequence of oxidative addition and reductive elimination reactions. The spectral data and elemental analyses confirmed the formation of selenoether-selenolate complexes. The structures of the podands N,N'-bis[(2-methylseleno)phenylmethylene]-1,2-ethanediamine (4), N,N'-bis[(2-decylseleno)phenylmethylene]-1,2-ethanediamine (5) and the selenoether-selenolate complex 8 have been determined by single crystal X-ray diffraction analysis. The crystal structure of 5 showed SeH interaction with a ladder like 3D supramolecular arrangement via interdigitation of long alkyl chains. Comparison of crystal packing of podands 4 and 5 indicates that the alkyl chain length has significant impact on the crystal packing. The platinum selenolate complex 8 shows a square planar arrangement around the Pt centre, where the Se atoms in the selenolate and the selenoether have nearly equal Pt-Se bond length.

Synthesis of Unsymmetrical Pyridyl Aryl Selenides by the Reductive Cleavage of Se─Se Bond

An efficient protocol for the synthesis of novel hitherto unknown substituted and unsubstituted phenyl pyridyl selenides from dipyridyl/diphenyl diselenides and phenyl/pyridyl halides in the presence of copper catalysed system, Cu 2 O/Mg/bpy is being presented. All the synthesized selenides are either light yellow coloured liquids or low melting solids. All the newly synthesized compounds have been thoroughly characterized by elemental analysis employing various spectroscopic techniques viz., infrared, multinuclear NMR ( 1 H, 13 C, 77 Se) and mass spectrometry (in representative cases).

A Novel Synthesis of Unsymmetrical Selenides via the Cleavage of Se–se Bond by Sm/cat.CoCl2 System

Promoted by Sm/cat. CoCl2 system, the Se–Se bond of diaryldiselenides was easily cleaved to form a “living” intermediate, which reacted readily with alkyl halides to afford unsymmetrical alkylarylselenides in good yields under mild and neutral reaction conditions.

Newer Aspects in Synthetic Methodology of Pyridyl Chalcogen (E═Se/Te) Compounds

A number of synthetic protocols for the synthesis of symmetrical dipyridyl chalcogenides/dichalcogenides have successfully been developed by employing cheap, economically viable and eco-friendly reagents. The reductive cleavage of Se–Se and Te–Te bond in these versatile compounds conveniently have been achieved and a number of hitherto unknown chelating seleno/telluro ethers with varying back bones have been prepared employing appropriate alkylating agents.

Reductive Cleavage of Se–Si Bond in Arylselenotrimethylsilane: A Novel Method for the Synthesis of Selenoesters

Arylselenotrimethylsilane is reduced by samarium diiodide to yield samarium arylselenolates. These new selenolate anion species reacted smoothly with acyl halides to give selenoesters.

Photochemical reactions between tertiary phosphines and organic diselenides

Tertiary phosphines, PR13, react with organic diselenides, Se2R22, under u.v. radiation to produce PR13Se and SeR22. The reaction rates decrease in the orders R13, = Me2Ph > MePh2 > Ph3 and R2= CH2Ph > Et > Me > Ph. A radical-chain mechanism appears to operate via SeR2˙ and PR13(SeR2)˙. Although cleavage of Se–C bonds may be involved in the u.v. irradiation of Se2R22, cleavage of Se–Se bonds seems more important in these reactions, even for R2= CH2Ph.