Addition Of Thiocyanate Ion Research Articles

Testing diverse strategies for ruthenium catalyst removal after aqueous homogeneous olefin metathesis

Traditionally, olefin metathesis (OM) is carried out in organic solvents such as dichloromethane or toluene. Due to the development of water-resistant or even water-soluble ruthenium catalysts in the last two decades, considerable progress on OM in aqueous media has been made. However, the removal of ruthenium from the product of OM reactions performed in water remains a substantial challenge. In the present work, selected approaches to purify the reaction mixtures after aqueous homogeneous olefin metathesis (AHOM) reactions have been probed to address this shortcoming. It was found that elimination of a water-soluble Ru catalyst after AHOM conducted in neat water can be achieved via addition of thiocyanate ions (with or without support of charcoal additive). The developed purification method can make the aqueous metathesis methodology more practical, allowing easier separation of a spent water-soluble catalyst from the water-soluble metathesis products. Unfortunately, this methodology did not provide satisfactory results in the case of AHOM reactions performed in water/alcohol mixtures. To allow separation of a Ru catalyst in the latter case, a method utilizing a stimuli-responsive polymer was tested, leading however to limited success.

Effect of SCN¯ and NO3¯ ions on the extraction of heavy metals from aqueous solutions with the ionic liquid trihexylammonium octanoate

The protic ionic liquid, trihexylammonium octanoate [T6AC7COO], was used in order to extract heavy metals ions, such as Cu(II), Co(II) and Ni(II), from aqueous solutions at room temperature, using different counter anions (SO42−, Cl− and NO3−). This ionic liquid is highly selective towards copper(II) but not to cobalt(II) and nickel(II). The metal ion extraction capacity of [T6AC7COO] also depends on the counter anion of the metal salt: NO3−> Cl−> SO42−. When nitrate ions (NO3¯) are added to aqueous solutions containing CoSO4, CoCl2, NiSO4, or NiCl2, before the extraction process, the extraction efficiency of [T6AC7COO] is increased from near zero percent to around 20%−40%, which can be considered as a good rise. However, the addition of thiocyanate ions (SCN−) to aqueous solutions, instead of nitrate ions, increases substantially the Co(II) and Ni(II) recovery yields. Practically all the metal ions together with SCN− ions are transferred from the aqueous phase to the ionic liquid phase. In the extracted phase, SCN−anions bind to the metal center through the N atoms. In contrast, the other anions do not coordinate with the metal ion. For all extraction processes, an ion-par extraction is the dominant mechanism. 1H NMR, FT-IR and ion chromatography were used in order to confirm the extraction mechanism, and UV–visible spectroscopy and ICP-OES were used to estimate the extraction efficiency of [T6AC7COO].

2-Phenyl-2-(2-pyridyl)imidazolidine (PPI) as New Catalyst in the Efficient, Mild, and Regioselective Conversion of Epoxides to Thiocyanohydrines with Ammonium Thiocyanate

2-Phenyl-2-(2-pyridyl)imidazolidine (PPI) catalysis the addition of thiocyanate ion to epoxides to afford g -hydroxy thiocyanate in high yields, mild conditions, and regioselectivity. Thus, several 2-hydroxyethyl thiocyanates, which are useful intermediates toward biological active molecules, are obtained easily in very good yields.

Competing base-promoted E2 and E1 reactions of an acidic tertiary substrateElectronic supplementary information (ESI) available: the effect of base concentration on rate constant and product composition. See http://www.rsc.org/suppdata/p2/b2/b200758d/

The solvolysis of 4-chloro-4-(4′-nitrophenyl)pentan-2-one (1-Cl) in aqueous acetonitrile yields the alcohol 4-hydroxy-4-(4′-nitrophenyl)pentan-2-one (1-OH) and the elimination products 4-(4′-nitrophenyl)-2-oxopent-4-ene (2), (E)-4-(4′-nitrophenyl)-2-oxopent-3-ene (3), and (Z)-4-(4′-nitrophenyl)-2-oxopent-3-ene (4). Addition of thiocyanate ion does not increase the total reaction rate in 25 vol% acetonitrile in water, but gives rise to the substitution products 1-SCN and 1-NCS, at the expense of 1-OH, and a small increase in the fraction of alkene 3. Addition of acetate ion and other weak bases gives rise to base-promoted E2 (or E1cB) to give alkene 3 (and 4). The Bronsted parameter for this reaction was measured as β = 0.76. Water-promoted E2 (or E1cB) reaction was not observed.

Crystal structure of an antiferromagnetically coupled µ-carbonato-bridged dinickel(II) complex containing the pendent-arm macrocycl 1-(3-dimethylaminopropyl)-1,5,9-triazacyclododecane (L1); a system which readily sequesters carbon dioxide from air

The nickel(II) complex of the pendent-arm macrocycle 1-(3-dimethylaminopropyl)-1,5,9-triazacyclododecane (L1) sequesters CO2 from air to yield, after addition of thiocyanate ion, [{(HL1)Ni(NCS)}2(CO3)]2+, the first example of a µ-carbonato dinickel(II) complex; the Ni atoms are antiferromagnetically coupled with the exceptionally large exchange constant –2J= 94.6 ± 0.4 cm–1.

Processes of the activation of passive iron by thiocyanate ion

The activation of passive iron has been examined in neutral or weak alkaline solutions containing thiocyanate ions. The passivation of iron was carried out potentiodynamically, and the specimen potential was allowed to decay under open-circuit conditions. The residual passive film was then subjected to the cathodic reduction in order to estimate its thickness. The spontaneous potential decay was very much influenced by the addition of thiocyanate ions. The duration of the potential arrest was shortened with increasing concentration of thiocyanate ions. The potential-determining reaction and the role of the thiocyanate ion are discussed.

Processes of the activation of passive iron by thiocyanate ion

The activation of passive iron has been examined in neutral or weak alkaline solutions containing thiocyanate ions. The passivation of iron was carried out potentiodynamically, and the specimen potential was allowed to decay under open-circuit conditions. The residual passive film was then subjected to the cathodic reduction in order to estimate its thickness. The spontaneous potential decay was very much influenced by the addition of thiocyanate ions. The duration of the potential arrest was shortened with increasing concentration of thiocyanate ions. The potential-determining reaction and the role of the thiocyanate ion are discussed.