A catalytic system based on complexes comprising abundant and cheap manganese together with readily available aminotriazole ligands is reported. The new Mn(I) complexes are catalytically competent in ...transfer hydrogenation of ketones with 2‐propanol as hydrogen source. The reaction proceeds under mild conditions at 80 °C for 20 h with 3 % of catalyst loading using either KOtBu or NaOH as base. Good to excellent yields were obtained for a wide substrate scope with broad functional group tolerance. The obtained results by varying the substitution pattern of the ligand are consistent with an out‐sphere mechanism for the H‐transfer.
Manganese transfer: Aminotriazole structures are readily accessible ligands for the synthesis of Mn(I) complexes. Three new ligands and four new Mn(I) complexes were prepared allowing to deduce favorable structural features for their use as catalysts in transfer hydrogenation of ketones. The catalyst shown is capable of reducing a broad scope of substrates with high functional group tolerance in high yields under mild conditions using either KOtBu or NaOH as base co‐catalysts.
A series of first row metal complexes (Co, Ni and Cu) containing commercial nitrogen ligands were synthetized and used as catalyst in the cycloaddition of CO
2
to epoxides. The reaction was carried ...out in ionic liquids based on 1-
n
-butyl-3-methylimidazolium as solvents. Best catalytic results were achieved with Co catalysts in 1-
n
-butyl-3-methylimidazolium tetrafluoroborate (BMIm.BF
4
). Under optimized reaction conditions cyclic carbonates were selectively obtained with good to excellent yields, presenting a reliable alternative to synthetize the product using low cost and abundant catalytic system containing a common ligand as ethylenediamine. Finally, macrocycle effects where studied in each case comparing the conversion rates obtained by using ethylenediamine and 1,4,8,11-tetraazacyclotetradecane.
Graphical Abstract
Manganese(
i
) complexes bearing triazole ligands are reported as catalysts for the hydrosilylation of carbonyl and carboxyl compounds. The desired reaction proceeds readily at 80 °C within 3 hours ...at catalyst loadings as low as 0.25 to 1 mol%. Hence, good to excellent yields of alcohols could be obtained for a wide range of substrates including ketones, esters, and carboxylic acids illustrating the versatility of the metal/ligand combination.
Manganese(
i
) complexes bearing readily accessible triazole ligands are effective catalysts for the hydrosilylation of carbonyl and carboxyl compounds.
Very simple and economical SiO 2 supported ionic liquid phase (SILP) materials are efficient catalysts for the addition of CO 2 to epoxides, producing cyclic carbonates in high yields (up to 99%) and ...selectivities (up to 99%). A range of ionic liquid (IL) concentrations (5–100 wt%), SiO 2 -supported 1- n -butyl-3-methylimidazolium halides (SBMIm·X: X = Cl, Br and I) ( 1–7 ) and 1-ethyl-3-(3-(trimethoxysilyl)propyl)-imidazolium halides (SEPIm·X) ( 8 , 9 ), were prepared and fully characterised. These hybrid materials are very active catalysts under mild reaction conditions (low temperature and atmospheric pressure or adsorbed CO 2 ). Under the optimal reaction conditions (S = 3.34 mmol, cat/S = 0.50, P CO2 = 5 bar, T = 80 °C), the best SILP system yields maximum conversion in just 30 min and can be reused at least five times without a noticeable decrease in activity and selectivity. The catalytic system is also active when using a CO 2 gas mixture from an industrial exhaust in both batch and continuous flow systems. A detailed structural and electronic analysis indicates that increasing the IL and water concentrations induces a solvation effect through the contact ion pair of the IL that drives the anions (Cl, Br and I) to the deeper regions of the confined space of SiO 2 . The catalytic performance is directly related to the presence of the nucleophilic Br anion on the outermost exposed layer of the hybrid material.
A family of dinuclear iron (II) compounds with iminopyridine-based ligands displays selective cytotoxic activity against cancer cell lines. All compounds have IC
values 2-6 fold lower than that of ...cisplatin, and 30-90 fold lower than that of carboplatin for the tumor cell lines assayed. Comparing the IC
values between tumor and non-tumor cell lines, the selectivity indexes range from 3.2 to 34, compound
, showing the highest selectivity. Those compounds carrying substituents on the iminopyridine ring show the same cytotoxicity as those without substituents. However, the electronic effects of the substituents on position 6 may be important for the cytotoxicity of the complexes, and consequently for their selectivity. All compounds act over DNA, promoting cuts on both strands in the presence of reactive oxygen species. Since compound
presented the highest selectivity, its cytotoxic effect was further characterized. It induces apoptosis, affects cell cycle phase distribution in a cell-dependent manner, and its cytotoxic effect is linked to reactive oxygen species generation. In addition, it decreases tumor cell migration, showing potential antimetastatic effects. These properties make compound
a good lead antitumor agent among all compounds studied here.
C–H benzylic oxidation promoted by dinuclear iron DBDOC iminopyridine complexes. Display omitted
Several benzofurobenzofuran and methanodibenzodioxocine iminopyridine derivatives have been used as ...ligands to form mononuclear and dinuclear iron complexes. Complexes 6, 7, 8, 9 and 10 were able to promote the catalytic oxidation of benzylic C–H bonds to ketones in moderate to high yields. The effects of backbone scaffold, nuclearity (mononuclear versus dinuclear) and nitrogen hybridization (iminopyridine versus aminopyridine) were studied. A strong effect on the yields of the nature and position of the substituents in the substrates was observed.
A series of new triazolium-based supported ionic liquids (SILPs), decorated with Cu NPs, were successfully prepared and applied to the N-arylation of aryl halides with anilines. The triazoles ...moieties were functionalised using copper-catalysed azide-alkyne cycloaddition. SILP surface characterisation showed a strong correlation between the triazolium cation volume and textural properties. STEM images showed well-dispersed Cu NPs on SILPs with a mean diameter varying from 3.6 to 4.6 nm depending on the triazolium cation used. Besides, XPS results suggest that the Cu(0)/Cu(
i
) ratio can be modulated by the electronic density of triazolium substituents. XPS and computational analysis gave mechanistic insights into the Cu NP stabilisation pathways, where the presence of electron-rich groups attached to a triazolium ring plays a critical role in leading to a cation adsorption pathway (
E
ads
= 72 kcal mol
−1
). In contrast, less electron-rich groups favour the anion adsorption pathway (
E
ads
= 63 kcal mol
−1
). The Cu@SILP composite with electron-rich groups showed the highest activity for the C-N Ullmann coupling reaction, which suggests that electron-rich groups might act as an electron-like reservoir to facilitate oxidative addition for N-arylation. This strategy firmly suggests the strong dependence of the nature of triazolium-based SILPs on the Cu NP surface active sites, which may provide a new environment to confine and stabilise MNPs for catalytic applications.
A series of new triazolium-based supported ionic liquids (SILPs), decorated with Cu NPs, were successfully prepared and applied to the
N
-arylation of aryl halides with anilines.
A series of imino- and amino-pyridine ligands based on dihydrobenzofurobenzofuran (BFBF) and methanodibenzodioxocine (DBDOC) backbones have been synthesized. These ligands form exclusively dinuclear ...complexes with metals such as iron(II) and copper(II). The structures for complexes 15, 16, 18, 19, 20, 21, 23, and 24 were determined by X-ray crystallography. The complexes show large distances for the metal nuclei and different geometries depending on the nature of the metal. An octahedral geometry was observed for the iron(II) complexes, while copper(II) complex 24 showed a distorted trigonal bipyramidal geometry. The iron(II) complexes showed activity as catalysts in the cycloaddition of CO2 to epoxides, obtaining moderate yields of cyclic carbonates.
The Cover Feature shows a Mn (I) complex as excellent catalyst for the transfer hydrogenation of ketones with 2‐propanol as hydrogen source. In their Communication, O. Martínez‐Ferraté et al. ...demonstrate that manganese complexes of readily accessible bidentate triazole ligands are effective catalysts for transfer hydrogenation of a broad range of substrates using iso‐propanol in presence of various bases including sodium hydroxide. The rapidly expanding structural variety of effective ligand frameworks makes cheap and benign Manganese a very attractive new arrow in the quiver of organometallic chemists. More information can be found in the Communication by O. Martínez‐Ferraté et al. on page 4514 in Issue 20, 2018 (DOI: 10.1002/cctc.201800953).
A series of first row metal complexes (Co, Ni and Cu) containing commercial nitrogen ligands were synthetized and used as catalyst in the cycloaddition of CO.sub.2 to epoxides. The reaction was ...carried out in ionic liquids based on 1-n-butyl-3-methylimidazolium as solvents. Best catalytic results were achieved with Co catalysts in 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMIm.BF.sub.4). Under optimized reaction conditions cyclic carbonates were selectively obtained with good to excellent yields, presenting a reliable alternative to synthetize the product using low cost and abundant catalytic system containing a common ligand as ethylenediamine. Finally, macrocycle effects where studied in each case comparing the conversion rates obtained by using ethylenediamine and 1,4,8,11-tetraazacyclotetradecane.
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