Oxidation of secondary alcohols byN-methylmorpholine-N-oxide (NMO) catalyzed by atrans-dioxo ruthenium(VI) complex or perruthenate complex: A kinetic study

Thetrans-dioxo ruthenium (VI) complex, [P(C₆H₅)₃C₆H₅CH₂]⁺[Ru(O)₂OAcCl₂] or tetrapropylammonium perruthenate catalyzes the oxidation of secondary alcohols to ketones byN-methylmorpholine-N-oxide (NMO). Kinetic studies showed the formation of a complex between catalyst and substrate (alcohol) as the first step in the mechanism.     

Synthesis of Benzo[a]heptalenes via Benzanellation–Aromatization Sequence

A novel approach towards the synthesis of functionalized benzo[a]heptalenes 9 and 10 via a 6π‐electrocyclic ring closure – aromatization sequence of corresponding bis[prop‐2‐enoates] 5 and 6 has been developed (Scheme 1). The starting bis[prop‐2‐enoates] have been prepared from the corresponding dialdehydes 3a and 4a in a Wittig‐Horner reaction, and their UV/VIS properties have also been investigated (Fig. 1 and Table 1). The dehydrogenations of the corresponding diols 1 and 2 to dialdehydes with a number of oxidizing reagents, including MnO₂ in CH₂Cl₂, tetrapropylammonium perruthenate (TPAP), and activated DMSO, have been studied in detail.     

Stabilization of catalytic sol-gel entrapped perruthenate

A combination of more stable counter-cation (tetraphenylphosphonium in place of tetrapropylammonium), of local basic microenvironment, and of a non-solubilizing reaction medium (supercritical CO₂) improves the life-cycle and reusability of catalytic ORMOSILs doped with perruthenate in the oxidation of alcohols with O₂. A number of different bases were co-entrapped and their effect on catalysis assessed in the oxidative dehydrogenation of benzyl alcohol in dense phase carbon dioxide at 22 MPa and 75 °C. The optimized catalyst retains most of its activity after five consecutive runs when a normal ORMOSIL-entrapped TPAP has become inactive. Deactivation of TPAP could be ascribed by EPR analysis to the formation of catalytically inactive RuO₂.     

Reductive alkylation of anhydrides and lactones: direct access to monosubstituted lactones

Reductive alkylation of anhydrides (1 equiv) with a 2:0.25 mixture of Grignard reagent and Zn(BH₄)₂ afforded monosubstituted lactones in moderate yields. The same sequence applied to unsubstituted lactones gave monoalkylated diols, which were further selectively oxidised with tetra-n-propylammonium perruthenate (TPAP) into the expected monoalkylated lactones.     

Alcohols oxidation with hydrogen peroxide promoted by TPAP-doped ormosils

Organically modified silica gels doped with TPAP (tetra-n-propylammonium perruthenate) are effective catalysts for the oxidation of alcohols by hydrogen peroxide at room temperature, provided that the oxidant H₂O₂ solution is added slowly. The effect of the surface catalyst polarity is the opposite of that found in aerobic alcohols oxidation and is consistent with the polar nature of the primary oxidant.     

NMO⋅TPB: A Selectivity Variation on the Ley–Griffith TPAP Oxidation

A non‐hygroscopic tetraphenylborate salt of N‐methylmorpholine‐N‐oxide (NMO) is reported (NMO ? TPB), which modulates the standard Ley–Griffith oxidation such that benzylic and allylic alcohols are oxidised selectively. An attractive feature of this new protocol is that anhydrous conditions are not required for this selective tetra‐n‐propylammonium perruthenate (TPAP) oxidation, superseding the requirement of molecular sieves.     

Synthesis and activity of aryl benzyl methyl sulfonium salts as cationic initiators: Effect of substituent on aryl group

Benzyl o-, m-, and p-substituted phenyl methyl sulfonium salts ( 2b – 2g ) were synthesized and their activities as cationic initiators were evaluated in the bulk polymerization of phenyl glycidyl ether (PGE). Especially, their activities were estimated with respect to the effect of substituents on the aryl groups. In the polymerizations of PGE with a series of benzyl p-substituted phenyl methyl sulfonium salts, the order of their activities was found to be 2c (CH₃OCOO) > 2b (CH₃COO) > 2d (CH₃O) ～ 2a (HO). In particular, 2c was the most active initiator of all, capable of initiating the polymerization of PGE even at room temperature. In the polymerizations with 2a, 2e (m-Cl), 2f (o-CH₃), and 2g (m-CH₃), the activity of 2e was the highest of all while those of 2a, 2f , and 2g were almost the same. These results strongly suggested that the electron-withdrawing group placed on the aryl group undoubtedly enhanced the activity of the sulfonium salts as the cationic initiators.     

MC-SCF and CI calculations on four isomers of Si6H6

The four isomers of Si₆ H₆, hexasilabenzene ( 1 ), hexasilaprismane ( 2 ), hexasila-Dewar benzene ( 3 ), and tris-(disilanediyl) ( 4 ), have been investigated, using highly correlated wavefunctions in conjunction with a local pseudopotential approach. At the Hartree-Fock level 1 (D_6h), 2 (D_3h), and 3 (C_2v) are established as minima by means of the harmonic vibrational frequencies. Inclusion of the most important correlation corrections via CI however, provokes a significant puckering of 1 resulting in a D_3d structure, 7.1 kJ/mol below the planar conformer. The detailed analysis shows unambiguously that the propensity to puckering is due solely to the correlation contributions from the σ framework while correlation of the π electrons is of little relevance. Isomer 2 turns out to be the most stable of the investigated isomers lying 41 kJ/mol below 1 (D_3d). Isomers 3 and 4 are more than 100 kJ/mol higher in energy. The Si? Si bond energies of 1 and 2 are determined as 251 and 176 kJ/mol, respectively.     

Density functional theory study of CO2 capture and storage promotion using manipulation of graphyne by 3d and 4d transition metals

In this work, the electronic and structural properties of 3d and 4d transition metal (TM)-decorated graphyne (GY) (TM-GY) toward CO₂ adsorption were studied using the D3-corrected density functional theory (DFT-D3) method. Then, CO₂ capture and storage (CCS) of the most stable structures were investigated. Results show that the most stable site for all TM decoration is the center of the 12-membered ring with various distances from carbon plane, and GY decorated with Ni and Zn from 3d and Zr and Cd from 4d TMs are also the most and the least stable, energetically with E_b of −5.834, −0.467, −6.181, and −0.963 eV, respectively. Evaluation of the adsorption behavior of CO₂ on TM-GY reveals that the strongest adsorption energies belong to Cr and Mo-GY (−1.502 and −1.117 eV, respectively), and for all 3d and 4d TMs, the horizontal direction of CO₂ is more stable, energetically. Increasing CO₂ molecules, step by step, on Cr and Mo-GY shows that they can hold 13 and 18 CO₂ molecules with average E_ads of −0.374 and −0.330 eV/CO₂ and corresponding CO₂ storage capacities of 47.66 and 54.10 wt%, respectively. These findings show that Cr and Mo-GY can be used in the future as suitable candidates for CCS applications.     

[RuCl3ind3] and [RuCl2ind4]: Two New Ruthenium Complexes derived from the Tumor‐inhibiting RuIII Compound HInd (OC‐6‐11)‐[RuCl4ind2] (ind = indazole)

Indazolium (OC‐6‐11)‐tetrachlorobis(indazole) ruthenate(III), HInd (OC‐6‐11)‐[RuCl₄ind₂], exhibits excellent results in different tumor models in vitro and in vivo. Substitution reactions of this ruthenium(III) complex are of special interest for a deeper understanding of its interactions with biologically occurring targets and its mode of action. The indazolium complex salt can be transformed to the neutral, meridionally configurated trisindazole complex (OC‐6‐21)‐[RuCl₃ind₃] in solvents like tetrahydrofuran. The X‐ray crystal structure of this complex could be solved (monoclinic space group P2(1)/n, a = 12.441(3), b = 10.415(3), c = 21.635(4) Å, β = 105.02(1)°). In spite of the paramagnetic Ru^III atom most of the coordinated indazole protons could be assigned with the help of two‐dimensional NMR experiments. Additionally, a reduced reaction product of HInd (OC‐6‐11)‐[RuCl₄ind₂] in the physiological solubilizer 2‐pyrrolidone could be isolated and the X‐ray crystal structure of this Ru^II complex, (OC‐6‐12)‐[RuCl₂ind₄], crystallized with two 2‐pyrrolidones, could be solved (monoclinic space group P2(1)/n, a = 12.139(2), b = 10.426(2), c = 14.426(3) Å, β = 100.06(3)°).     

Theoretical investigations on structure,density, detonation properties,and sensitivity of the derivatives of PYX

The ? NH₂, ? NO₂, ? N₃, ? NHNO₂, and ? ONO₂ substitution derivatives of PYX (2,6‐bis(picrylamino)‐3,5‐dinitropyridine) were studied at the B3LYP/6‐31G** level of density functional theory. The sublimation enthalpies and heats of formation (HOFs) in gas phase and solid state of these compounds were calculated. The theoretical predicted density (ρ), detonation pressure (P), and detonation velocity (D) showed that these derivatives have better detonation performance than PYX. The effects of substituent groups on HOF, ρ, P, and D were discussed. The order of contribution of various groups to P and D was ? ONO₂ > ? NO₂ > ? NHNO₂ > ? N₃ > ? NH₂. Sensitivity was evaluated using the frontier orbital energies, bond orders, bond dissociation enthalpies (BDEs), and characteristic heights (h₅₀). The trigger bonds in the pyrolysis process for these PYX derivatives may be Ring‐NO₂, NH? NO₂, or O? NO₂ varying with the substituents. The h₅₀ of most compounds are larger than that of CL‐20, and those of ? NH₂, ? NO₂, and most ? ONO₂ derivatives are larger than that of RDX. The BDEs of the trigger bonds of all but the ? ONO₂ derivatives are sufficiently large. Taking both detonation performance and sensitivity into consideration, some derivatives of PYX may be good candidates of explosives. © 2012 Wiley Periodicals, Inc.     

Tetraphenylphosphonium perosmate(VII) as an oxidant: comparison of [OsO4]− with [RuO4]−

Summary The osmium(VII) salt (Ph₄P)[OsO₄] functions as a stoichiometric oxidant for benzylic and allylic alcohols, oxidising primary alcohols to aldehydes and secondary alcohols to ketones. Its vibrational spectra and cyclic voltammetric behaviour are compared with those of the perruthenate ion, [RuO₄]^–.     

Disilicon Complexes with Two Hexacoordinate Si Atoms: Paddlewheel‐Shaped Isomers with (ClN4)Si?Si(S4Cl) and (ClN2S2)Si?Si(S2N2Cl) Skeletons

The reaction of 1‐methyl‐3‐trimethylsilylimidazoline‐2‐thione with hexachlorodisilane proceeds toward substitution of four of the disilane Cl atoms during the formation of disilicon complexes with two neighboring hexacoordinate Si atoms. The N,S‐bidentate methimazolide moieties adopt a buttressing role, thus forming paddlewheel‐shaped complexes of the type ClSi(μ‐mt)₄SiCl (mt=methimazolyl). Most interestingly, three isomers (i.e., with (ClN₄)Si? Si(S₄Cl), (ClN₃S)Si? Si(S₃NCl), and (ClN₂S₂)Si? Si(S₂N₂Cl) skeletons as so‐called (4,0), (3,1), and cis‐(2,2) paddlewheels) were detected in solution by using ²⁹Si NMR spectroscopic analysis. Two of these isomers could be isolated as crystalline solids, thus allowing their molecular structures to be analyzed by using X‐ray diffraction studies. In accord with time‐dependent NMR spectroscopy, computational analyses proved the cis‐(2,2) isomer with a (ClN₂S₂)Si? Si(S₂N₂Cl) skeleton to be the most stable. The compounds presented herein are the first examples of crystallographically evidenced disilicon complexes with two Si? Si‐bonded octahedrally coordinated Si atoms and representatives of the still scarcely explored class of Si coordination compounds with sulfur donor atoms.     

Thermal behavior of some new triazole derivative complexes

A series of new complexes with mixed ligands of the type [ML(C₃H₃O₂)₂]·nH₂O (((1) M=Mn, n=1; (2) M=Co(II), n=2; (3) M=Ni(II), n=4; (4) M=Cu(II), n=1.5; (5) M=Zn(II), n=0; L=3-amino-1,2,4-triazole and (C₃H₃O₂)=acrylate anion) were synthesized and characterised by chemical analysis and IR data. In all complexes the 3-amino-1,2,4-triazole acts as bridge while the acrylate acts as bidentate ligand except for complex (5) where it is found as unidentate. The thermal behaviour steps were investigated in nitrogen flow. The thermal transformations are complex processes according to TG and DTG curves including dehydration, acrylate ion and 3-amino-1,2,4-triazole degradation respectively. The final products of decomposition are the most stable metal oxides, except for complex (4) that leads to metallic copper.     

Preparation and in vitro investigations of triphenyl[ω‐(tetrahydro‐2H‐pyran‐2‐yloxy)alkyl]tin(IV) compounds

The reaction of SnPh₃Li with X(CH₂)_n O–THP (THP = tetrahydro‐2H ‐pyran‐2‐yl; n  = 3, 4, 6, 8, 11; X = Cl, Br) afforded organotin(IV) compounds with the general formula Ph₃Sn(CH₂)_n O–THP ( 1 – 5 ). The tetraorganotin(IV) compounds were characterized using multinuclear NMR and infrared spectroscopies and high‐resolution mass spectrometry. Anticancer activity of the synthesized compounds was tested in vitro against the A2780 (ovarian), A549 (lung), HeLa (adenocarcinoma) and SW480 (colon) tumour cell lines with SRB assay. The in vitro investigations revealed that when a shorter chain was present a higher activity was achieved; however compounds 1 – 5 were found to be less active than cisplatin. In addition, the most active compound, 1 , enters A2780 cells and causes apoptosis by triggering both intrinsic and extrinsic caspase pathways.     

Syntheses,Crystal Structures and Properties of the Tetrametaphosphimates MII2(PO2NH)4 · 8 H2O with MII = Mg,Mn, Co and Zn

Mg₂(PO₂NH)₄ · 8 H₂O ( 1 ), Mn₂(PO₂NH)₄ · 8 H₂O ( 2 ), Co₂(PO₂NH)₄ · 8 H₂O ( 3 ) and Zn₂(PO₂NH)₄ · 8 H₂O ( 4 ) were obtained as microcrystalline powders by combining aqueous solutions of K₄(PO₂NH)₄ · 4 H₂O and MX₂ · y H₂O (M = Mg, Mn, Co, Zn; X = Cl, NO₃). Single crystals were obtained by crystallization in gelatine gels in U‐tubes or test‐tubes. 2 and 4 were characterized by thermogravimetry and 4 was additionally characterized by temperature dependend in situ powder diffractometry. The structures of 1 , 2 , 3 and 4 were found to be isotypic and were solved by single‐crystal X‐ray methods: P 2₁/c, Z = 2 ( 1 : a = 645.4(2), b = 1050.1(2), c = 1283.3(3) pm, β = 104.66(3)°; 2 : a = 648.7(2), b = 1063.1(2), c = 1310.8(3) pm, β = 103.93(3)°; 3 : a = 643.3(2), b = 1049.0(2), c = 1286.7(3) pm, β = 104.28(3)°; 4 : a = 644.18(5), b = 1049.22(7), c = 1282.43(8) pm, β = 104.122(6)°). The structure is composed of MO₆ octahedra and (PO₂NH)₄^4— anions. The P₄N₄ rings of the (PO₂NH)₄^4— anions exhibit a slightly distorted chair conformation, which is supported by IR data and has been described by torsion angles, Displacement Asymmetry Parameters and Puckering Parameters. Via M²⁺ ions and hydrogen bonds, the tetrametaphosphimate anions are connected forming layers perpendicular to [100]. These layers are connected by hydrogen bonds.     

Photocatalytic Hydrogen Production Activity and Mechanism of New Nickel-Based Sulfur Complexes in Aqueous Solution

The development of industry and the increase in population have caused energy shortages and environmental pollution problems. Developing clean and storable new energy is identified as a key way to solve the problems above. Hydrogen is viewed as the most potential energy carrier due to its high calorific value and pollution-free. To convert solar energy into hydrogen energy, three nickel-based catalysts, Ni(aps)(pys)₂ (aps=2-amino-2-phenylacetic salicylaldehyde) ( 1 ), Ni(ads)(pys)₂ (ads=aniline salicylaldehyde, pys=pyridine-2-thiolate) ( 2 ), Ni(acs)(pys)₂ (acs=aniline 5-chlorosalicylaldehyde) ( 3 ), were synthesized and explored as photocatalysts for hydrogen production. A three-component photocatalytic system for hydrogen production was constructed using target complex as photocatalyst, triethanolamine (TEOA) as electron sacrificial agent and fluorescein (FL) as photosensitizer. Under the optimum conditions, about 1504 μmol of H₂ can be obtained with 25 mg catalyst 2 after 3 hours of irradiation. Finally, the hydrogen-production mechanism was discussed by experimental and theoretical methods.     

Derivatives of phosphorous acid as a new class of ligands for Pd-catalyzed allylation

Amido- and aminophosphites and hydrospirophosphoranes can be used as ligands in the Pd-catalyzed allylation of ethyl malonate with ethyl (3-phenylprop-2-enyl) carbonate. Bidentate ligands (RO)₂P--O(CH₂)_n--NR"₂ (n = 2 and 3) were found to be the most effective ligands.     

Transition metal complexes of nano bidentate organometallic Schiff base: Preparation,structure characterization,biological activity,DFT and molecular docking studies

An organometallic NO‐bidentate Schiff base, (2‐(1‐((1‐carboxyethyl)imino)ethyl) cyclopenta‐2,4‐dien‐1‐yl)(cyclopenta‐2,4‐dien‐1‐yl) iron (HL) was synthesized by condensation of 2‐acetylferrocene with amino acid alanine. Then its octahedral Cr (III), Mn (II), Fe (III), Co (II), Ni (II), Cu (II), Zn (II) and Cd (II) complexes were synthesized. All compounds were characterized on the basis of elemental analysis (C, H, N and M), molar conductivity, FT‐IR, UV–Vis, ¹H‐NMR, SEM, mass analysis and thermal studies. Furthermore, computational studies of HL ligand have been carried out by DFT/B3LYP method. HOMO and LUMO energy values, chemical hardness‐softness, electronegativity, electrophilic index and other parameters were calculated. SEM micrographs of HL ligand and its [Cd (HL)(H₂O)₂Cl₂].2H₂O complex, showed that they were prepared in nano‐structure forms with particle size 54 and 41 nm, respectively. Antifungal and antibacterial activities of HL ligand and its metal complexes have been screened in vitro against different species such as Aspergillus fumigatus, Candida albicans, Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Salmonella typhimurium. The synthesized compounds were evaluated for their anticancer activities against breast cancer cell line (MCF‐7) and normal melanocytes cell line (HFB‐4). It was found that [Co (HL)(H₂O)₂Cl₂].3H₂O complex had the lowest IC₅₀ value (10.9 μg/ml) and hence was the most active one. Finally, the optimized structures of the Schiff base and its Co (II) complex have been used to accomplish molecular docking studies with receptors of 3HB5, 3MIW, 5IBV and 4WM8 to determine the most preferred mode of interaction.