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The complexes of copper [Cu(κ ONN ’-HL)(NO 3 )(DMF)](NO 3 )∙H 2 O ( 1 ) and [Cu(κ ONN ’-HL)Cl 2 ]∙½DMSO ( 2 ), and of manganese [Mn(κ ON -HL) 2 Cl 2 ]Cl ( 3 ) and [Mn(κ ON -HL) 2 (NO 3 ) 2 ](NO 3 )∙H 2 O ( 4 ) were synthesized by reactions of the respective chloride or nitrate salt with a non-aqueous solutions of the Schiff base aminoalcohol HL (product of condensation of salicylic aldehyde and aminoethylpiperazine) and characterized by X-ray diffraction analysis. The catalytic investigations disclosed a prominent activity of the copper compounds 1 and 2 towards oxidation of cyclohexane with hydrogen peroxide in the presence of various promoters (nitric, hydrochloric, oxalic acids and pyridine), under mild conditions. The unusual promoting effect of pyridine on the catalytic activity of the copper catalysts allowed to achieve yields up to 21% based on cyclohexane. Chromatographic studies revealed that cyclohexyl hydroperoxide is a main reaction product and chlorocyclohexane (in the presence of HCl as promoter) was also detected, suggesting a free radical reaction pathway with hydroxyl radicals as attacking species. Complexes 1 and 2 act also as catalysts in the oxidation of 1-phenylethanol with tert -butylhydroperoxide, showing acetophenone yields up to 62% and TON (turnover numbers) up to 620 in the presence of the K 2 CO 3 promoter. [ABSTRACT FROM AUTHOR]

Heterogeneous catalysts were prepared by covalent bonding of transition-metal salicylaldimine complex to α-zirconium phosphate, abbreviated as {α-ZrP.M(salicylaldimine) where M = Co, Mn and Cu}. The resulting compounds were characterized by BET surface area, TGA analysis, X-ray diffraction, Scanning electron micrograph, energy dispersive X-ray analysis, Fourier transform infrared and Atomic absorption spectroscopy. The catalytic activity of α-ZrP.M(salicylaldimine) was studied for the liquid phase oxidation of cyclohexane using tert -butylhydroperoxide as an oxidant under solvent free condition. In the oxidation reaction, cyclohexane was oxidized to cyclohexanol, cyclohexanone and some unidentified products. It was found that the reactivity of α-ZrP.M(salicylaldimine) catalyst for the oxidation reaction decreased in the order α-ZrP.Co(salicylaldimine) > α-ZrP.Mn(salicylaldimine) > α-ZrP.Cu(salicylaldimine). A maximum conversion of cyclohexane (14.18%) and selectivity of cyclohexanol (4.99%), cyclohexanone (87.34%) and some other products (7.67%) was observed for catalyst, α-ZrP.Co(salicylaldimine) after 6 h at 353 K. The catalyst, α-ZrP.Co(salicylaldimine) was reused for four cycles without significant loss of catalytic activity. [ABSTRACT FROM AUTHOR]

Silica nanoparticles (SiNPs) with the average size of 8.4 nm have been synthesized and functionalized with the reaction of Cl-sulfonylphenylethyl tri-methoxysilane. These functionalized SiNPs have been anchored in scorpionate compounds i.e., [CuCl 2 {HOCH 2 C(pz) 3 }], [V OCl 2 {HOCH 2 C(pz) 3 }], and [V(acac) {HOCH 2 C(pz) 3 }] as hybrid nano-catalysts. The presence of metal compound over support was confirmed with FTIR, EPR, TGA, TEM, XRD, AAS, and TEM–EDS. These catalysts have produced remarkable high TONs ca. 1216–2607 with yields 13.7–27.3% for the selective oxidation of cyclohexane ( Cy-hx ) with molecular oxygen under relatively mild conditions. Very high about 95% products selectivity of Cy = O and Cy-OH was also attained. The TGA analysis indicates that all the catalysts were thermally stable under operating reaction temperature and reusable up to five more cycles. [ABSTRACT FROM AUTHOR]

Highlights: [•] Synthesis of methoxysilane Schiff-base pentacoordinate metal complexes. [•] Immobilized complexes into HMS as supported catalysts. [•] Gas–liquid phase O2 oxidation of cyclohexane. [•] High catalytic TONs and product selective. [•] Proposed reaction mechanism. [Copyright &y& Elsevier]

Highlights: [•] Using more accessible 8-quinolinolato iron(III) (Q3FeIII) complexes to catalyze the selective oxidation of organic compounds by hydrogen peroxide. [•] Important substituent's effect of the Q3FeIII catalyst on their oxidative activity. [•] Significant and outstanding accelerating effect of visible light on the Q3FeIII-catalyzed oxidations. [Copyright &y& Elsevier]

Abstract: The oxovanadium(IV) complexes [VO(acac)2(Hpz)]·HC(pz)3 1·HC(pz)3 (acac=acetylacetonate, Hpz=pyrazole, pz=pyrazolyl) and [VOCl2{HOCH2C(pz)3}] 2 were obtained from reaction of [VO(acac)2] with hydrotris(1-pyrazolyl)methane or of VCl3with 2,2,2-tris(1-pyrazolyl)ethanol. The compounds were characterized by elemental analysis, IR, Far-IR and EPR spectroscopies, FAB or ESI mass-spectrometry and, for 1, by single crystal X-ray diffraction analysis. 1 and 2 exhibit catalytic activity for the oxidation of cyclohexane to the cyclohexanol and cyclohexanone mixture in homogeneous system (TONs up to 1100) under mild conditions (NCMe, 24h, room temperature) using benzoyl peroxide (BPO), tert-butyl hydroperoxide (TBHP), m-chloroperoxybenzoic acid (mCPBA), hydrogen peroxide or the urea-hydrogen peroxide adduct (UHP) as oxidants. 1 and 2 were also immobilized on a polydimethylsiloxane membrane (1-PDMS or 2-PDMS) and the systems acted as supported catalysts for the cyclohexane oxidation using the above oxidants (TONs up to 620). The best results were obtained with mCPBA or BPO as oxidant. The effects of various parameters, such as the amount of catalyst, nitric acid, reaction time, type of oxidant and oxidant-to-catalyst molar ratio, were investigated, for both homogeneous and supported systems. [Copyright &y& Elsevier]

Abstract: 3-(2-Hydroxy-4-nitrophenylhydrazo)pentane-2,4-dione (H2L, 1) was synthesized by azocoupling of diazonium salts of 2-hydroxy-4-nitroaniline with pentane-2,4-dione and shown to exist in the hydrazone tautomeric form in the free state and in its new dicopper(II) complex [Cu2(H2O)2(μ-L)2] (2) whose X-ray crystal structure was determined. Complex 2 acts as a catalyst, under mild conditions, for the peroxidative oxidation (with H2O2) of cyclohexane to cyclohexanol, cyclohexanone and cyclohexyl hydroperoxide, in MeCN/H2O, and for the aerobic TEMPO-mediated selective oxidation of benzylic alcohols to the corresponding aldehydes, thus showing that azoderivatives of β-diketones can be the suitable ligands for such types of reactions. [Copyright &y& Elsevier]

Abstract: The monomer transition metal complexes; [ML] (M=Mn(II), Co(II), Ni(II) and Cu(II)) have been synthesized from the reaction of metal acetate with bis(salicyaldehyde)oxaloyldihydrazone, H2L; in 1:1 molar ratio in ethanol under reflux. In all of the complexes, the principal dihydrazone ligand has been suggested to coordinate to the metal centres in the anti-cis-configuration. The complexes (Co(II), Ni(II) and Cu(II)) are suggested to have four-coordinate square-planar stereochemistry while the Mn(II) complex is suggested to have tetrahedral stereochemistry. These metal complexes with tetradendate Schiff-base ligand was entrapped in the nanocavity of zeolite-Y by a two-step process in the liquid phase: (i) adsorption of [bis(salicylaldiminato)metal(II)]; [M(sal)2]-NaY; in the supercages of the zeolite, and (ii) in situ Schiff condensation of the metal(II) precursor complex with oxaloyldihydrazone; [ML]-NaY. The new Host–Guest Nanocomposite Materials (HGNM) was characterized by several techniques: chemical analysis, spectroscopic methods (DRS, NMR, BET, FTIR and UV/vis), conductometric and magnetic measurements. The catalytic activities for oxidation of cyclohexane with HGNM and neat were reported. [Copyright &y& Elsevier]

Abstract: Oxovanadium(IV), copper(II) and nickel(II) complexes of Schiff base derived from salicylaldehyde and o-aminobenzyl alcohol (H2sal-oaba) have been encapsulated in the nano-pores of zeolite-Y by flexible ligand method and characterised by metal analysis, spectroscopic (IR and electronic) studies, scanning electron micrographs, thermal analysis and X-ray diffraction patterns. The encapsulated complexes abbreviated here as [VO(sal-oaba)(H2O)]-Y, [Cu(sal-oaba)(H2O)]-Y and [Ni(sal-oaba)(H2O)3]-Y catalyse the oxidation of styrene, cyclohexane and methyl phenyl sulfide using H2O2 as oxidant in good yield. Styrene catalysed by [VO(sal-oaba)(H2O)]-Y, [Cu(sal-oaba)(H2O)]-Y under optimised reaction conditions gave five reaction products namely, styrene oxide, benzaldehyde, 1-phenylethane-1,2-diol, benzoic acid and phenylacetaldehyde, while [Ni(sal-oaba)(H2O)3]-Y gave benzaldehyde selectively. In the presence of tert-butylhydroperoxide all catalysts gave styrene oxide in major yield, though overall conversion has been found low (10–30%). The oxidation products of cyclohexane are cyclohexanone and cyclohexanol. A maximum of 93.2% conversion of methyl phenyl sulfide has been achieved with [VO(sal-oaba)(H2O)]-Y using H2O2 as oxidant, where selectivity of sulfoxide was 96.9%. Other catalysts were inactive towards the oxidation of methyl phenyl sulfide while neat complex [VO(sal-oaba)] has been found to be equally active. [Copyright &y& Elsevier]

Abstract: N,N′-Bis(salicylidene)cyclohexane-1,2-diamine (H2sal-dach) reacts with oxovanadium(IV) and copper(II) exchanged zeolite-Y in refluxing methanol to yield the corresponding zeolite-Y encapsulated metal complexes, abbreviated herein as [VO(sal-dach)]-Y and [Cu(sal-dach)]-Y. Spectroscopic studies (IR, electronic and 1H NMR), thermal analysis, scanning electron micrographs (SEM) and X-ray diffraction patterns have been used to characterise these complexes. These encapsulated complexes catalyse the oxidation, by H2O2, of styrene, cyclohexene and cyclohexane efficiently in good yield. Under the optimized conditions, the oxidation of styrene catalysed by [VO(sal-dach)]-Y and [Cu(sal-dach)]-Y gave 94.6 and 21.7% conversion, respectively, where styreneoxide, benzaldehyde, benzoic acid, 1-phenylethane-1,2-diol and phenylacetaldehyde being the major products. Oxidation of cyclohexene catalysed by these complexes gave cyclohexeneoxide, 2-cyclohexene-1-ol, cyclohexane-1,2-diol and 2-cyclohexene-1-one as major products. Conversion of cyclohexene achieved was 86.6% with [VO(sal-dach)]-Y and 18.1% with [Cu(sal-dach)]-Y. A maximum of 78.1% conversion of cyclohexane catalysed by [Cu(sal-dach)]-Y and only 21.0% conversion by [VO(sal-dach)]-Y with major reaction products of cyclohexanone, cyclohexanol and cyclohexane-1,2-diol have been obtained. [Copyright &y& Elsevier]