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Discrepancies regarding the coordination environment, donor atoms, nuclearity, and oxidation state of the active site of particulate methane monooxygenase (pMMO), a copper‐dependent enzyme capable of activating the strong C−H bond of methane, persist despite numerous structural and spectroscopic studies. To address the proposed mono‐ (CuII) or bimetallic (2CuI) nature of the so‐called CuB site, we report the bis(benzimidazole)‐based NMe−N,N'‐(1‐Me‐2‐CH2C7H4N2)2C6H4 ligand (N4) and its copper complexes. In the solid state [Cu(N4)(ClO4)]ClO4 features tetragonal geometry defined by the chelating ligand and an axial perchlorate; geometric and EPR parameters are very close to those reported for the CuB site. Attempts to obtain a dicopper(I) analog resulted in [Cu(N4)][CuCl2], based on spectroscopic, electrochemical, and ESI‐MS data. Although these results support the assignment of CuB as a monometallic site, air exposure of [Cu(N4)][CuCl2] leads to ligand oxidation in the structurally characterized [Cu(N4=O)Cl], raising the possibility of distorted tetragonal Cu(I) centers activating O2 and oxidizing substrates, in C−H activation chemistry that may take place at CuB. [ABSTRACT FROM AUTHOR]

By taking advantage of a sequence of oxidative addition/reductive elimination reactions, Pt(II) cyclometalated derivatives are able to promote a rare C(sp2)-C(sp3) bond coupling, resulting in the production of novel methyl-substituted pyridines and bipyridines. Starting from 6-phenyl-2,2′-bipyridine, the step-by-step full sequence of reactions has been followed, leading to the unprecedented 3-methyl-6-phenyl-2,2′-bipyridine, which was isolated and fully characterized. The synthesis involves the following steps: (1) rollover cyclometalation to give the starting complex [Pt(N^C)(DMSO)Me]; (2) the synthesis of a more electron-rich complex [Pt(N^C)(PPh3)Me] by the substitution of DMSO with triphenylphosphine; (3) oxidative addition with methyl iodide to give the Pt(IV) complex [Pt(N^C)(PPh3)(Me)2(I)]; (4) iodide abstraction with silver tetrafluoborate to give an unstable pentacoordinate intermediate, which rapidly evolves through a carbon–carbon reductive coupling, forming a new C(sp3)-C(sp2) bond; (5) finally, the extrusion and characterization of the newly formed 3-methyl-6-phenyl-2,2′-bipyridine. The reaction has been therefore extended to a well-known classical cyclometalating ligand, 2-phenylpyridine, demonstrating that the method is not restricted to rollover derivatives. Following the same step-by-step procedure, 2-phenylpyridine was converted to 2-o-tolyl-pyridine, displaying the potential application of the method to the larger family of classical cyclometalated complexes. The application of this protocol may be useful to convert an array of heterocyclic compounds to their methyl- or alkyl-substituted analogs. [ABSTRACT FROM AUTHOR]

A unique four‐coordinate, classical gold(I)‐carbonyl complex with substantial backdonation from gold has been isolated by using a B‐methylated and fluorinated tris(pyridyl)borate chelator. Its lighter silver(I) and copper(I) analogs enabled a study of trends in the coinage‐metal family. The B‐arylated ligand version also afforded a gold–carbon monoxide complex that displays a notably low C−O stretch value, but with trigonal planar geometry at the gold. A computational analysis shows that the AuI−CO bonds of these tris(pyridyl)borate ligand‐supported molecules consist of electrostatic attraction, OC→Au σ‐donation, and very significant Au→CO π‐back‐bonding components. The latter is responsible for the observed C−O stretching frequencies, which are lower than in free CO. [ABSTRACT FROM AUTHOR]

Two new luminescent ligands, 4‐(2‐pyridine)‐7‐methyl‐2,1,3‐benzothiadiazole (L1) and 4‐(2,2‐bipyridine)‐7‐methyl‐2,1,3‐benzothiadiazole (L2), based on 2,1,3‐benzothiadiazole and pyridine or bipyridine were obtained by Suzuki coupling reactions. DFT and TD‐DFT type calculations have been performed on L1 and L2 in order to assign their experimental UV‐visible and emission bands. Reaction of L1 and L2 with metal(II) chlorides (M=Zn, Mn, Cu) provided the neutral complexes of formulas [ZnL1Cl2] (1), [Zn(L1)2Cl2] (2), [ZnL2Cl2] (3), [MnL2Cl2] ⋅ 0,5CH2Cl2 (4) and [CuL2Cl2] ⋅ H2O (5) which have been structurally characterized. The Zn(II) ions in 1 and 2 are four‐coordinate in somewhat distorted tetrahedral N2Cl2 surroundings with L1 adopting bidentate (1) and monodentate (2) coordination modes. Complexes 3–5 are isostructural and their metal atoms are five‐coordinate in distorted square pyramidal environments with three nitrogen atoms from the tridentate L2 ligand and a chlorine building the basal plane and another chlorine atom occupying the apical position. The three Zn(II) complexes are strongly luminescent in solution and the solid state, while the cryomagnetic study of the paramagnetic compounds 4 and 5 in the temperature range 2.9–300 K shows a Curie‐Weiss behaviour typical of small antiferromagnetic interactions which are mediated by weak intermolecular contacts. [ABSTRACT FROM AUTHOR]

The rare earth element complexes (Ln=Y, La, Sm, Lu, Ce) of several podant κ6N‐coordinating ligands have been synthetized and thoroughly characterized. The structural properties of the complexes have been investigated by X‐ray diffraction in the solid state and by advanced NMR methods in solution. To estimate the donor capabilities of the presented ligands, an experimental comparison study has been conducted by cyclic voltammetry as well as absorption experiments using the cerium complexes and by analyzing 89Y NMR chemical shifts of the different yttrium complexes. In order to obtain a complete and detailed picture, all experiments were corroborated by state‐of‐the‐art quantum chemical calculations. Finally, coordination competition studies have been carried out by means of 1H and 31P NMR spectroscopy to investigate the correlation with donor properties and selectivity. [ABSTRACT FROM AUTHOR]

Two mononuclear nickel(II) complexes of the formula [Ni(terpyCOOH)2](ClO4)2∙4H2O (1) and [Ni(terpyepy)2](ClO4)2 MeOH (2) [terpyCOOH = 4′-carboxyl-2,2′:6′,2″-terpyridine and terpyepy = 4′-[(2-pyridin-4-yl)ethynyl]-2,2′:6′,2″-terpyridine] have been prepared and their structures determined by single-crystal X-ray diffraction. Complexes 1 and 2 are mononuclear compounds, where the nickel(II) ions are six-coordinate by the six nitrogen atoms from two tridentate terpy moieties. The mean values of the equatorial Ni-N bond distances [2.11(1) and 2.12(1) Å for Ni(1) at 1 and 2, respectively, are somewhat longer than the axial ones [2.008(6) and 2.003(6) Å (1)/2.000(1) and 1.999(1) Å (2)]. The values of the shortest intermolecular nickel–nickel separation are 9.422(1) (1) and 8.901(1) Å (2). Variable-temperature (1.9–200 K) direct current (dc) magnetic susceptibility measurements on polycrystalline samples of 1 and 2 reveal a Curie law behavior in the high-temperature range, which corresponds to magnetically isolated spin triplets, the downturn of the χMT product at lower temperatures being due to zero-field splitting effects (D). Values of D equal to −6.0 (1) and −4.7 cm−1 (2) were obtained through the joint analysis of the magnetic susceptibility data and the field dependence of the magnetization. These results from magnetometry were supported by theoretical calculations. Alternating current (ac) magnetic susceptibility measurements of 1 and 2 in the temperature range 2.0–5.5 K show the occurrence of incipient out-phase signals under applied dc fields, a phenomenon that is characteristic of field-induced Single-Molecule Magnet (SMM) behavior, which herein concerns the 2 mononuclear nickel(II) complexes. This slow relaxation of the magnetization in 1 and 2 has its origin in the axial compression of the octahedral surrounding at their nickel(II) ions that leads to negative values of D. A combination of an Orbach and a direct mechanism accounts for the field-dependent relation phenomena in 1 and 2. [ABSTRACT FROM AUTHOR]

[Display omitted] • The first regioselective palladium(II)-catalyzed alkoxy-aryloxycarbonylation of olefins is described. • Various olefins, alcohols and phenols have been converted into the corresponding mixed alkyl-aryl succinates in one-step, with yields up to 90%, under mild reaction conditions (4 bar of CO and 20 °C). • The selectivity of the process has been explained by means of DFT calculations. • The unexpected role of the oxidant benzoquinone, in promoting the final elimination step leading to the succinic product, has been identified. The direct alkoxy-aryloxycarbonylation reaction of olefins has been realized for the first time. Under palladium(II) catalysis and with p -benzoquinone as oxidant, various olefins (aromatic, aliphatic and 1,2-disubstituted), alcohols (primary, secondary and tertiary) and phenols (with different para , meta and ortho substituents) have been converted in one-step into mixed alkyl aryl succinates in moderate to excellent yields (up to 90%). The reaction is completely regioselective, as the aryl ester moiety was consistently observed on the more substituted carbon of the starting alkene double bond. Based on experimental results and detailed DFT calculations, a plausible catalytic cycle has been proposed, accounting for the observed regioselectivity. Interestingly, from our computation studies, benzoquinone was found to be crucial not only to regenerate the catalytic active species, but also for promoting the final elimination step, leading to the desired succinate. Finally, some reactions were performed to prove the different chemical behavior of the two installed ester groups. [ABSTRACT FROM AUTHOR]

By taking advantage of a sequence of oxidative addition/reductive elimination reactions, Pt(II) cyclometalated derivatives are able to promote a rare C(sp2)-C(sp3) bond coupling, resulting in the production of novel methyl-substituted pyridines and bipyridines. Starting from 6-phenyl-2,2′-bipyridine, the step-by-step full sequence of reactions has been followed, leading to the unprecedented 3-methyl-6-phenyl-2,2′-bipyridine, which was isolated and fully characterized. The synthesis involves the following steps: (1) rollover cyclometalation to give the starting complex [Pt(N^C)(DMSO)Me]; (2) the synthesis of a more electron-rich complex [Pt(N^C)(PPh3)Me] by the substitution of DMSO with triphenylphosphine; (3) oxidative addition with methyl iodide to give the Pt(IV) complex [Pt(N^C)(PPh3)(Me)2(I)]; (4) iodide abstraction with silver tetrafluoborate to give an unstable pentacoordinate intermediate, which rapidly evolves through a carbon–carbon reductive coupling, forming a new C(sp3)-C(sp2) bond; (5) finally, the extrusion and characterization of the newly formed 3-methyl-6-phenyl-2,2′-bipyridine. The reaction has been therefore extended to a well-known classical cyclometalating ligand, 2-phenylpyridine, demonstrating that the method is not restricted to rollover derivatives. Following the same step-by-step procedure, 2-phenylpyridine was converted to 2-o-tolyl-pyridine, displaying the potential application of the method to the larger family of classical cyclometalated complexes. The application of this protocol may be useful to convert an array of heterocyclic compounds to their methyl- or alkyl-substituted analogs.

The equilibrium of copper-catalyzed atom transfer radical polymerization was investigated in silico with the aim of finding an explanation for the experimentally observed solvent effect. Various combinations of alkyl halide initiators and copper complexes in acetonitrile (MeCN) and dimethyl sulfoxide (DMSO) were taken into consideration. A continuum model for solvation, which does not account for the explicit interactions between the solvent and metal complex, is not adequate and does not allow the reproduction of the experimental trend. However, when the solvent molecules are included in the coordination sphere of the copper(I,II) species and the continuum description of the medium is still used, a solvent dependence of process thermodynamics emerges, in fair agreement with experimental trends. [ABSTRACT FROM AUTHOR]

Rollover cyclometalated complexes constitute a family of derivatives which differ from classical cyclometalated species in certain aspects. Various potential application fields have been developed for both classes of compounds, which have both similarities and differences. In order to uncover the relationships and distinctions between these two families of compounds, four Pt(II) cyclometalated complexes derived from 2-phenylpyridine (ppy) and 2,2′-bipyridine (bpy), assumed as prototypical ligands, were compared. For this study, an electron rich isostructural and isoelectronic pair of compounds, [Pt(N^C)Me(PPh3)], and an electron-poorer compound, [Pt(N^C)Cl(PPh3)] were chosen (N^C = ppy or bpy). DFT calculations, cyclic voltammetry, and UV-Vis spectra also helped to shed light into these species. Due to the presence of the more electronegative nitrogen in place of a C-H group, the rollover bpy-H ligand becomes a slightly weaker donor than the classical ppy-H ligand, and hence, generates (slightly) more stable cyclometalated complexes, lower energy frontier molecular orbitals, and electron-poorer platinum centers. On the whole, it was revealed that classical and rollover complexes have overall structural similarity, which contrasts to their somewhat different chemical behavior. [ABSTRACT FROM AUTHOR]

Catalysts generated by combinations of Pd(TFA)2 and pyridine‐hydrazone ligands have been applied to 1,2 addition of arylboronic acids to aliphatic N‐carbamoyl (Cbz) hydrazones, affording protected α‐aryl monoalkylhydrazines with high enantioselectivities (37‐99% ee). Subsequent removal of the benzyloxy carbonyl protecting group provides a direct entry to free monosubstituted hydrazines, key building blocks for the synthesis of appealing 1,2‐diaza‐heterocycles, aminoacid derived hydrazides and other pharmacophores thereof. [ABSTRACT FROM AUTHOR]

Two mononuclear nickel(II) complexes of the formula [Ni(terpyCOOH)2](ClO4)2∙4H2O (1) and [Ni(terpyepy)2](ClO4)2 MeOH (2) [terpyCOOH = 4′-carboxyl-2,2′:6′,2″-terpyridine and terpyepy = 4′-[(2-pyridin-4-yl)ethynyl]-2,2′:6′,2″-terpyridine] have been prepared and their structures determined by single-crystal X-ray diffraction. Complexes 1 and 2 are mononuclear compounds, where the nickel(II) ions are six-coordinate by the six nitrogen atoms from two tridentate terpy moieties. The mean values of the equatorial Ni-N bond distances [2.11(1) and 2.12(1) Å for Ni(1) at 1 and 2, respectively, are somewhat longer than the axial ones [2.008(6) and 2.003(6) Å (1)/2.000(1) and 1.999(1) Å (2)]. The values of the shortest intermolecular nickel–nickel separation are 9.422(1) (1) and 8.901(1) Å (2). Variable-temperature (1.9–200 K) direct current (dc) magnetic susceptibility measurements on polycrystalline samples of 1 and 2 reveal a Curie law behavior in the high-temperature range, which corresponds to magnetically isolated spin triplets, the downturn of the χMT product at lower temperatures being due to zero-field splitting effects (D). Values of D equal to −6.0 (1) and −4.7 cm−1 (2) were obtained through the joint analysis of the magnetic susceptibility data and the field dependence of the magnetization. These results from magnetometry were supported by theoretical calculations. Alternating current (ac) magnetic susceptibility measurements of 1 and 2 in the temperature range 2.0–5.5 K show the occurrence of incipient out-phase signals under applied dc fields, a phenomenon that is characteristic of field-induced Single-Molecule Magnet (SMM) behavior, which herein concerns the 2 mononuclear nickel(II) complexes. This slow relaxation of the magnetization in 1 and 2 has its origin in the axial compression of the octahedral surrounding at their nickel(II) ions that leads to negative values of D. A combination of an Orbach and a direct mechanism accounts for the field-dependent relation phenomena in 1 and 2.

To suppress the over-oxidation of solvents, reaction conditions were optimized, and ligands were added to the system to facilitate the oxidation of sulfur compounds with molecular oxygen. The addition of suitable nitrogen ligands led to effective suppression, and 2,2'-bipyridine showed the best performance among the analyzed samples. After the use of the ligand, the yields of by-products from solvent oxidation were reduced by a factor of 15 compared to those from the reaction without any ligands. [ABSTRACT FROM AUTHOR]

Three 2,1,3-benzothiadiazole-based ligands decorated with two pyridyl groups, 4,7-di(2-pyridyl)-2,1,3-benzothiadiazol (2-PyBTD), 4,7-di(3-pyridyl)-2,1,3-benzothiadiazol (3-PyBTD) and 4,7-di(4-pyridyl)-2,1,3 benzothiadiazol (4-PyBTD), generate ZnII and AgI complexes with a rich structural variety: [Zn(hfac)2(2-PyBTD)] 1, [Zn2(hfac)4(2-PyBTD)] 2, [Ag(CF3SO3)(2-PyBTD)]23, [Ag(2-PyBTD)]2(SbF6)24, [Ag2(NO3)2(2-PyBTD)(CH3CN)] 5, [Zn(hfac)2(3-PyBTD)] 6, [Zn(hfac)2(4-PyBTD)] 7, [ZnCl2(4-PyBTD)2] 8 and [ZnCl2(4-PyBTD)] 9 (hfac = hexafluoroacetylacetonato). The nature of the resulting complexes (discrete species or coordination polymers) is influenced by the relative position of the pyridyl nitrogen atoms, the nature of the starting metal precursors, as well as by the synthetic conditions. Compounds 1 and 8 are mononuclear and 2, 3 and 4 are binuclear species. Compounds 6, 7 and 9 are 1D coordination polymers, while compound 5 is a 2D coordination polymer, the metal ions being bridged by 2-PyBTD and nitrato ligands. The solid-state architectures are sustained by intermolecular π–π stacking interactions established between the pyridyl group and the benzene ring from the benzothiadiazol moiety. Compounds 1, 2, 7–9 show luminescence in the visible range. Density Functional Theory (DFT) and Time Dependent Density Functional Theory (TD-DFT) calculations have been performed on the ZnII complexes 1 and 2 in order to disclose the nature of the electronic transitions and to have an insight on the modulation of the photophysical properties upon complexation.

Copper(I) halide complexes are well sought-after materials due to their rich structural diversities and photophysical properties. Profoundly, there is a direct relationship between each structural variation and luminescence of these complexes, for a purported use. In this review, recent publications within the last 2 years about copper(I) halide complexes, centering on their structural dimensionalities with derivatives of nitrogen, phosphorus, and sulfur ligands, have been considered alongside their effects on luminescence.

Rollover cyclometalated complexes constitute a family of derivatives which differ from classical cyclometalated species in certain aspects. Various potential application fields have been developed for both classes of compounds, which have both similarities and differences. In order to uncover the relationships and distinctions between these two families of compounds, four Pt(II) cyclometalated complexes derived from 2-phenylpyridine (ppy) and 2,2′-bipyridine (bpy), assumed as prototypical ligands, were compared. For this study, an electron rich isostructural and isoelectronic pair of compounds, [Pt(N^C)Me(PPh3)], and an electron-poorer compound, [Pt(N^C)Cl(PPh3)] were chosen (N^C = ppy or bpy). DFT calculations, cyclic voltammetry, and UV-Vis spectra also helped to shed light into these species. Due to the presence of the more electronegative nitrogen in place of a C-H group, the rollover bpy-H ligand becomes a slightly weaker donor than the classical ppy-H ligand, and hence, generates (slightly) more stable cyclometalated complexes, lower energy frontier molecular orbitals, and electron-poorer platinum centers. On the whole, it was revealed that classical and rollover complexes have overall structural similarity, which contrasts to their somewhat different chemical behavior.

Aiming at extending the tagged zinc bipyrazolate metal–organic frameworks (MOFs) family, the ligand 3,3'‐diamino‐4,4'‐bipyrazole (3,3'‐H2L) has been synthesized in good yield. The reaction with zinc(II) acetate hydrate led to the related MOF Zn(3,3'‐L). The compound is isostructural with its mono(amino) analogue Zn(BPZNH2) and with Zn(3,5‐L), its isomeric parent built with 3,5‐diamino‐4,4'‐bipyrazole. The textural analysis has unveiled its micro‐/mesoporous nature, with a BET area of 463 m2 g−1. Its CO2 adsorption capacity (17.4 wt. % CO2 at pCO2 = 1 bar and T = 298 K) and isosteric heat of adsorption (Qst = 24.8 kJ mol−1) are comparable to that of Zn(3,5‐L). Both Zn(3,3'‐L) and Zn(3,5‐L) have been tested as heterogeneous catalysts in the reaction of CO2 with the epoxides epichlorohydrin and epibromohydrin to give the corresponding cyclic carbonates at T = 393 K and pCO2 = 5 bar under solvent‐ and co‐catalyst‐free conditions. In general, the conversions recorded are higher than those found for Zn(BPZNH2), proving that the insertion of an extra amino tag in the pores is beneficial for the epoxidation catalysis. The best catalytic match has been observed for the Zn(3,5‐L)/epichlorohydrin couple, with 64 % conversion and a TOF of 5.3 mmol(carbonate) (mmolZn)−1 h−1. To gain better insights on the MOF‐epoxide interaction, the crystal structure of the [epibromohydrin@Zn(3,3'‐L)] adduct has been solved, confirming the existence of Br⋅⋅⋅(H)−N non‐bonding interactions. To our knowledge, this study represents the first structural determination of a [epibromohydrin@MOF] adduct. [ABSTRACT FROM AUTHOR]

The iron(II) complexes [Fe(bpy)3](OTf)2 (bpy = 2,2'-bipyridine; OTf = CF3SO3) (1) and [Fe(bpydeg)3](OTf)2 (bpydeg = N4,N4-bis(2-(2-methoxyethoxy)ethyl) [2,2'-bipyridine]-4,4'-dicarboxamide) (2), the latter being a newly synthesized ligand, were employed as catalyst precursors for the oxidation of 1-phenylethanol with hydrogen peroxide in water, using either microwave or conventional heating. With the same oxidant and medium the oxidation of glycerol was also explored in the presence of 1 and 2, as well as of two similar iron(II) complexes bearing tridentate ligands, i.e., [Fe(terpy)2](OTf)2 (terpy = 2, 6-di(2-pyridyl)pyridine) (3) and [Fe(bpa)2](OTf)2 (bpa = bis(2-pyridinylmethyl)amine) (4): in most reactions the major product formed was formic acid, although with careful tuning of the experimental conditions significant amounts of dihydroxyacetone were obtained. Addition of heterocyclic amino acids (e.g., picolinic acid) increased the reaction yields of most catalytic reactions. The effect of such additives on the evolution of the catalyst precursors was studied by spectroscopic (NMR, UV-visible) and ESI-MS techniques.

Reliable methods for enantioselective cis‐dihydroxylation of trisubstituted alkenes are scarce. The iron(II) complex cis‐α‐[FeII(2‐Me2‐BQPN)(OTf)2], which bears a tetradentate N4 ligand (Me2‐BQPN=(R,R)‐N,N′‐dimethyl‐N,N′‐bis(2‐methylquinolin‐8‐yl)‐1,2‐diphenylethane‐1,2‐diamine), was prepared and characterized. With this complex as the catalyst, a broad range of trisubstituted electron‐deficient alkenes were efficiently oxidized to chiral cis‐diols in yields of up to 98 % and up to 99.9 % ee when using hydrogen peroxide (H2O2) as oxidant under mild conditions. Experimental studies (including 18O‐labeling, ESI‐MS, NMR, EPR, and UV/Vis analyses) and DFT calculations were performed to gain mechanistic insight, which suggested possible involvement of a chiral cis‐FeV(O)2 reaction intermediate as an active oxidant. This cis‐[FeII(chiral N4 ligand)]2+/H2O2 method could be a viable green alternative/complement to the existing OsO4‐based methods for asymmetric alkene dihydroxylation reactions. [ABSTRACT FROM AUTHOR]

Reliable methods for enantioselective cis‐dihydroxylation of trisubstituted alkenes are scarce. The iron(II) complex cis‐α‐[FeII(2‐Me2‐BQPN)(OTf)2], which bears a tetradentate N4 ligand (Me2‐BQPN=(R,R)‐N,N′‐dimethyl‐N,N′‐bis(2‐methylquinolin‐8‐yl)‐1,2‐diphenylethane‐1,2‐diamine), was prepared and characterized. With this complex as the catalyst, a broad range of trisubstituted electron‐deficient alkenes were efficiently oxidized to chiral cis‐diols in yields of up to 98 % and up to 99.9 % ee when using hydrogen peroxide (H2O2) as oxidant under mild conditions. Experimental studies (including 18O‐labeling, ESI‐MS, NMR, EPR, and UV/Vis analyses) and DFT calculations were performed to gain mechanistic insight, which suggested possible involvement of a chiral cis‐FeV(O)2 reaction intermediate as an active oxidant. This cis‐[FeII(chiral N4 ligand)]2+/H2O2 method could be a viable green alternative/complement to the existing OsO4‐based methods for asymmetric alkene dihydroxylation reactions. [ABSTRACT FROM AUTHOR]

Reliable methods for enantioselective cis‐dihydroxylation of trisubstituted alkenes are scarce. The iron(II) complex cis‐α‐[FeII(2‐Me2‐BQPN)(OTf)2], which bears a tetradentate N4 ligand (Me2‐BQPN=(R,R)‐N,N′‐dimethyl‐N,N′‐bis(2‐methylquinolin‐8‐yl)‐1,2‐diphenylethane‐1,2‐diamine), was prepared and characterized. With this complex as the catalyst, a broad range of trisubstituted electron‐deficient alkenes were efficiently oxidized to chiral cis‐diols in yields of up to 98 % and up to 99.9 % ee when using hydrogen peroxide (H2O2) as oxidant under mild conditions. Experimental studies (including 18O‐labeling, ESI‐MS, NMR, EPR, and UV/Vis analyses) and DFT calculations were performed to gain mechanistic insight, which suggested possible involvement of a chiral cis‐FeV(O)2 reaction intermediate as an active oxidant. This cis‐[FeII(chiral N4 ligand)]2+/H2O2 method could be a viable green alternative/complement to the existing OsO4‐based methods for asymmetric alkene dihydroxylation reactions. [ABSTRACT FROM AUTHOR]

Reliable methods for enantioselective cis‐dihydroxylation of trisubstituted alkenes are scarce. The iron(II) complex cis‐α‐[FeII(2‐Me2‐BQPN)(OTf)2], which bears a tetradentate N4 ligand (Me2‐BQPN=(R,R)‐N,N′‐dimethyl‐N,N′‐bis(2‐methylquinolin‐8‐yl)‐1,2‐diphenylethane‐1,2‐diamine), was prepared and characterized. With this complex as the catalyst, a broad range of trisubstituted electron‐deficient alkenes were efficiently oxidized to chiral cis‐diols in yields of up to 98 % and up to 99.9 % ee when using hydrogen peroxide (H2O2) as oxidant under mild conditions. Experimental studies (including 18O‐labeling, ESI‐MS, NMR, EPR, and UV/Vis analyses) and DFT calculations were performed to gain mechanistic insight, which suggested possible involvement of a chiral cis‐FeV(O)2 reaction intermediate as an active oxidant. This cis‐[FeII(chiral N4 ligand)]2+/H2O2 method could be a viable green alternative/complement to the existing OsO4‐based methods for asymmetric alkene dihydroxylation reactions. [ABSTRACT FROM AUTHOR]

Anchoring a homogeneous catalyst onto a heterogeneous support facilitates separation of the product from the catalyst, and catalyst‐substrate interactions can also modify reactivity. Herein we describe the synthesis of composite materials comprising carbon nitride (g‐C3N4) as the heterogeneous support and the well‐established homogeneous catalyst moiety [Cp*IrCl]+ (where Cp*=η5‐C5Me5), commonly used for catalytic hydrogenation. Coordination of [Cp*IrCl]+ to g‐C3N4 occurs directly at exposed edge sites with a κ2N,N' binding motif, leading to a primary inner coordination sphere analogous to known homogeneous complexes of the general class [Cp*IrCl(NN‐κ2N,N')]+ (where N,N'=a bidentate nitrogen ligand). Hydrogenation of unsaturated substrates using the composite catalyst is selective for terminal alkenes, which is attributed to the restricted steric environment of the outer coordination sphere at the edge‐sites of g‐C3N4. [ABSTRACT FROM AUTHOR]

A cyclic (alkyl)(amino)carbene (CAAC) has been shown to react with a covalent azide similar to the Staudinger reaction. The reaction of MeCAAC with trimethylsilyl azide afforded the N‐silylated 2‐iminopyrrolidine (MeCAAC=NSiMe3), which was fully characterized. This compound undergoes hydrolysis to afford the 2‐iminopyrrolidine and trimethylsiloxane which co‐crystallize as a hydrogen‐bonded adduct. The N‐silylated 2‐iminopyrrolidine was used to transfer the novel pyrrolidine‐2‐iminato ligand onto both main‐group and transition‐metal centers. The reaction of the tetrabromodiborane bis(dimethyl sulfide) adduct with two equivalents of MeCAAC=NSiMe3 afforded the disubstituted diborane. The reaction of MeCAAC=NSiMe3 with TiCl4 and CpTiCl3 afforded MeCAAC=NTiCl3 and MeCAAC=NTiCl2Cp, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • We have examined the electronic structure of nitrogen (N) for Co-N x -C SACs. • In-situ NEXAFS flow cell incorporating a polymer exchange membrane are used. • Persistent N-ligand under cathodic potential contributed to the distinct electronic structure of Co-N x -C. • Slight variations observed in Co during reaction could be attributed to the adsorption of chemicals. Single atom catalysts (SACs) anchored to N-carbon (M-Nx-C) have been extensively investigated owing to their impressive catalytic activity and relatively low cost. In contrast to the bulk catalysts, M-Nx-C almost maintain their oxidation states even under the cathodic potentials, displaying only minor adjustments in its pristine electronic structure. In this context, we have examined the electronic structure of nitrogen through in-situ/operando NEXAFS to unveil the origin of the distinct electronic configuration of M-Nx-C. We were able to observe the behavior of N, which significantly influences the state of SACs. When exposed to conditions resembling hydrogen evolution reactions, the electronic structure of cobalt exhibited slight changes, while the electronic configuration of the nitrogen ligands remained largely intact. Through a combination of in-situ/operando NEXAFS investigation and insights from prior literature, we hypothesized that the sustained electronic structure of M-Nx-C can be attributed to the inherent stability of the nitrogen ligands under the cathodic potentials. Moreover, any subtle shifts in the cobalt state appeared to result from chemical adsorption rather than modifications to the nitrogen ligands, such as protonation. Our study contributes valuable insights into the functional role of nitrogen ligands in M-Nx-C, thereby bolstering the findings of previous theoretical and experimental studies. [ABSTRACT FROM AUTHOR]

Dianionic N,N-chelating ligands play a crucial role in coordination chemistry, but reports on related complexes remain limited to certain types of ligands. In here, the reactions of two diprotic ligands, i.e., a biguanide and a carbothiamide, with trimethylaluminium, are reported, which give rise to mono- and dinuclear aluminium(III) complexes. In addition, single deprotonation of the diprotic biguanide using potassium bis(trimethylsilyl)amide gives rise to a one-dimensional coordination polymer. All complexes have been fully characterized, and their solid-state structures were determined by single crystal X-ray diffraction analysis.

Four new compounds of formulas [Cu(hfac)2(L)] (1), [Ni(hfac)2(L)] (2), [{Cu(hfac)2}2(µ-L)]·2CH3OH (3) and [{Ni(hfac)2}2(µ-L)]·2CH3CN (4) [Hhfac = hexafluoroacetylacetone and L = 3,6-bis(picolylamino)-1,2,4,5-tetrazine] have been prepared and their structures determined by X-ray diffraction on single crystals. Compounds 1 and 2 are isostructural mononuclear complexes where the metal ions [copper(II) (1) and nickel(II) (2)] are six-coordinated in distorted octahedral MN2O4 surroundings which are built by two bidentate hfac ligands plus another bidentate L molecule. This last ligand coordinates to the metal ions through the nitrogen atoms of the picolylamine fragment. Compounds 3 and 4 are centrosymmetric homodinuclear compounds where two bidentate hfac units are the bidentate capping ligands at each metal center and a bis-bidentate L molecule acts as a bridge. The values of the intramolecular metal···metal separation are 7.97 (3) and 7.82 Å (4). Static (dc) magnetic susceptibility measurements were carried out for polycrystalline samples 1–4 in the temperature range 1.9–300 K. Curie law behaviors were observed for 1 and 2, the downturn of χMT in the low temperature region for 2 being due to the zero-field splitting of the nickel(II) ion. Very weak [J = −0.247(2) cm−1] and relatively weak intramolecular antiferromagnetic interactions [J = −4.86(2) cm−1] occurred in 3 and 4, respectively (the spin Hamiltonian being defined as H = −JS1·S2). Simple symmetry considerations about the overlap between the magnetic orbitals across the extended bis-bidentate L bridge in 3 and 4 account for their magnetic properties.

Formation of the O−O bond is considered the critical step in oxidative water cleavage to produce dioxygen. High‐valent metal complexes with terminal oxo (oxido) ligands are commonly regarded as instrumental for oxygen evolution, but direct experimental evidence is lacking. Herein, we describe the formation of the O−O bond in solution, from non‐heme, N5‐coordinate oxoiron(IV) species. Oxygen evolution from oxoiron(IV) is instantaneous once meta‐chloroperbenzoic acid is administered in excess. Oxygen‐isotope labeling reveals two sources of dioxygen, pointing to mechanistic branching between HAT (hydrogen atom transfer)‐initiated free‐radical pathways of the peroxides, which are typical of catalase‐like reactivity, and iron‐borne O−O coupling, which is unprecedented for non‐heme/peroxide systems. Interpretation in terms of [FeIV(O)] and [FeV(O)] being the resting and active principles of the O−O coupling, respectively, concurs with fundamental mechanistic ideas of (electro‐) chemical O−O coupling in water oxidation catalysis (WOC), indicating that central mechanistic motifs of WOC can be mimicked in a catalase/peroxidase setting. [ABSTRACT FROM AUTHOR]

• Benzotriazole is an ideal molecule for the synthesis of coordination compounds. • A review on the use of benzotriazole and its derivatives as ligands in coordination chemistry. • The compounds are listed according to the linker and its role in the architecture. • Structural, magnetic, catalytic and luminescent applications are discussed. With the use of N -donor ligands in coordination chemistry receiving significant interest and attention in the last few decades, benzotriazole has emerged as an ideal molecule that provides many synthetic advantages and reliable routes towards polynuclear coordination clusters and coordination polymers. In order to fully realise this potential, the current work provides a systematic study of the recent advances on the use of benzotriazole and its derivatives as ligands in coordination chemistry. The reported complexes have been primarily categorized in regards to the exact linker used and its role in the resulting architecture (either as a main or as a secondary ligand). Important structural information, as well as notable properties (such as magnetism, catalysis, luminescence, bio-applications) are also mentioned for the compounds. [ABSTRACT FROM AUTHOR]

Abstract In recent years, considerable effort has been focused in Pd catalyzed cross-coupling reactions, especially the use of less reactive and economically viable substrates like aryl chlorides. Unfortunately, Pd complexes containing the ligands having only N as a donor atom has some limitations, as it couples, mostly aryl iodides and bromides with different nucleophiles, and shows less activity towards aryl chlorides. This restriction can overwhelm by the use of Pd complexes containing N in combination with the C as a donor atom such as palladacycles, pincers, PEPPSI and carbene ligands. The advantages of these ligands include high activity with enhanced selectivity, less toxicity, moisture, air as well as thermal stability. Most importantly, such complexes have broad applications in catalysis under ambient conditions. This part of compressive review highlights the results of the highly active C N based Pd complexes and their applications in cross-coupling reactions. In the next part, we will cover all ligands and complexes containing N in combination with P, O and S as a donor atoms (Pd catalysts based on C P, C O and C S ligands). Though, the number of C N based Pd complexes containing Ferrocene and Buchwald ligands were reported for Pd catalyzed cross-coupling reaction, these complexes will be covered in the next part of the article. Graphical abstract Image 1 Highlights • Pd catalyzed cross coupling reaction of compounds containing C N bonds. • Update of the recent efforts made in the coupling reactions by Pd complexes based on the C N ligands. • The present part focused on the applications of the ligands containing C N as donor atoms. • Next part covers all ligands and catalysts containing N in combination with O, P and S as a donor atoms. [ABSTRACT FROM AUTHOR]

Abstract Oxidation of primary and secondary alcohols, including two diols and glycerol, with H 2 O 2 was catalyzed by the iron(II) complexes [FeL 3 ](OTf) 2 (L = 2,2′-bipyridine, 2,2′-bipyrimidine, 1,10-phenanthroline and substituted derivatives) and [FeL 2 ](OTf) 2 (L = bis(2-pyridinylmethyl)amine, 2,6-di(2-pyridyl)pyridine). The reactions were performed in acetonitrile, water or mixed solvent (typically water/acetonitrile 4:1) in a microwawe reactor at low power. Effect of addition of a cocatalyst, which in some cases improved the yields of the catalytic reaction, was investigated by means of NMR and UV–Visible techniques. Graphical abstract The iron(II) complexes [FeL 3 ](OTf) 2 (L = 2,2′-bipyridine, 2,2′-bipyrimidine, 1,10-phenanthroline and substituted derivatives) and [FeL 2 ](OTf) 2 (L = bis(2-pyridinylmethyl)amine, 2,6-di(2-pyridyl)pyridine) are competent catalysts for microwave-assisted oxidation of alcohols. Addition of some heterocyclic aminoacids as cocatalysts improved the reaction yields; the effect of such additives was studied by NMR and UV–Visible spectroscopies. Image 1 Highlights • Highly sustainable oxidation due to choice of oxidant, solvents and MW heating. • Iron-based catalysts with simple, commercial nitrogen ligands. • Water or water/organic solvent as green reaction medium. • Improved reaction yields by addition of some aminoacids as cocatalysts. • Spectroscopic (NMR, UV–Visible) studies on the effect of cocatalyst. [ABSTRACT FROM AUTHOR]

The synthesis, solid state characterization, theoretical and experimental photoluminescence studies of two new important classes of binuclear lanthanide complexes: [Ln 2 (Ibf) 6 (4,4'-dmbpy) 2 ] Eu = 1 , Gd = 2 and Tb = 3 ) and [Ln 2 (Ibf) 6 (5,5'-dmbpy) 2 ] Eu = 4 , Gd = 5 and Tb = 6 ) (where: Ibf = non – steroidal anti – inflammatory drug (NSAID) Ibuprofen, 4,4'-dmbpy and 5,5'-dmbpy are 4,4'-dimethyl-2,2'-bipyridine and 5,5'-dimethyl-2,2'-bipyridine , respectively) are reported in this work. The analytical and spectroscopic data suggest the formation of binuclear compounds. The RM1 model was used to obtain the molecular structures of the Eu III complexes and its optimized ground state geometries were used to calculated all details involved in the energy transfer process and compared with experimental data, being in an optimal agreement. The lowest ligand triplet state (T 1 ) in these systems were obtained through of the time – resolved phosphorescence spectra, proving that the intramolecular energy transfer is responsible by high photoluminescence in these compounds. Still, the values of energy of the centroid of the 5 D 0 → 7 F 0 transition for the Eu III complexes, indicate an increase in the covalence degree for the Eu – L bonds, which is due to inductive effect (+I) of the –CH 3 groups in the ancillary ligands, when compared with those [Eu 2 (Ibf) 6 (bpy) 2 ] recently published. The high values of quantum efficiency and solubility in common organic solvents can opens the possibility to test this binuclear compounds in the field of efficient luminescent devices and biomarkers. [ABSTRACT FROM AUTHOR]

An 8-step, gram-scale synthesis of the (−)-sparteine surrogate (22 % yield, with just 3 chromatographic purifications) and a 10-step, gram-scale synthesis of (−)-sparteine (31 % yield) are reported. Both syntheses proceed with complete diastereocontrol and allow access to either antipode. Since the syntheses do not rely on natural product extraction, our work addresses long-term supply issues relating to these widely used chiral ligands. [ABSTRACT FROM AUTHOR]

The Pd catalyzed cross coupling reactions of compounds containing C-X bonds (C-I, C-Br, C-Cl, C-N, C-O and C-H) with a variety of nucleophiles is one of the most efficient and reliable approachs for the construction of new C-C and C-heteroatom bonds. In recent years, great achievements have been made in this field, and many powerful catalytic systems based on ligand design have been developed. This comprehensive review covers recent effort made in the constructions of C-C and C-heteroatom bonds through Pd complexes based on the N ligands. We divided this topic into two parts. In present part we have focused on the applications of the ligands containing only N as a donor atom. In the next part we will cover all ligands and complexes containing N in combination with C, P, O and S as a donor atom. [ABSTRACT FROM AUTHOR]

The complexes [Zn(phenylacetato)2(2-aminopyridin)2] (3), [Zn(phenylacetato)2(1,10-phenanthroline)]·H2O (4), and [Zn(phenylacetato)2(2,9-dimethyl-1,10-phenanthroline)]·0.5 H2O (5) were prepared and characterized by IR-, UV–Visible, 1H and 13C NMR spectroscopy, and single crystal X-ray diffraction. BNPP hydrolysis of the complexes and their parent nitrogen ligands showed that the hydrolysis rate of bis-(4-nitrophenyl) phosphate (BNPP) was 1.7 × 105 L mol−1 s−1 for 3, 3.1 × 105 L mol−1 s−1 for 4 and 4.3 × 104 L mol−1 s−1 for 5. Antibacterial activities show the effect of complexation on activity against Gram-positive (S. epidermidis, S. aureus, E. faecalis, M. luteus and B. subtilis) and Gram-negative (K. pneumonia, E. coli, P. mirabilis and P. aeruginosa) bacteria using the agar well diffusion method. Complex 4 showed good activity against G− bacteria except P. aeruginosa, and against G+ bacteria except E. ferabis. Complex 5 showed no activity against G− bacteria, low activity against M. luteus and B. subtilis bacteria and high activity against S. epidemidis and S. aureus. Complex 3 did not show any activity against G− or G+ bacteria. [ABSTRACT FROM AUTHOR]

The benzene, CO, and PPh 3 adducts [HB(3-(CF 3 ),5-(Ph)Pz) 3 ]AgL (L = C 6 H 6 , CO, or PPh 3 ) have been synthesized by a metathesis process using [HB(3-(CF 3 ),5-(Ph)Pz) 3 ]Na(THF), CF 3 SO 3 Ag, and the corresponding co-ligands. These silver(I) adducts have been characterized by NMR spectroscopy, and by X-ray crystallography. In all cases the Scorpionate is bound to silver in typical κ 3 -fashion. The X-ray crystallographic data of [HB(3-(CF 3 ),5-(Ph)Pz) 3 ]Ag(η 2 -C 6 H 6 ) show that it has a η 2 -bound benzene molecule. NMR data point to fluxional behavior in solution. The 13 C NMR resonance corresponding to the CO moiety of [HB(3-(CF 3 ),5-(Ph)Pz) 3 ]Ag(CO) appears as a single peak at δ 177.4 ppm and the ν ¯ co is observed at 2148 cm −1 . These values indicate the presence of a fairly Lewis acidic silver atom in [HB(3-(CF 3 ),5-(Ph)Pz) 3 ]Ag(CO) and significantly diminished Ag → CO π-backbonding. Interesting coupling is observed in the solution 19 F and 31 P NMR spectra of the Ag(I) adduct [HB(3-(CF 3 ),5-(Ph)Pz) 3 ]Ag(PPh 3 ). A detailed analysis of the spectral and structural features of these complexes has been described herein. [ABSTRACT FROM AUTHOR]

This work presents the synthesis, solid state characterization and complete photoluminescence study of three new important classes of lanthanide complexes containing the non-steroidal anti-inflammatory drug (NSAID) Ibuprofen. The analytical and spectroscopic data reveals the formation of nine complexes with the general formula [Ln(Ibf) 3 (H 2 O) 2 ] , [Ln 2 (Ibf) 6 (bpy) 2 ] and [Ln 2 (Ibf) 6 (phen) 2 ] (Ln=Eu III , Gd III and Tb III , Ibf=Ibuprofen ligand, bpy=2,2′- bipyridine and phen=1,10-phenanthroline). The molecular structures of the Eu III complexes were calculated using the RM1 model, and your optimized ground state geometries were used to calculated all details involved in the energy transfer process and compared with experimental data. The phosphorescence measurements of the Gd III complexes, allowed the identification of the lowest ligand triplet state, proving that the photoluminescence in the Eu III and Tb III Ibuprofen complexes is proposed to be a ligand sensitized luminescence process. The presence of N,N-donors (bpy or phen) in the structure of the Eu III Ibuprofen complexes results in an 3 to 4-fold increase in the quantum efficiency when compared with the Eu III complex without N,N-donors ligands. The high emission quantum efficiency ( η =69–80%) for Eu III complexes showed that they can be potential candidates as emitters in biologic assays. [ABSTRACT FROM AUTHOR]

The rare earth element complexes (Ln=Y, La, Sm, Lu, Ce) of several podant κ 6 N-coordinating ligands have been synthetized and thoroughly characterized. The structural properties of the complexes have been investigated by X-ray diffraction in the solid state and by advanced NMR methods in solution. To estimate the donor capabilities of the presented ligands, an experimental comparison study has been conducted by cyclic voltammetry as well as absorption experiments using the cerium complexes and by analyzing 89 Y NMR chemical shifts of the different yttrium complexes. In order to obtain a complete and detailed picture, all experiments were corroborated by state-of-the-art quantum chemical calculations. Finally, coordination competition studies have been carried out by means of 1 H and 31 P NMR spectroscopy to investigate the correlation with donor properties and selectivity., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Twelve new imidazole-based potential bi- and tridentate ligands were synthesized and characterized. Whereas in the first series the α-amino acid and imidazole moieties were linked by an amino bond, in the second series the tridentate ligands, containing two imidazole groups, were separated by an amide bond. The first series was obtained by the reductive amination of 2-phenylimidazole-4-carboxaldehyde with α-amino acid esters. The tridentate ligands were prepared from 2-phenylimidazole-4-carboxylic acid and chiral amines. In the Henry reaction, the amines were revealed as a more reactive species than the less nucleophilic amides, however the enantiomeric excesses were generally poor.

A convenient new synthesis for complexes of VOF 2 with N-donor ligands is via the reaction of VF 4 with the ligand in water, either under reflux or using hydrothermal conditions. The complexes, mer -[VOF 2 (terpy)]·3H 2 O (terpy = 2,2′6′,2‴-terpyridyl), [VOF 2 (bipy)(H 2 O)], [VOF 2 (phen)(H 2 O)], [VOF 2 (py) 2 (H 2 O)], [VOF 2 (py) 2 (H 2 O)]·H 2 O, [V 2 O 2 F 4 (py) 4 ] and [pyH] 2 [V 2 O 2 F 6 (H 2 O) 2 ], along with the O-donor, pyridine N-oxide (pyNO) complex, [V 2 O 2 F 4 (H 2 O) 2 (pyNO) 2 ], have been isolated and characterised. The controlled hydrolysis of VF 4 in water produces the hydrate [VOF 2 (H 2 O) 2 ]·H 2 O. The complex [VOF 2 (Me 3 tacn)] (Me 3 tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane) was prepared by the reaction of [VOF 2 (py) 2 (H 2 O)] and Me 3 tacn in MeCN. The new complexes have been characterised by microanalysis and single crystal X-ray diffraction. Powder X-ray diffraction (PXRD) data were recorded for the bulk samples and compared with the PXRD patterns simulated from the single crystal data to confirm that the latter were representative of the bulk products. All the complexes contain six-coordinate vanadium(IV), with extensive H-bonding and (in the pyridyl ligand complexes) π-stacking interactions present. IR and UV–visible spectroscopic data and magnetic measurements are also reported and discussed. Attempts to obtain phosphine oxide or ether complexes by similar routes were unsuccessful. Unless the temperature is carefully controlled, the hydrothermal route yields mixtures of V IV and V V complexes. [ABSTRACT FROM AUTHOR]

Tris(pyrazolyl)borate (scorpionate) ligands can be considered as the most prolific ligands in contemporary coordination chemistry due to the availability of various steric and electronic substituents at the pyrazolyl rings that allow fine-tuning of the open-coordination site for metal centres. The thallium(I) complexes of anionic tridentate-chelating scorpionate ligands, namely [tris(3-mesityl-5-methyl-1 H-pyrazol-1-yl-κ N2)hydroborato]thallium(I) monohydrate, [Tl(C39H46BN6)]·H2O, (I), and [bis(3-mesityl-5-methyl-1 H-pyrazol-1-yl-κ N2)(5-mesityl-3-methyl-1 H-pyrazol-1-yl-κ N2)hydroborato]thallium(I), [Tl(C39H46BN6)], (II), show a {TlIN3} coordination, with average TlI-N bond lengths of 2.53 and 2.55 Å in (I) and (II), respectively. The overall TlI coordination geometry is distorted trigonal pyramidal, with the average N-TlI-N angle being approximately 73° for both. The dihedral angle between the planes of the pyrazolyl and benzene rings of the mesityl group is 82° in (I), while the corresponding angles in (II) are in the range 64-104°. The structural differences between the two ligands are expected to contribute to the different reactivities of the transition metal coordination complexes towards activation of small molecules such as dioxygen and ethylene. [ABSTRACT FROM AUTHOR]

An advantageous methodology for the oxidative debenzylation of ethers has been developed. Very low amounts of a catalyst system based on vanadyl acetylacetonate and a triazole type pincer ligand allow the selective oxidative cleavage of a number of O-benzyl ethers in the presence of oxygen as the sole oxidant. The methodology tolerates a number of functional groups such as halo-, alkoxy-, or trifluoromethylarenes, alkyne, alkene, ether, and acetal units. Large-scale deprotections can be also carried out by the optimized procedure, which is amenable to enantioenriched reactants as well. [ABSTRACT FROM AUTHOR]

The iron(II) complexes [Fe(N-N) 3 ](OTf) 2 (N-N = 2,2′- bipyridine, 1,10-phenanthroline and substituted derivatives) were employed as catalyst precursors for the oxidation of primary and secondary alcohols, including glycerol. The single-crystal structure of [Fe(bipy) 3 ](OTf) 2 was determined by X-ray crystallography.The catalytic reactions were performed using either H 2 O 2 or tert -butilhydroperoxide (TBHP) as oxidating agent, in mild experimental conditions: with all catalysts employed, secondary alcohols were oxidized to the corresponding ketones with up to 100% yields, whereas other substrates gave lower conversions. Indications on the nature of the catalytically active species, which is probably formed via dissociation of a nitrogen ligand from the iron center, were obtained from NMR and ESI–MS spectra. [ABSTRACT FROM AUTHOR]