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A series of known metal complexes, [LaL2(NO3)(H2O)2]·5H2O (1), [Zn(μ-L)(NO3)(H2O)]n (2), {[Cd2(μ-HL)(μ-L)(NO3)3(H2O)]·H2O}n (3) and [Hg(μ-L)(N3)]n·nH2O (4), were synthesized from the corresponding metal salts and 2-pyridinecarboxaldehyde isonicotinoylhydrazone (HL), and demonstrated high activity and selectivity in the cyanosilylation of aldehydes. Although all the complexes are derived from the same HL hydrazone ligand, the catalytic activity of 1–4 is different and relates to the metal center and coordination environment, whereas complex 1 being the most effective homogeneous Lewis acid-base catalyst towards the synthesis of cyanohydrin trimethylsilyl ethers from both aliphatic and aromatic aldehydes with yields up to 96.3 % in 6 h in methanol solution and at room temperature. According to the proposed mechanism, both coordination and noncovalent interactions (hydrogen and tetrel bonds) play a significant role and account for the higher catalytic activity of complex 1.

This review describes how non-covalent interactions, such as hydrogen (inter- and intramolecular, resonance- and charge-assisted hydrogen bonding), halogen, chalcogen and pnicogen bonds, π-interactions, as well as other types of weak forces can influence and control the reactions in the synthesis, e.g., of metal-containing supramolecular networks, providing a class of highly directional stabilizing contacts that can be exploited in the design of coordination compounds. The selected recent examples show that both inter- and intramolecular non-covalent interactions can influence the formation of coordination compounds. This overview of non-covalent interactions applied for synthesis and design of coordination compounds also contributes to an improved understanding of their behavior in crystal engineering, catalysis, etc. It provides a practical consultation for synthetic chemists that are interested in exploring and further developing non-covalent interactions assisted synthesis and design of coordination compounds.

The new 1D copper(II) coordination polymers (CPs) [Cu(μ-L1)(H2O)]n (1, H2L1 = 2-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl)benzoic acid) and [Cu(μ-H2L2)(H2O)]n (2, H4L2 = (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazinyl)terephthalic acid) and the known zwitterionic 1D CP [Cu2(H2O)2(μ-H2L3)(μ-L3)]n (3, H3L3 = 2-(2-(4,4-dimethyl-2,6-dioxocyclo-hexylidene)hydrazinyl)terephthalic acid) were synthesized and tested as homogeneous catalysts for cyanosilylation of a variety of aldehydes to the corresponding cyanohydrin trimethylsilyl ethers. Among these polymeric catalysts, 3, with a zwitterionic charater, is the most effective one, giving 86–99% yield of the ethers upon reaction of aliphatic and aromatic aldehydes with trimethylsilyl cyanide in methanol at room temperature in 4 h. Non-covalent interactions (cation-π and tetrel bondings) involving the aldehyde substrate are proposed to assist the cyanosilylation reaction.

Sodium 2-(2-(1-cyano-2-oxopropylidene)hydrazinyl)benzenesulfonate (NaHL) was synthesized by azocoupling of diazonium salt of 2-aminobenzenesulfonic acid with 3-oxobutanenitrile and characterized by IR, 1H and 13C NMR spectroscopies and ESI-MS analysis. In dimethylsulfoxide-d6 solution NaHL exists as a mixture of Z- and E-hydrazone forms in the amounts of 96 and 4%, respectively. Treatment of this isomeric mixture with copper(II) nitrate hydrate in the presence of ethylenediamine (en) provides unusual (E,Z) → E switching of NaHL to give [Cu(H2O)2(en)2](HL)2 (1). The process is interpreted on the basis of cooperative ionic interactions and resonance assisted hydrogen bonding (RAHB) → charge assisted hydrogen bonding (CAHB) transition.

Chemical transformations induced by mechanical force in solids are remarkable since they facilitate syntheses that are normally difficult to achieve in solution and thus allow the preparation of new molecules and materials or drastic improvements of the yields and selectivities. In many cases, the noncovalent interactions (NCIs) with mechanochemical treatment differ significantly from those which occur in analogous solvent-assisted processes. Moreover, if a “mechanocatalyst” is introduced into the system, it can additionally alter the NCIs, bond energies and properties of the reaction intermediates. As result, the outcome of many mechanocatalytic reactions can be very different in terms of efficiency or even reaction pathways compared with the traditional solution-based procedures or noncatalytic mechanochemical processes. Accordingly, in this chapter, certain mechanocatalytic reactions in which the NCIs play a key role are overviewed and discussed. Additionally, an overview of some experimental techniques used to study mechanochemical activation and the respective NCIs is also provided.

Thiazole derived compounds have great potential in medicinal- and agro-chemistries, catalysis, cosmetic industry, corrosion protection, light harvesting, production of light-emitting diodes (LEDs), photochromes and molecular switches or nonlinear optical materials. In spite of that, not much attention has been paid to the coordination chemistry of this class of versatile and polyfunctional heterocyclic ligands. This review intends to systematize the existing information in this field and to highlight some perspectives in the synthesis and applications of 1,3-thiazole, isothiazole and thiadiazole metal complexes.

Two complexes with isoindole-core ligands of general formula [M{C6H4C(NH2)NC(ONCMe2)2}2](NO3)2 (M = Co for 1 and M = Ni for 2) were studied as catalysts for the mild stereoselective alkane oxidation with m-chloroperbenzoic acid (m-CPBA) as an oxidant and cis-1,2-dimethylcyclohexane (cis-1,2-DMCH) as a main model substrate. Complex 1 disclosed a pronounced activity, with high retention of stereoconfiguration of substrates (>98% for cis-1,2-DMCH) and highest cis/trans ratio of tertiary alcohols (products) of 56, under mild conditions. The best achieved yields of tertiary cis-alcohols were of 13.7 and 50.5%, based on the substrate (cis-1,2-DMCH) and the oxidant (m-CPBA) respectively. Kinetic experiments, high bond and stereoselectivity parameters, kinetic isotope effect of 7.2(2) in the oxidation of cyclohexane, and incorporation of 18O from H218O support the involvement of CoIVO high-valent metal–oxo intermediates as main C–H attacking species.

The interaction of sodium(I) and copper(II) with sodium (E,Z)-2-[2-(1-cyano-2-methoxy-2-oxoethylidene)hydrazinyl]benzenesulfonate (NaHL1), sodium 4-[2-(2,4-dioxopentan-3-ylidene)hydrazinyl]benzenesulfonate (NaHL2), and sodium 2-[2-(2,4-dioxopentan-3-ylidene)hydrazinyl]benzenesulfonate (NaHL3) is studied on the basis of competition between intra- and intermolecular hydrogen bonding and coordination. The interplay between such interactions provides an unprecedented strategy towards an easy ((E,Z)E or Z) isomeric resolution of NaHL1 to give the new coordination polymers [Na(H2O)2(μ-HL1)]n (1) (E form) and [Na2(H2O)4(μ-HL1)2]n⋅nH2O (2) (Z form). It is also applied to the synthesis of the new compounds [Cu(H2O)6](HL2)2⋅4 H2O (3) and [Cu(A)L3]⋅H2O (4) (A=2-(pyridin-2-yl)ethanol). The intra- and intermolecular structural relevance of hydrogen bonding is detailed by X-ray diffraction.

In spite of its impressive record in medicinal chemistry, the role of barbituric acid H 3 BA (pyrimidine-2,4,6(1 H ,3 H ,5 H )-trione) in coordination, organometallic and supramolecular chemistries has not yet been analyzed and reviewed. However, H 3 BA can be readily functionalized and provides rich opportunities to create coordination bonds and non-covalent interactions. Thus, derivatives of H 3 BA (barbituric acids, BAs) are widely used for the preparation of a wide range of complexes with various metals of almost all groups of the periodic table. The review systematizes information on the synthesis, tautomerism, acid–base properties of BAs and their use for the construction of organometallic and coordination compounds, as well as coordination polymers and supramolecular assemblies. The role of different metal ions and the structure of BAs in directing the preparative pathways and tuning particular structural properties of the resulting compounds are discussed. Some valuable applications of BAs, in particular in the construction of molecular receptors, magnetic and nonlinear optic materials, bioactive compounds, drug cocrystal design, catalysis and photochemistry are also envisaged.

The self-assembly reaction of arylhydrazones of β-diketones (AHBD), namely 2-[2-(2,4-dioxopentan-3-ylidene)hydrazinyl]benzenesulfonic acid (H2L1) and 2-[2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl]benzenesulfonic acid (H2L2), with sodium or potassium hydroxides in MeOH/H2O (1/1, v/v) produces a series of coordination compounds, [Na3(μ3-HL1)2(μ4-HL1)(μ-H2O)(H2O)2]n (1), [Na2(HL1)2(μ-H2O)2(H2O)4]·4H2O (2), [Na(HL2)(μ-H2O)(H2O)2]n·nH2O (3), [K(μ4-HL1)(μ3-H2O)]n (4), and [K(μ4-HL2)(H2O)]n (5), which include the one-dimensional (3), two-dimensional (2D) (1, 4), and three-dimensional (3D) (5) coordination polymers, as well as the zero-dimensional dimer (2). Compounds 1–5 were isolated as air stable crystalline solids and characterized by IR, 1H, and 13C{1H} NMR spectroscopy, elemental, differential thermal, and single-crystal X-ray diffraction analysis. The latter shows that the monodeprotonated HL1– (L = L1, L2) anions act as multiple O-donors through the sulfonate and carbonyl groups and are also capa...

The methods of synthesis of arylhydrazones of methylene active compounds (AHMACs) as well as the preparation and properties of their metal complexes are reviewed. Nuclearity, supramolecular arrangements and other features (e.g., solubility, redox potentials, catalytic and antibacterial activities) of the complexes can be controlled by the introduction of different substituents to the methylene active and/or the aromatic fragments of AHMAC and by variation of metal-ions used in the synthesis.

New Cu II complexes [Cu(H 2 O)(μ-L 1 )Na(H 2 O)] n ·2 n H 2 O ( 4 ), [Cu(H 2 O)(μ-HL 2 )Na(H 2 O)] n ·2 n H 2 O ( 5 ) and [Cu(H 2 O)(μ-L 3 )Na(H 2 O)] n ·2 n H 2 O ( 6 ), bearing the SO 3 − or COO − -functionalized arylhydrazones of β-diketones (AHBDs) 3-(2-hydroxy-3-sulfo-5-nitrophenylhydrazone)pentane-2,4-dione (H 3 L 1 , 1 ), 3-(2-hydroxy-3,5-disulfophenylhydrazone)pentane-2,4-dione (H 4 L 2 , 2 ) or 1-ethoxy-2-(2-hydroxy-4-carboxyphenylhydrazone)butane-1,3-dione (H 3 L 3 , 3 ), were synthesized and characterized by elemental analysis, IR spectroscopy, ESI-MS and X-ray analysis (for 4 ). 4 – 6 were immobilized on the layered double hydroxides (LDH) [Zn 0.74 Al 0.26 (OH) 2 ]ǀ(NO 3 ) 0.26 ·0.23H 2 O and characterized by X-ray powder diffraction patterns (XRPD), UV–vis, IR spectroscopies, thermogravimetric (TG) and differential thermal (DTA) analyses. The heterogenized Cu II AHBD-LDH systems catalyze the peroxidative oxidation (with TBHP or H 2 O 2 as oxidant) of alkanes (cyclohexane, n -pentane, n -hexane, n -heptane, n -octane) mainly to alcohols, under mild conditions, and can be recycled at least five times without significant loss of activity, with overall yields of 10–15% per cycle depending on the catalyst used. Regioselectivity at position 2 of the alkane is favoured by the heterogenized catalysts.

New arylhydrazones of β-diketones, 2-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl) benzoic acid (1) and (Z)-ethyl-2-(2-(2-nitrophenyl)hydrazono)-3-oxobutanoate (2), have been synthesized by reaction of activated β-diketones with the corresponding aryldiazonium salts, and characterized by IR, 1H and 13C NMR spectroscopies and elemental analysis. In DMSO solution, 1 is stable exclusively in the hydrazone form, while 2 exists in DMSO and H2O solutions as a mixture of enol–azo and hydrazone tautomeric forms. In the latter case, an increase in the solvent polarity shifts the tautomeric balance to the enol–azo form. Solvatochromic, thermal and photoluminescent properties of 1, 2 and the known related 2-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)benzoic acid (3), (2-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)phenyl)arsonic acid (4), (Z)-2-(2-(1,3-dioxo-1-phenylbutan-2-ylidene)hydrazinyl)benzoic acid (5) and 5-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)-2,3-dihydrophthalazine-1,4-dione (6) were studied. The obtained UV–vis absorption spectra confirm that emах depends on the solvent and on the nature of AHBD, but no clear correlation was found. Upon heating, 1–3, 5 and 6 are stable up to 474 K and decompose in two steps whereas 4 decomposes in three steps starting from 343 K. The kinetic parameters of the thermal decomposition were estimated suggesting a low rate of the thermal decomposition. Compounds 2 and 3 exhibit luminescence with intense emission bands with maxima at λem of 466.0 (λex = 318 nm) and 532.5 nm (λex = 315 nm), respectively, while compounds 4 and 6 show low-intensity bands at λem of 501 (λex = 396 nm) and 503 nm (λex = 389 nm). Compounds 1 and 5 display no photoluminescence.

New arylhydrazones of β-diketones, 5-chloro-3-(2-(1-ethoxy-1,3-dioxobutan-2-ylidene)hydrazinyl)-2-hydroxybenzenesulfonic acid ( 1 ), 3-(2-(1-ethoxy-1,3-dioxobutan-2-ylidene)hydrazinyl)-2-hydroxy-5-nitrobenzenesulfonic acid ( 2 ), and 3-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene) hydrazinyl)-2-hydroxy-5-nitrobenzenesulfonic acid ( 3 ), have been synthesized and characterized by IR, 1 H and 13 C NMR spectroscopies and elemental analysis. 3 and known 5-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl)-4-hydroxybenzene-1,3-disulfonic acid ( 4 ) exist in DMSO solution exclusively in the hydrazone form, while 1 and 2 exist in DMSO and H 2 O solutions as a mixture of enol-azo and hydrazone tautomeric forms, in ratios dependent on the solvent polarity and inductive effect of the substituents. DFT and TDDFT approaches were applied for simulations of experimental UV–VIS absorption spectra of the studied compounds, taking into account solvatochromic as well as tautomeric effect. The performed simulations have established a correlation of substantial experimental 120 nm red shift of the enol-azo form with respect to hydrazone with HOMO and LUMO orbitals' delocalization.

Novel arylhydrazones of methylene active compounds – 3-(2-(1-ethoxy-1,3-dioxobutan-2-ylidene)hydrazinyl)-2-hydroxy-5-nitrobenzenesulfonic acid (1), 2-(2-(2-hydroxy-4-nitrophenyl)hydrazono)-2 H-indene-1,3-dione (2), 5-chloro-2-hydroxy-3-(2-(4,4,4-trifluoro-1,3-dioxo-1-(thiophen-2-yl)butan-2-ylidene)hydrazinyl) benzenesulfonic acid (3), 5-chloro-2-hydroxy-3-(2-(2,4,6-trioxo-tetrahydropyrimidin-5(6 H)-ylidene)-hydrazinyl)benzenesulfonic acid (4), 5-(2-(2-hydroxyphenyl)hydrazono)pyrimidine-2,4,6(1 H,3 H,5 H)-trione (5), 4-hydroxy-5-(2-(2,4,6-trioxo-tetrahydro-pyrimidin-5(6 H)-ylidene)hydrazinyl)benzene-1,3-disulfonic acid (6), 5-(2-(2-hydroxy-4-nitrophenyl)hydrazono)pyrimidine-2,4,6(1 H,3 H,5 H)-trione (7) and 5-chloro-3-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl)-2-hydroxybenzenesulfonic acid (8) have been synthesized by a reaction between the corresponding methylene active compounds and aryldiazonium salts, and characterized by IR, 1 H and 13 C NMR spectroscopies and element analysis. The collected information confirms that 2, and 4 – 8 exist in DMSO solution in hydrazone form, being stabilized by an intramolecular hydrogen bond, while 1 and 3 exist in mixed enol-azo and hydrazo tautomeric forms. The antimicrobial activity of 1 – 8, as well as that of known analogs 5-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl)-4-hydroxybenzene-1,3-disulfonic acid (9), 2-(2-sulfophenylhydrazo)malononitrile (10), 2-(2-carboxyphenylhydrazo) malononitrile (11), 2-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)phenylarsonic acid (12) and 5-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)-2,3-dihydrophthalazine-1,4-dione (13), have been studied. It was found that arylhydrazones of barbituric acid are more active than other methylene active compounds. A whole-cell bacterial luminescence biosensor method was used to detect the antimicrobial activity of the synthesized compounds. The results show that compounds 5 and 9 effectively inhibit the luminescence of Staphylococcus aureus at a minimum inhibitory concentration (MIC50) of 10 and 9 μg/ml, respectively. For Staphylococcus epidermidis, compound 11 showed the most potent activity with MIC50 of 17 μg/mL; for Pseudomonas aeruginosa, compounds 11 showed the most potent activity at MIC50 of 10 μg/mL. Observed results have been verified to be statistically significant using the two-tailed test.

New arylhydrazone derivatives of β-diketones, 2-(4-bromophenylhydrazono)-5,5-dimethylcyclohexane-1,3-dione ( 1 ), 5-(4-bromophenylhydrazono)pyrimidine-2,4,6(1 H ,3 H ,5 H )-trione ( 2 ) and ( E )-2-(4-bromophenylhydrazono)-1-phenylbutane-1,3-dione ( 3 ), were prepared by coupling of β-diketone with the respective para -bromophenyldiazonium chloride, and characterized by IR, 1 H and 13 C NMR spectra. The IR and NMR spectral data disclose an effective intramolecular hydrogen bonding in all the cases. The single crystal X-ray analysis of 3-(4-bromophenyl-hydrazono)pentane-2,4-dione ( 4 ) evidences the intramolecular resonance-assisted hydrogen bonding (RAHB) which is significantly strengthened in view of the planarity of the six atoms involved in the resonance cycle. Compound 3 derived from the unsymmetric 1-phenylbutane-1,3-dione exists in solution as a mixture of the enol-azo and hydrazone tautomeric forms and an increase of the solvent polarity shifts the tautomeric balance to the enol-azo form, while for 1 , 2 and 4 , derived from the symmetric β-diketones, the hydrazone form is dominating under all the studied conditions.

New 3D Cu(II)-K coordination polymers (CPs), [CuK(μ7-L1)(H2O)]n·nH2O (1), and [CuK(μ5-L2)(H2O)]n·2nH2O (2), were easily generated by self-assembly from copper(II) nitrate, potassium hydroxide, and azo derivatives of β-diketones, namely 3-(2-hydroxy-3-sulfo-5-chlorophenylhydrazo)pentane-2,4-dione (H3L1) or 3-(2-hydroxy-3-sulfo-5-nitrophenylhydrazo)pentane-2,4-dione (H3L2). The single-crystal structures of 1 and 2 disclose similar 3D metal–organic networks, driven by the 5-connected potassium, 6-connected L1, or 5-connected L2 nodes. The topological analysis of 1 reveals a rare binodal 5,6-connected underlying net with an unprecedented topology defined by the point (Schlafli) symbol of (3·45·53·6)(32·46·53·64), while 2 features a uninodal 5-connected net with the bnn (hexagonal boron nitride) topology and the point symbol of (46·64). Both networks possess voids filled by crystallization water molecules, the reversible escape and binding of which was studied by thermal analyses. Upon a dehydration–adsorption...

A new water-soluble β-diketone azo derivative ― 3-(5-chloro-2-hydroxy-3-sulfophenylhydrazo)pentane-2,4-dione(H3L, 1) ― was synthesized and found to be stable in DMSO solution and in the solid state in the hydrazo tautomeric form. Its water-soluble complexes [Co(HL)(en)(H2O)]·4H2O (3) and the zwitterionic [Cu(L)(Hen)(H2O)] (4), with buffering properties, were prepared by reaction of cobalt(II) and copper(II) nitrates with the ethylenediammonium (H2en) salt of 1, (H2en)(HL) (2). In the formation of 3 and 4, 1 is a chelating ligand, and a crucial synthetic and structural role is played by en, allowing the organization of water-soluble assemblies and influencing the overall 3D supramolecular arrangement. Compound 3 is the first cobalt complex with an azo derivative of a β-diketone. Complex 4 acts as catalyst precursor for the aerobic TEMPO-mediated selective oxidation of benzylic alcohols to the corresponding aldehydes in aqueous media.

(E)-2-(2-(2-hydroxyphenyl)hydrazono)-1-phenylbutane-1,3-dione (H2L) was synthesized by azocoupling of diazonium salt of 2-hydroxyaniline with 1-phenylbutane-1,3-dione and characterized by IR, 1H and 13C NMR spectroscopies and X-ray diffraction analysis. In solution, H2L exists as a mixture of the enol-azo and hydrazone tautomeric forms and a decrease of temperature and of solvent polarity shifts the tautomeric balance to the hydrazone form. In the solid state, H2L crystallizes from ethanol–water in the monohydrate hydrazone form, as shown by X-ray analysis. The dissociation constants of H2L (pK1 = 5.98 ± 0.04, pK2 = 9.72 ± 0.03) and the stability constants of its copper(II) complex (log β1 = 11.01 ± 0.07, log β2 = 20.19 ± 0.08) were determined by the potentiometric method in aqueous-ethanol solution. The copper(II) complex [Cu2(μ-L)2]n was isolated in the solid state and found by X-rays to be a coordination polymer of a binuclear core with a distorted square pyramidal metal coordination geometry.

The structural, tautomeric and acid–base properties of the new 1-phenyl-2-(2-hydroxy-3-sulfo-5-chlorophenylhydrazo)butane-1,3-dione (H2L1), 1-phenyl-2-(2-hydroxy-3,5-disulfophenylhydrazo)butane-1,3-dione (H2L2), 1-phenyl-2-(2-hydroxy-3-sulfo-5-nitrophenylhydrazo)butane-1,3-dione (H2L3) and 1-phenyl-2-(2-hydroxy-4-nitrophenylhydrazo)butane-1,3-dione (H2L4) were studied using IR, 1H and 13C NMR spectroscopies and potentiometry. The study reveals that H2L1–4 and the known 1-phenyl-2-(2-hydroxyphenylhydrazo)butane-1,3-dione (H2L5) exist in solution as a mixture of Z-enol-azo-II and hydrazo-III tautomeric forms and that an increase in the solvent polarity shifts the tautomeric balance to the enol-azo form. The thermodynamic parameters of the proton dissociation in H2L1–5 were determined showing that this process is unspontaneous, endothermic and entropically unfavorable.

The methods of synthesis of 1,3,5-triazapentadienes (also known as imidoylamidines), as well as the preparation of their complexes, are reviewed. The former methods include mainly the Pinner, Ley and Muller syntheses, the amination of N-imidoylimidoates or of nitriles bearing strong electron-withdrawing groups, the desulfurizing amination of N-tiobenzoylbenzamidines and the reaction of perfluoro-5-aza-4-nonene with primary amines. The synthetic procedures for the complexes involve not only the coordination of a pre-formed 1,3,5-triazapentadiene but also the generation in situ of such a species, namely by condensation of amidines, by direct one-pot template synthesis from nitriles, by nucleophilic addition of amidines or related reagents to coordinated nitriles, by nucleophilic additions to dicyanamidate or hydrolytic conversion of triazines.

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.

The previously unknown reactions between phthalonitriles, 1,2-(CN)2(C6)R1R2R3R41 (1 a, R1=R2=R3=R4=H; 1 b, R1=R2=R4=H, R3=CH3; 1 c, R1=R4=H, R2=R3=Cl; 1 d, R1=R2=R3=R4=Cl; 1 e, R1=R2=R3=R4=F), and a cyclic nitrone, −O+NCHCH2CH2CMe22, proceed under heating in a sealed tube to give phthalimides 3, 2-oxadiazolyl-benzonitriles 4 or ortho-bis(oxadiazolyl)tetrafluorobenzene 4 e′. In the presence of palladium(II) chloride, phthalonitriles 1 react with 2 at room temperature, to give bis(pyrrolidin-2-ylidene)phthalamide PdII complexes 5 via metal-promoted rupture of the NO bond of the oxadiazoline ring. The ketoimine ligands thus generated can be liberated from the metal by displacement with a diphosphine. Although the first [2+3] cycloaddition of 2 to 1 can occur in the absence of the metal to give the mono-cycloadducts 4, the second [2+3] coupling at the still-unreacted cyano group requires its activation by coordination to PdII, affording complexes 6 containing two ligated oxadiazolyl-benzonitriles. These ligands undergo either i) further cycloaddition with 2 to afford ultimately (upon rearrangement) the bis(pyrrolidinylidene)phthalamide complexes 5 or ii) NO bond cleavage in the oxadiazoline ring with intramolecular attack of the imine nitrogen on the cyano carbon and bridging to a second PdII center to afford dimeric palladium(II) complexes 7, with chloride bridges, that bear a dihydropyrrolyl-iminoisoindolinone, a new type of ligand. The compounds were characterized by IR, 1H, and 13C NMR spectroscopy, ESI MS or FAB+ MS, elemental analyses and, in the case of 4 c, 5 a, 5 c, and 7 c, also by X-ray diffraction analysis. Complexes 5 a and 7 c show high catalytic activity for the Suzuki–Miyaura cross-coupling reaction of bromobenzene and phenylboronic acid and give biphenyl in high yields with turnover frequencies (TOFs) of up to 9.0×105 h−1.

Refluxing a mixture of phthalonitrile C 6 R 1 R 2 R 3 R 4 (CN) 2 1 (R 1 -R 4 =H), or its substituted derivatives 2 (R 1 , R 3 , R 4 =H, R 2 =Me), or 3 (R 1 , R 4 =H, R 2 , R 3 =Cl) (1 equiv.) and N,N-diethylhydroxylamine, Et 2 NOH, (4 equivs.) in methanol for 4 h results (Route A) in precipitation of the symmetrical (6 and 8) and an isomeric mixture of unsymmetrical (7) phthalocyanines, isolated in good (55-65 %) yields. The reaction of phthalonitriles 1, 2, or 4 (R 1 , R 3 , R 4 =H, R 2 =NO 2 ) (4 equivs.) with Et 2 NOH (8 equivs.) in the presence of a metal salt MCl 2 (M= Zn, Cd, Co, Ni) (1 equiv.) in n-BuOH or without solvent results in the formation of metallated phthalocyanine species (9-17). Upon refluxing in freshly distilled dry chloroform, phthalonitrile 1 or its substituted analogues 2, 3 or 5 (R 1 -R 4 =F) (1 equiv.) react with N,N-diethylhydroxylamine (2 equivs.) affording 3-iminoisoindolin-1-ones 18-21 (Route B) isolated in good yields (55-80%). All the prepared compounds were characterized with C, H, and N elemental analyses, ESI-MS, IR, and compounds 18-21 also by ID ( 1 H, 13 C{1H}), and 2D ( 1 H, 15 N-HMBC and 1 H, 13 C-HMQC, 1 H, 13 C-HMBC) NMR spectroscopy.

Thiazole derived compounds have great potential in medicinal- and agro-chemistries, catalysis, cosmetic industry, corrosion protection, light harvesting, production of light-emitting diodes (LEDs), photochromes and molecular switches or nonlinear optical materials. In spite of that, not much attention has been paid to the coordination chemistry of this class of versatile and polyfunctional heterocyclic ligands. This review intends to systematize the existing information in this field and to highlight some perspectives in the synthesis and applications of 1,3-thiazole, isothiazole and thiadiazole metal complexes.

The new copper(II) or copper(II)/sodium(I) 1D coordination polymers [Cu2(Hmdea)2(mu-H2O)(mu2-tpa)]n.2nH2O (1), [Cu2(H2tipa)2(mu2-ipa)]n.4nH2O (2), [Cu2(H2tea)2Na(H2O)2(mu2-tma)]n.6nH2O (3), [Cu2(H2tea)2(mu2-ipa)]n.nH2O (4a), and [Cu2(H2tea)2{mu3-Na(H2O)3}(mu3-ipa)]n(NO3)n.0.5nH2O (4b) have been prepared in aqueous medium by self-assembly from copper(II) nitrate, aminopolyalcohols [methyldiethanolamine (H2mdea), triisopropanolamine (H3tipa), and triethanolamine (H3tea)] as main chelating ligands and benzenepolycarboxylic acids [terephthalic (H2tpa), isophthalic (H2ipa), and trimesic (H3tma) acid] as spacers. They have been characterized by IR spectroscopy, elemental and single-crystal X-ray diffraction analyses, the latter indicating the formation of unusual multinuclear metal cores interconnected by various benzenepolycarboxylate spacers, leading to distinct wavelike, zigzag, or linear 1D polymeric metal-organic chains. These are further extended to 2D or 3D hydrogen-bonded supramolecular networks via extensive interactions with the intercalated crystallization water molecules. The latter are associated, also with aqua ligands, by hydrogen bonds resulting in acyclic (H2O)3 clusters in 1, (H2O)8 clusters in 2, infinite 1D water chains in 3, and disordered water-nitrate associates in 4b, all playing a key role in the structure stabilization and its extension to further dimensions. Variable-temperature magnetic susceptibility measurements have shown that 1-4 exhibit a moderately strong ferromagnetic coupling through the alkoxo bridge. The small Cu-O-Cu bridging angle and the large out-of-plane displacement of the carbon atom of the alkoxo group accounts for this behavior. The magnetic data have been analyzed by means of a dinuclear and a 1D chain model, and the magnetic parameters have been determined. The magnetic exchange coupling in 3, to our knowledge, is the highest found in alkoxo-bridged copper(II) complexes.

The coupling between coordinated propiononitriles in trans-[PtCln(EtCN)2] (n = 2, 4) and the 1,2-hydroxylaminooximes HON(H)CMe2C(R)=NOH (R = Ph 1, Me 2) proceeds smoothly in CHCl(3) at ca. 40-45 degrees C and gives trans-[PtCln{NH=C(Et)ON(H)CMe2C(R)=NOH}2] (n = 2, R = Ph 5, Me 6; n = 4, R = Ph 7, Me 8) in 80-85% isolated yields. The reaction is highly regioselective, and both spectroscopic (IR; FAB+-MS; 1D 1H, 13C{1H}, and 195Pt NMR; and 2D 1H,13C HMQC, 1H,13C HMBC, and 1H,15N HMQC NMR) and X-ray data for 6-8 suggest that the addition proceeds exclusively via the hydroxylamine moiety of the 1,2-hydroxylaminooxime species; the existence of an oxime group remote from the nucleophile was also confirmed. Heating of 6 in air leads to its conversion to the unusual nitrosoalkane complex [PtCl2{HON=C(Me)C(Me)2N=O}] (9), whereas in the case of 5, only the metal-free salt [H3NC(Me)2C(Ph)=NOH]2(NO3)Cl.H2O (10) was isolated. To compare the kinetic aspects and trends in the addition of both types of nucleophiles (oximes and hydroxylamines; for the latter, see our recent work: Inorg. Chem. 2005, 44, 2944) to coordinated nitriles, a kinetic study of the addition of HON=C(CH2Ph)2 to [Ph3PCH2Ph][PtCl5(EtCN)] (11) to give [Ph(3)PCH(2)Ph][PtCl(5){NH=C(Et)ON=C(CH2Ph)2}] (12) was performed. The calculated rate constant k2 of 3.9 x 10(-6) M(-1) s(-1) at -20 degrees C for the addition of the oxime indicates that the hydroxylamine is, by a factor 1.7 x 10(4), more reactive toward the addition to nitriles than the oxime. Results of the synthetic, kinetic, and theoretical (at the B3LYP level of theory) studies have demonstrated that the high regioselectivity of the reactions of the 1,2-hydroxylaminooximes with ligated nitriles is both kinetically and thermodynamically controlled.

A new aqua-soluble CuII-Na coordination polymer, {[Cu(H2O)Na(H2O)(η9-L)]·2H2O}n, was easily generated by self-assembly from copper(II) nitrate, sodium hydroxide and 2-hydroxy-5-nitro-3-(2-(2,4,6-trioxotetrahydropyrimidin-5(2H)-ylidene)hydrazinyl)benzene sulfonic acid (H3L) a new hydrosoluble arylhydrazone of barbituric acid. The complex was characterized by IR spectroscopy, elemental and single‐crystal X-ray diffraction analyses, which disclosed 1D metal-organic chains driven by the intricate nona-chelation of the fully deprotonated L3− derivative to five metal cations (three NaI and two CuII). These chains have intercalated crystallization water molecules enabling the expansion of the structure to 3D by means of extensive hydrogen bond interactions.

In spite of its impressive record in medicinal chemistry, the role of barbituric acid H 3 BA (pyrimidine-2,4,6(1 H ,3 H ,5 H )-trione) in coordination, organometallic and supramolecular chemistries has not yet been analyzed and reviewed. However, H 3 BA can be readily functionalized and provides rich opportunities to create coordination bonds and non-covalent interactions. Thus, derivatives of H 3 BA (barbituric acids, BAs) are widely used for the preparation of a wide range of complexes with various metals of almost all groups of the periodic table. The review systematizes information on the synthesis, tautomerism, acid–base properties of BAs and their use for the construction of organometallic and coordination compounds, as well as coordination polymers and supramolecular assemblies. The role of different metal ions and the structure of BAs in directing the preparative pathways and tuning particular structural properties of the resulting compounds are discussed. Some valuable applications of BAs, in particular in the construction of molecular receptors, magnetic and nonlinear optic materials, bioactive compounds, drug cocrystal design, catalysis and photochemistry are also envisaged.

One-pot template condensation of CCl3CN with ammonia on a metal source [MnCl2·4H2O, FeCl3·6H2O or Co(CH3COO)2·4H2O] in DMSO led to the formation of tris{2,4-bis(trichloromethyl)-1,3,5-triazapentadienato}-M(III) complexes, [M{NHC(CCl3)NC(CCl3)NH}3]·n(CH3)2SO [M = Mn, n = 1 (1); M = Fe, n = 2 (2); M = Co, n = 2 (3)], which were characterized using elemental analysis, and IR, ESI-MS and single-crystal X-ray analysis. The role of inter- and intramolecular non-covalent halogen and hydrogen bonds in the synthesis of 1–3 is discussed. It is shown that the crystal ionic radii of the metal ions [68.5 (Co) 3.155 (2) > 3.133 (1) A]. Compounds 1–3 and the related di(triazapentadienato)-Cu(II) complex [Cu{NHC(CCl3)NC(CCl3)NH}2]·2(CH3)2SO (4) act as catalyst precursors for the additive-free microwave (MW) assisted homogeneous oxidation of 1-phenylethanol with tert-butylhydroperoxide (TBHP), leading to the formation of acetophenone with yields up to 99% and TONs up to 5.0 × 103 after 1 h of low power (10 W) MW irradiation.

The aquasoluble Fe(III) complexes [Fe(H(2)O)(3)(L(1))]∙4H(2)O (3) and [Fe(H(2)O)(3)(L(2))]∙3H(2)O (4), bearing the basic forms of 5-chloro-3-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl)-2-hydroxy-benzenesulfonic acid (H(3)L(1), 1) and 3-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)-2-hydroxy-5-nitrobenzenesulfonic acid (H(3)L(2), 2), were synthesized and fully characterized including by X-ray crystal structural analysis. In the channels of the water-soluble 3D networks of 3 and 4, the uncoordinated water molecules are held by oxygen atoms of the carbonyl and sulfonyl groups, and by the water ligands. The Fe(III) coordination environment resembles that in the active sites of some mononuclear non-heme iron-containing enzymes. The complexes show a high catalytic activity for the peroxidative oxidation (with aqueous H(2)O(2)) of C(5)-C(8) cycloalkanes to the corresponding alcohols and ketones under mild conditions. The effects of various factors, such as amounts of oxidant, catalyst and HNO(3) additive, were investigated allowing to reach overall yields of ca. 25% and turnover numbers (TONs) up to 290. The catalytic reactions proceed via both oxygen- and carbon-radicals as shown by radical trap experiments.

The DFT modeling of novel synthesized azoderivatives of β-diketones - 2-(2-(2-hydroxyphenyl)hydrazono)-1,3-diphenylpropane-1,3-dione (1), 2-(2-(2-hydroxy-4-nitrophenyl)hydrazono)-1,3-diphenylpropane-1,3-dione (2), 3-(2-(1,3-dioxo-1,3-diphenylpropan-2-ylidene)hydrazinyl)-2-hydroxy-5-nitrobenzene sulfonic acid (3), 2-(2-(1,3-dioxo-1,3-diphenylpropan-2-ylidene)hydrazinyl)benzenesulfonic acid (4), 2-(2-(1,3-dioxo-1,3-diphenylpropan -2-ylidene)hydrazinyl)benzoic acid (5), 2-(2-(2-hydroxy-4-nitrophenyl)hydrazono)-1-phenylbutane-1,3-dione (6) were performed. The collected information confirms that 1-5 exist in hydrazo form, being stabilized by the intramolecular hydrogen bonds in DMSO solution and solid phase, while 6 exists in mixed enol-azo and hydrazo tautomeric forms, the latter dominating in more polar solvents. The relative stability of various tautomeric and izomeric forms of the symmetric 1-5 and unsymmetric 6 azoderivatives of β-diketones is calculated based on the density functional theory (DFT). Polarizable Continuum Model was used to simulate solvatochromic effects. Solvents of different polarities were used to collect experimental spectra, and the same solvents were chosen for the PCM calculations. The optical properties of 1-6 have been investigated by density functional theory and its electronic absorption bands have been assigned by time-dependent density functional theory (TD-DFT).

[2 + 3] Cycloaddition reactions of the organonitriles RCN 1 (R = Me (1a), Et (1b), p-IC(6)H(4) (1c), p-BrC(6)H(4) (1d), p-ClC(6)H(4) (), p-FC(6)H(4) (1e)) with the pyrroline N-oxide (-)O(+)[upper bond 1 start]N[double bond, length as m-dash]CHCH(2)CH(2)C[upper bond 1 end]Me(2) in the presence of PdCl(2) proceed at room temperature for 12 h and allow the isolation of the corresponding palladium(ii) complexes trans-[PdCl(2){[upper bond 1 start]N[double bond, length as m-dash]C(R)O[lower bond 1 start]NC[upper bond 1 end](H)CH(2)CH(2)C[lower bond 1 end]Me(2)}(2)] 3a-3f containing fused bicyclic Delta(4)-1,2,4-oxadiazoline ligands, in good to excellent yields (75-90%). Treatment of trans-[PdCl(2)(EtCN)(2)] with the nitrone in acetone or propionitrile at room temperature affords, in good yield, (R = Et), confirming that complexes 3 are formed via nitrile activation by coordination. These reactions proceed with high diastereoselectivity and afford mixtures of enantiomers, due to the rigid conformation (E) of the cyclic nitrone 2. The oxadiazolines [upper bond 1 start]N[double bond, length as m-dash]C(R)O[lower bond 1 start]NC[upper bond 1 end](H)CH(2)CH(2)C[lower bond 1 end]Me(2) (R = Et (4b), p-FC(6)H(4) (4f)) are liberated upon reaction of complexes 3b,3f with a diphosphine (dppe). During the liberation of , the complex trans-[PdCl(2){[upper bond 1 start]N[double bond, length as m-dash]C(NHCOC(6)H(4)F-4)CH(2)CH(2)C[upper bond 1 end]Me(2)}(2)] was formed in a minor amount upon N-O bond cleavage of the oxadiazoline ring to give a pyrrolylbenzamide species coordinated by the N-atom of the pyrrolyl moiety. The compounds were characterized by IR, (1)H and (13)C NMR spectroscopies, ESI-MS, elemental analyses and, in the cases of 3b, 3d and 5, also by X-ray diffraction analyses. Complexes 3b and 3f show a high catalytic activity towards the microwave-assisted Suzuki-Miyaura cross-coupling reaction in aqueous medium, achieving a TON value of 2.7 x 10(5) and a TOF value of 1.1 x 10(6) h(-1).

Treatment of alkyl nitriles with NiX(2).6H(2)O (X = Cl, NO(3)) and 2-propanone oxime, followed by (X = Cl) addition of [i-Pr(4)N](NO(3)) for precipitation of the product, resulted in the formation of amidinium nitrates [RC([double bond]NH(2))NH(2)](NO(3)) (R = Me, Et, n-Pr). The reaction went to another direction with NiX(2).2H(2)O, i.e., the reaction between neat RCN (R = Me, Et, n-Pr, i-Pr, n-Bu, CH(2)Cl, CH(2)C(6)H(4)OMe-p) and NiCl(2).2H(2)O/2-propanone oxime (other ketoximes can also be used) gave the (imidoylamidine)Ni(II) complexes [Ni[N(H)[double bond]C(R)NHC(R)[double bond]NH](2)](2+) (1(2+)-7(2+)). The latter were isolated in good yields (65-91%) as the bis-chloride salts 1.Cl(2)-6.Cl(2) and the mixed salt 7.(Cl)(p-MeOC(6)H(4)CH(2)CO(2)). Remarkably, the latter transformation does not proceed at all if NiCl(2).2H(2)O or the ketoxime are taken alone. Liberation of imidoylamidines was performed for one alkyl-containing complex [2.Cl(2)] and one benzyl-containing complex [7.(Cl)(p-MeOC(6)H(4)CH(2)CO(2))], by (i) addition of HBF(4).Et(2)O to the acetonitrile solution of the complexes to yield [N(H)[double bond]C(R)NHC(R)[double bond]NH].2HBF(4) (R = Et 8 and R = CH(2)C(6)H(4)OMe-p 9) or (ii) substitution for ethanediamine (en) with following precipitation of the complex [Ni(en)(3)]Cl(2) with formation of free N(H)[double bond]C(R)NHC(R)[double bond]NH (R = Et 10 and R = CH(2)C(6)H(4)OMe-p 11). In contrast to the liberation in nonaqueous media, treatment of 2.Cl(2) and 7.(Cl)(p-MeOC(6)H(4)CH(2)CO(2)) with Na(2)EDTA.2H(2)O in water-methanol solutions led to substitution and hydrolysis to furnish the acyl amides [EtC([double bond]O)](2)NH (12) and [p-MeOC(6)H(4)CH(2)C([double bond]O)](2)NH (13). Alternatively, 12 and 13 were obtained by hydrolysis of 10 and 11 in water at pH ca. 8.5. It was shown that the oxime complexes trans-[NiCl(2)(C(4)H(8)C[double bond]NOH)(4)] (14) or cis-[Ni(O,O-NO(3))(2)(C(4)H(8)C[double bond]NOH)(2)] (15) can be intermediates in the formation of amidines and imidoylamidines. The sequence of the Ni(II)/oxime mediated formation of (imidoylamidine)Ni complexes and liberation (or hydrolytic liberation) of the ligands opens up a novel, facile and environmentally benign route to imidoylamidines and acyl amides.

Phthalonitrile, acetoxime and cobalt(II) nitrate hexahydrate are combined in acetone with formation of stable and easy to handle Co(II) complex [Co{C6H4C(NH2)NC(ONCMe2)2}2](NO3)2 (1). Interaction of 1 with excess alcohols ROH (also used as solvents) and 2 equiv of (NH4)2S leads, in one-step, to alkyl 2-carbamimidoylbenzoate nitrates [C6H4COOR{2-C(NH2)2}]NO3 [R=CH3, C2H5, C3H7, CH(CH3)2]. Similarly, N1,N3-dialkyl-1H-isoindole-1,3-diaminate nitrates [C6H4C(NR′)NC(NR′)]NO3 [R=C3H7, C4H9, C(CH3)3, CH2CH2OH, CH2CH2SC2H5) can be directly produced from 1 by its reaction with 4 equiv of amines and 2 equiv of (NH4)2S in alcoholic media.

The hydrolysis of sterically hindered and unhindered alkyl nitriles, and also of benzyl and phenyl nitriles RCN (R = Me, CH(2)Cl, Et, n-Pr, i-Pr, n-Bu, t-Bu, p-MeOC(6)H(4)CH(2), Ph), to carboxamides is catalyzed by a novel system of superior simplicity consisting of cheap, widely commercially available, and rather environmentally friendly compounds, that is, a ZnX(2)/ketoxime combination, but it does not proceed at all with either the zinc salt or the ketoxime taken alone. The nature of the anion X(-) in the zinc salt (X = NO(3), Cl, CF(3)SO(3)) or of the ketoxime (Me(2)C=NOH, C(4)H(8)C=NOH, C(5)H(10)C=NOH) does not affect strongly the catalytic properties of the system, but the best results were obtained so far with a Zn(NO(3))(2).6H(2)O/2-propanone oxime molar ratio of 1:4; turnover numbers are typically above ca. 100 but reach as high as 1000 for p-MeOC(6)H(4)CH(2)C(=O)NH(2). The previously unknown structures of the two carboxamide products n-BuC(=O)NH(2) and p-MeOC(6)H(4)CH(2)C(=O)NH(2) were determined by X-ray diffraction studies. The complexes [ZnX(2)(R(2)C=NOH)(2)] (X = Cl, R(2) = 2Me, C(4)H(8), C(5)H(10); X = NO(3), R = C(4)H(8)), prepared by heating the appropriate zinc salts with 2 equiv of the ketoxime in acetone and characterized by C, H, N analyses, FAB-MS, (1)H and (13)C[(1)H] NMR spectroscopies, and also X-ray crystallography (for X = Cl, R(2) = 2Me; X = NO(3), R = C(4)H(8)), proved to be catalyst precursors in the conversions because the activity of these species is high only in the presence of 2 equiv of the ketoxime.

A water-soluble iron(III) complex [Fe(H2O)3(L)]·5H2O (1) was prepared by reaction of iron(III) chloride with 5-chloro-3-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl)-2-hydroxy-benzenesulfonic acid (H3L). The complex was characterized by IR, 1H NMR and ESI-MS spectroscopies, elemental and X-ray crystal structural analyses. The coordination environment of the central iron(III) is a distorted octahedron, three sites being occupied by L3− ligand, which chelates in O,N,O fashion, while three other sites are filled with the water molecules. The uncoordinated water molecules are held in the channels of the overall 3D supramolecular structure by the carbonyl and sulfonyl groups of L3− and the ligated waters. Apart from the multiple hydrogen bonds, an intermolecular charge-assisted O···Cl halogen bonding with 3.044 A distance was described. 1 acts as an effective catalyst in the Henry reaction producing nitroaldols from nitroethane and various aldehydes with yields up to 90% and threo/erythro diastereoselectivity ranging from 3:1 to 1:1.

The aquasoluble [Cu(H2O)((CH3)2NCHO)(HL)] (2) and [Cu2(CH3OH)2(μ-HL)2] (3) CuII complexes were prepared by reaction of CuII nitrate hydrate with the new 3-(2-hydroxy-4-carboxyphenylhydrazone)pentane-2,4-dione (H3L, 1), in the presence (for 2) or absence (for 3) of (n-C4H9)2SnO, and characterized by elemental analysis, IR spectroscopy and X-ray single crystal diffraction. Magnetic susceptibility measurements, in compound 3, reveal strong antiferromagnetic coupling between the CuII ions through the μ2-phenoxido-O atoms, J = −203(1) cm−1. Complexes 2 and 3 act as catalyst precursors for the acid-free peroxidative oxidation of cyclohexane to the mixture of cyclohexyl hydroperoxide (primary product), cyclohexanol and cyclohexanone (TONs and yields up to 163 and 14.4%, respectively), as well as for the selective aerobic oxidation of benzyl alcohols to benzaldehydes in aqueous solution, mediated by a TEMPO radical, under mild conditions (TONs and yields up to 390 and 94%, respectively). In the alkane oxidations, 2 and 3 appear to behave as “dual role catalysts” combining, in one molecule, an active metal centre and an acidic promoting group, to provide a high activity of the system even without any acid promoter.

The zinc(II) complexes with ortho-hydroxy substituted arylhydrazo-β-diketonates [Zn(2)(CH(3)OH)(2)(μ-L(1))(2)] (5), [Zn{(CH(3))(2)SO}(H(2)O)(L(2))] (6), [Zn(2)(H(2)O)(2)(μ-L(3))(2)] (7) and [Zn(H(2)O)(2)(L(4))]·H(2)O (8) were synthesized by reaction of a zinc(II) salt with the appropriate hydrazo-β-diketone, HO-2-C(6)H(4)-NHN=C{C(=O)CH(3)}(2) (H(2)L(1), 1), HO-2-O(2)N-4-C(6)H(3)-NHN=C{C(=O)CH(3)}(2) (H(2)L(2), 2), HO-2-C(6)H(4)-NHN=CC(=O)CH(2)C(CH(3))(2)CH(2)C(=O) (H(2)L(3), 3) or HO-2-O(2)N-4-C(6)H(3)-NHN=[CC(=O)CH(2)C(CH(3))(2)CH(2)C(=O) (H(2)L(4), 4). They were fully characterized, namely by X-ray diffraction analysis that disclosed the formation of extensive H-bonds leading to 1D chains (5 and 6), 2D layers (7) or 3D networks (8). The thermodynamic parameters of the Zn(II) reaction with H(2)L(2) in solution, as well as of the thermal decomposition of 1-8 were determined. Complexes 5-8 act as diastereoselective catalysts for the nitroaldol (Henry) reaction. The threo/erythro diastereoselectivity of the β-nitroalkanol products ranges from 8:1 to 1:10 with typical yields of 80-99%, depending on the catalyst and substrate used.

The copper(II)-mediated integration between various 3-iminoisoindolin-1-ones and neat organonitriles (which play a dual role of solvent and reactant), under heating for ca. 12 h, and without requiring any base, accomplishes the release of the solid (1,3,5-triazapentadienato)Cu(II) complexes [Cu{HN=C(R)N=C(C(6)R(1)R(2)R(3)R(4)CO)N}(2)] (1-11) bearing the incorporated iminoisoindolin-1-one fragment. These compounds were isolated in moderate to good yields (44-78%) and do not require further purification. The iminoisoindolinone-nitrile coupling is Cu(II)-mediated and has a general character insofar as it can be efficiently applied for both unsubstituted (R(1)-R(4) = H) and substituted iminoisoindolin-1-ones (R(1), R(3), R(4) = H, R(2) = Me; R(1), R(4) = H, R(2), R(3) = Cl; R(1)-R(4) = F), and a wide range of nitriles (R = Me, Et, Pr(n), Pr(i), C(6)H(11), CH(2)Ph). Complexes 1-11 were characterized by elemental analyses (C, H, N), FAB(+)-MS, IR spectroscopy, and additionally compounds 1, 2 and 4 by single-crystal X-ray diffraction.