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A theoretical study of the reactivity of pyrazaboles with amines and pyrazoles has been carried out at DFT level in gas phase, toluene and water media. The reaction with amines yields two molecules of pyrazolylboranes, while the reaction with pyrazoles allows to understand the interchange of such molecules in the pyrazaboles. The reaction of three pyrazaboles with two amines [N[H.sub.3] and NM[e.sub.3]] and pyrazole itself has been considered. The [S.sub.N]2 and [S.sub.N]1 mechanisms have been analyzed. The [S.sub.N]2 reaction is more favorable than the [S.sub.N]1 in the absence or presence of amines. Keywords: pyrazaboles, pyrazolylboranes, [S.sub.N]2, [S.sub.N]1, dative bonds Nous avons realise une etude theorique de la reactivite des pyrazaboles avec les amines et les pyrazoles au niveau de la theorie de la fonctionnelle de la densite (DFT) en phase gazeuse, dans le toluene et en milieu aqueux. La reaction avec les amines mene a la formation de deux molecules de pyrazolylboranes, tandis que la reaction avec les pyrazoles permet de comprendre l'echange de ces molecules dans les pyrazaboles. Nous avons examine la reaction de trois pyrazaboles avec deux amines [N[H.sub.3] et NM[e.sub.3]] et le pyrazole comme tel. Nous avons analyse les mecanismes [S.sub.N]2 et [S.sub.N]1. La reaction [S.sub.N]2 est plus favorable que la reaction [S.sub.N]1, en l'absence comme en presence d'amines. [Traduit par la Redaction] Mots-cles : pyrazaboles, pyrazolylboranes, [S.sub.N]2, [S.sub.N]1, liaisons bipolaires, 1. Introduction At the intersection of the fields of boron, heterocyclic, and coordination chemistry, there are two topics, both discovered by Trofimenko in the 1966-1967, which have been a success [...]

An efficient approach for the synthesis of N-acetyl- and N-aroyl-2-pyrazlines by intramolecular Michael addition of [alpha],[beta]-unsaturated hydrazones is reported. The strategy can be applied to obtain substituted azaproline derivatives in a diastereoselective route.

The synthesis and characterization of emissive complexes involving the Pt(II) metal element displaying blue phosphorescence with fair color chromaticity are described. The blue-emitting Pt(II) complexes are prepared by the treatment of a pyridylpyrazole chelate 3-(trifluoromethyl)-5-(2-pyridyl)pyrazole (fppzH) with [K.sub.2]Pt[Cl.sub.4] in aqueous HCl solution.

The structural, spectroscopic, electrochemical and magnetic properties of pyrazolate and caboxylate complexes [[Fe.sub.3]([[mu].sub.3]-O)[([mu]-LL).sub.6][L.sub.3] containing the [Fe.sub.3]([[mu].sub.3]-O) motif are compared. The overall antiferromagnetic exchange has increased in magnitude in the case of the pyrazolate complex when compared to its analogous carboxylates.

The effects of changing the metal, the pyrazole substitution with most anions, and the number of pyrazole ligands on new pyrazole compounds are examined. The stability of the receptors, the strength of anion binding and the difference in binding strength are used to show that the rhenium receptors with 3,5-dimethylpyrazole or tert-butylpyrazole perform better than complexes of Mo or Mn and than Re complexes with nonsubstituted pyrazole, 3(5)-phenylpyrazole or indazole.

The N,N',O-hetreoscorpionate ligand 1-(4-methoxy-3,5-dimethyl-pyridin-2-yl)-2-methyl-1-pyrazol-1-yl-propan-2-ol (LOH) is synthesized in two high-yield steps. The analysis has disclosed the occurrence of equilibria between different [[Zn[(LOH).sub.2]].sup.2} octahedral isomers and the [[Zn(LOH)Cl].sup.} tetrahedral species.

X-ray crystallography is used to study the synthesis, structure and the properties of manganese(III)-poly(pyrazolyl)borate complexes, which are low-spin in solution and the solid state. The structural changes due to the presence of 3-methyl substituents are equal or more important than the simple metal-ligand bond lengthening in accommodating the steric demands of the 3-methyl groups in bis(Tp*) complexes.

The first examples of trispyrazolylmethane complexes of rare earths are reported. It is indicated that the trispyrazolylmethane ligand is less strongly bound than its anionic trispyrazolyiborate analogues.

The molecular and supramolecular features of three triangular copper(II) propionate secondary building units (SBUs) which form different, self-assembled, 3D metal-organic frameworks (MOFs) are reported. The compounds are remarkably active and selective catalysts or catalyst precursors for the mild peroxidative oxidation of cycloalkanes under mild conditions, into the corresponding alcohols and ketones.

The syntheses of mixed-ligand tetranuclear gold(I) complexes, which result from the reaction of less bulky amidinates and pyrazolates with the bulky ligand dinuclear [[Au.sub.2](2,6-[Me.sub.2]Ph-form).sub.2] is described. It is found that the steric effect of the bulky ligands can block the formation of the tetranuclear species allowing for isolation of the dinuclear and trinuclear complexes.

Different polycatenar pyrazole ligands (Ln) was used to prepare several new cis-[RhCl[(CO).sub.2](Ln)] complexes and obtain columnar liquid crystalline arrangements. The topology of the ligand plays an essential role to induce mesophase at room temperature from a nonmesogenic pyrazole only when it is symmetrically substituted with six decyloxy chains.

The preparation and structural characterization of silver(I) complexes of the arene-linked bis(pyrazolyl)methane ligands m-[[CH[(pz).sub.2]].sub.2][C.sub.6.][H.sub.4], ( and p-[[CH[(pz).sub.2]].sub.2][C.sub.6.][H.sub.4] and 1,3,5-[[CH[(pz).sub.2]].sub.3]C.sub.6.][H.sub.3] is described. The findings reveal that use of the tritopic ligand affords stoichiometry-dependent complexes containing either discrete dimeric metallacycles with equimolar amounts of silver salts and ligand or a polymer of metallacycles in the presence of an excess of silver salt.

The preparation, characterization, and structural models of a number of cadmium- and mercury-containing acetate/pyrazolate species, including a rare example of a polymer built by C-mercuriated pyrazoles is presented. The power diffraction methods using conventional X-ray laboratory equipment, supported by [super 13]C CPMAS NMR measurements helped in assigning a C-metalated nature to an amorphous material of [Hg(ac)-(pz)] formula, obtained by employing EtOH as a solvent.

The representative of P,P,P-trichloroylides-5-methyl-2-phenyl-4-(trichlorophosphoranylidene)2,4-dihydro-3H-pyrazol-3-one was synthesized and characterized. Some chemical properties were studied and compared with one of P,P,P-trichloroylides-5-methyl-2-phenyl-4-(trichlorophosphoranylidene)2,4-dihydro-3H-pyrazol-3-one.

The synthesis of mixed-metal trinuclear gold-silver complexes by the direct reaction of gold(I) carbeniate and gold(I) benzylimidazolate with silver(I) pyrazolate complex is described. This presents a new approach to cluster mixed-metal synthesis with potential use in mixed-metal catalysis.

Azide-bound, two M(II) [M=Mn (1), Ni(2)] monomers capped by 5-methylpyrazole, resulting in 2D supramolecular assemblies formed by hydrogen bonds and [pi]-[pi] contacts and a terephthalate (tp)-bridged Co(II) compound (3) with a 2D sheet structure built by covalent and noncovalent bonds was prepared. Intra- and interchain hydrogen bonds are responsible for the presence of two types of capping ligands in the same coordination sphere and for 3 weak antiferromagnetic interactions through tp are present.

The synthesis and characterization of carbonyloxo- and carbonylsulfidotungsten(IV) complexes containing hydrotris(3,5-dimethylpyrazol-1-yl)-borate is reported. The complex exhibits a symmetrical, binuclear structure with a linear W-O-W unit.

The synthesis and characterization of several 3,5-dimethylpyrazolate (Me(sub 2)pz(super -)) and 3,5-di-tert-butyl-pyrazolate ('Bu(sub 2)pz(super -) complexes of Li(super +), Na(super +), and K(super +) are presented. In these complexes with a dominant ionic bonding, a tendency to form structures which allow the maximization of the interaction between the R(sub 2)pz(super -) ligands and the alkali cations forming a cluster or chain structures is observed.

A series of nanosized cavity-containing bipyrazolate-bridge metallomacrocycles with dimetal centers are synthesized through a directed self-assembly approach involving spontaneous deprotonation of the 1H-bipyrazolyl ligands in aqueous solution. The complexes have weak Pd(II)...Pd(II) or Pt(II)...Pt(II) interactions are characterized by elemental analysis (super 1)H and (super 13)C, NMR, cold-spray ionization or electrospray ionization mass spectrometry, UV-visible spectroscopy and luminesescence spectroscopy.

The synthesis and crystal structure analysis of the ditopic p-phenylene-bridge bis(pyrazol-1-yl)borate ligand [[p-C(sub 6)H(sub 4)-(Bpz(sub 2)tBu)(sub 2)]Li(sub 2)] is described. Reaction of LLi(sub 2) with [Ti(NMe(sub 2))(sub 2)Cl(sub 2)]and water the mu-oxo-bridged dititanium species [L[Ti(NMe(sub 2))Cl](sub 2)(mu-O)] is obtained in excellent yield.

Several elegant methods for the regioselective synthesis of unsymmetrically substituted 1-arylpyrazoles that are reported in the literature are discussed. The 1-phenylpyrazole motif is present in several drug candidates for treatment of various diseases like cyclooxygenase-2 inhibitors, II-1 synthesis inhibitors and protein kinase inhibitors.

Rh(III) diketonate complexes of formula [Cp*M(Q)Cl] (M=Rh or Ir, Cp*=pentamethylcyclopentadienyl, HQ=1-phenyl-3-mthyl-4R(C=O)-pyrazol-5-one) is easily synthesized by reaction of [Cp*MCl2]2 with the adequate sodium salt NaQ. [Cp*M(Q)Cl] complexes exist as enantiomers, both in the solid state and in solution, the mental being a center of chirality. The [Cp*M(Q)Cl] complexes are stable in solid state and in the atmosphere for a long time, and they are also stable in weak polar solvents and up to 55 degree Celsius.

The approaches are reported to achieve efficient blue to near-UV emission from triscyclometalated iridium(III) materials. The approach to tuning the photophysical properties of cyclometalated Ir complexes investigated in the study involved the control of the relative energies of emissive and non-emissive excited states.

The crystal structure of [Cu(Npy2pz)]2(ClO4)2.2CH3CN is determined by x-ray crystallography and it is found to consist of two nearly identical discrete dinucler molecules with bis(pyrazolato) bridges. Variable temperature-dependent magnetic data shows that antiferromagnetic interactions operate in [Cu(Npy2pz)]2(ClO4)2.2CH3CN as a result of the binding angle of the pyrazolato bridge.

A series of heteroleptic Ir(III) metal complexes bearing two N-phenyl-substituted pyrazoles and one 2-pyridyl pyrazole ligands are synthesized and characterized to attain highly efficient, room temperature blue phosphorescence. The results on the basis of steady-state, relaxation dynamics, and theoretical approaches, lead to a conclusion that the weakening of iridium metal-ligand bonding strength in the T1 state plays a crucial role for the fast radiationless deactivation.

A novel one-step synthesis route to fully substituted pyrazol-4-ols is reported. This simple yet nonobvious method for the construction of pyrazol-4-ols by the condensation-fragmentation-cyclization-extrusion reactions of thietanones with 1,2,4,5-tetrazines is reported.

An unusual reaction process that produced unexpected heterocyclic systems by a fragmentation-recombination mechanism is described. Evidence for the mechanism of the formation of the dihydropyrazoles is presented for supporting the novel fragmentation-cycloaddition process.

The ligand substitution behavior of trans- [co (Hdmg)(sub 2)(R) S] is studied for imidazole, pyrazole, 1,2,4-triazole, N- acetylimidazole, 5-chloro-1-methylimidazole, NO (sub 2)-, Ph (sub 3) As, and Ph (sub 3) Sb as entering ligands. In all cases except for Ph (sub 3) As and Ph (sub 3) Sb, the observed kinetics shows a linear dependence on the entering nucleophile concentration with no evidence for a back reaction.

A theoretical study of the TpIrH (sub 4) system is discussed. A comparison of the experimental infrared spectrum of TpIrH4 and harmonic frequency calculations support the assignment of C (sub s) and C (sub i) structures.

Two 3D polyknotted topological isomers that were obtained from the reactions of CuSCN (copper thiocyanate) and (Hbppz) 3,5-bis(4-pyridyl)-1H-pyrazole under different conditions is reported. Both complexes are polyknotted topological isomers introduced by different linkage modes of the SC[N.sup-] anion between two interpenetrating [10.sup.3] networks.

The successful design and synthesis of the new bis(pyrazolyl)-ethanamine ligand and its copper(I) triphenylphosphine complex is reported. The ligand coordinates to the copper(I) center in a fac tridentate fashion, through both the pyrazolyl rings and the nitrogen atom from the N[H.sub.2] group.

A practical and scalable pathway to selective CC[K.sub.1] receptor antagonist is described. The key features in the concise route include a regioselective construction of the pyrazole core through the reaction of an aryl hydrazine and an elaborated acetylenic ketone, a [Tf.sub.2]O/pyridine mediated Z-selective dehydration of an [alpha]-hydroxyester and a stereoselective hydrolysis.

The enantioselective catalysis of 1,3-dipolar cycloaddition reaction of nitrones with propioloylpyrazole and acryloylpyrazole derivatives in presence of a chiral copper(II) complex of 3-(2-naphthyl)-L-alanine amide is described. The reaction is the first successful method for the catalytic enantioselective 1,3-dipolar cycloaddition of nitrones with acetylene derivatives.

Two highly porous coordination polymers, containing rare octanuclear hydroxo-nickel clusters and long bis-pyrazolyl spacers are reported. The polymers are found to possess lattice cavities up to 72% of the total crystal volume after mild thermal treatment.

A novel iridium(III) complex is described, where the complex has shown as intramolecular face-to-face [pi]-stacking between the phenyl ring of the dmppz ligand and the pendant phenyl of the pbpy ligand. The high stability is favored by the presence of pendant methyl groups on the dmppz ligands that has hindered the entrance of water molecules rendering the degradation of the complex more difficult.

1,3-Dipolar cycloaddition reactions of VDCP-diesters with aromatic diazomethanes generated in situ from the aromatic aldehydes and tosylhydrazine mediated by base produce pyrazole derivatives under mild conditions. A plausible reaction mechanism is proposed based on the control experiments along with the discussion on the regioselectivity.

Several studies are conducted to explain the synthesis, characterization, as well as the properties of the various dinuclear Pt(II) 6-(5-t rifluoromethyl-p yrazol-3-yl)-2,2?-bipyridine complexes. The dual phosphorescence exhibited by these dinuclear complexes is also examined.

Catalytic CuI and sparteine have annulated 2-formylpyrroles with o-aminoiodoarenes to produce substituted pyrrolo[1,2-a]quinoxalines and related heterocycles. The reaction has worked for annulation of 2-formylindoles, 2-formylimidazole, 2-formylbenzimidazole and a 3-formylpyrazole.

The cycloaddition of 4-iodosydnones with terminal alkynes has proceeded with good regiocontrol in order to produce 5-iodo pyrazoles. These products have participated in subsequently C-C and C-heteroatom bond forming processes.