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The reaction of select copper(II) monocarboxylates Cu(RCOO)2(H2O)x (R = C4H3O, C6H5, H; x = 2, 4) with pyrazole (Hpz), carried out in protic solvents, yields mono- or dinuclear species [Cu(RCOO)2(Hpz)n]m (n = 2, 4; m = 1, 2), always accompanied by tri- or hexanuclear derivatives based on the triangular [Cu3(μ3-OH)(μ-pz)3]2+ fragment. The molecular structures of all isolated compounds have been established through XRD determinations. In some cases, the mono-, or dinuclear species act as secondary building units, self-assembling into 1D or 3D coordination polymers. The hexanuclear benzoate cluster contains coordinated and crystallization MeOH molecules, whose removal generates a crystalline 1D coordination polymer that can be reconverted into the hexanuclear cluster by soaking in MeOH. The relatively high pKb values of carboxylate anions employed in the syntheses are responsible for the preferential formation of mono- or dinuclear species rather than tri- or hexanuclear ones.

A plausible path for the Cu-3(mu(3)-OH)(mu-Pz)(3) core formation is herein proposed by theoretically modelling the reaction in water between [Cu-2(RCOO)(4)](n), (R = CH3(CH2)(2)) and HPz, which yields the hexanuclear species [{Cu-3(mu(3)-OH)(mu-Pz)(3)(RCOO)(2)(CH3OH)(H2O)}(2)]. We focused on the A -> B reaction (A = [Cu-2(RCOO)(4)(H2O)(2)]; B = [Cu-3(mu(3)-OH)(mu-Pz)(3)(RCOO)(2)(CH3OH)(H2O)]) with the final goal of pinpointing stable intermediates, tightened by experimental conditions, by exploiting the outcomes of numerical experiments carried out in the habit of the density functional theory. (C) 2017 Elsevier B.V. All rights reserved.

A series of copper(II) pyrazolates were synthesized employing different synthetic approaches. By refluxing either [Cu3(μ3-OH)(μ-pz)3(CH3COO)2(pzH)] (pzH = pyrazole) or [Cu(μ-pz)2·H2O]n in water, [Cu(μ-pz)(μ-OH)]n (1) was unexpectedly obtained, whereas the reactions of copper(II) acetate hydrate with pzH or 4-XpzH (4-XpzH = 4-Xpyrazole, X = Cl, Br, I) in dimethylformamide (DMF) by microwave-assisted solvothermal syntheses yielded the compounds [Cu(μ-pz)2(μ-DMF)]n (2DMF) or [Cu(μ-4-Xpz)2(μ-DMF)]n (3DMF–5DMF). As unveiled by powder X-ray diffraction, all these compounds are 1-D coordination polymers showing square planar trans-CuN2O2 (1) or octahedral trans-CuN4O2 (2DMF–5DMF) metal centers, reasonably involved in through-bond antiferromagnetic interactions (magnetic susceptibility in the range 0.91–1.56 B.M.). Theoretical calculations carried out on these compounds at the B3LYP-D* level confirmed the structural aspects and IR spectroscopy features unveiled experimentally. Upon heating, 2DMF–5DMF reversibly lose DMF to give the corresponding low-crystallinity coordination polymers [Cu(μ-pz)2]n (2) and [Cu(μ-4-Xpz)2]n (3–5), of which only 3 was characterized in the past. In order to shed light on the local-level structural features of 2, 4 and 5, UV-Vis-NIR absorption and fluorescence emission spectroscopy measurements were performed, the results suggesting a tetrahedral stereochemistry for the metal centres.

The reaction of copper(II) chloroacetate (1d) with pyrazole (Hpz) mainly yielded the mononuclear compound [Cu(μ-ClCH2COO)2(Hpz)2] (2m), which self-assembled generating a one-dimensional coordination polymer. Moreover, the concomitant isolation of the tetranuclear [{Cu2(μ-pz)(μ-OCH2COO)(Hpz)(MeOH)}2(μ-ClCH2COO)2] (3t) and hexanuclear [{Cu3(μ3-OH)(μ-pz)3(Hpz)2}2(μ-ClCH2COO)2](Cl)2 (4h) species evidenced the occurrence of a peculiar, previously unreported, dehydrochlorination reaction and the formation of the trinuclear triangular moiety [Cu3(μ3-OH)(μ-pz)3]. Theoretical calculations based on density functional theory including solvation effects indicate a possible pathway for the formation of 3t. Interestingly, besides the energy minimum corresponding to 3t, a further relative energy minimum is found for a species which can be considered a possible reaction intermediate.

The reactions of 4,4'-bipyridine with selected trinuclear triangular copper(II) complexes, [Cu-3(mu(3)-OH)(mu-pz)(3)(RCOO)(2)L-x], [pz = pyrazolate anion, R = CH3(CH2)(n) (2

[object Object]Different synthetic procedures lead to different coordination polymers (CPs) based either on the trinuclear triangular [Cu3(? 3-OH)(?-pz)3]2+ or on the mononuclear [Cu(Hpz)3]2+ (Hpz=pyrazole) secondary building units (SBUs), bridged by the flexible glutarate (Glu) dianion. The mononuclear complex [Cu(HGlu)2(Hpz)4] was also obtained as byproduct. One of the CPs based on the trinuclear SBU displays a relevant porosity due to three intersecting channels, accounting for about 40% of the solvent accessible void space.

By reacting 4,4′-bipyridine (bpy) with selected trinuclear triangular CuII complexes, [Cu3(μ3-OH)(μ-pz)3(RCOO)2(LL′)] [pz = pyrazolate anion; R = CH3, CH3CH2, CH2═CH, CH2═C(CH3); L, L′ = Hpz, H2O, MeOH] in MeOH, the substitution of monotopic ligands by ditopic bpy was observed. Depending on the stoichiometric reaction ratios, different compounds were isolated and structurally characterized. One- and two-dimensional coordination polymers (CPs), as well as two hexanuclear CuII clusters were identified. One of the hexanuclear clusters self-assembles into a supramolecular three-dimensional structure, and its crystal packing shows the presence of two intersecting channels, one of which is almost completely occupied by guest bpy, while in the second one guest water molecules are present. This compound also shows a reversible, thermally induced, single-crystal-to-single-crystal transition.

Nanostructured (d similar to 20-35 nm) and highly luminescent Ca(OH)(2):Ln and Mg(OH) 2: Ln (Ln Eu-III, Sm-III, Tb-III, Mg(Ca)/Ln = 20 : 1 atomic) nanostructures were obtained in inverse (water in oil - w/o) miniemulsion (ME), by exploiting the nanosized compartments of the droplets to spatially confine the hydroxide precipitation in basic environment (NaOH). The functional nanostructures were prepared using different surfactants (Span80 (span) and a mixture of Igepal co-630 and Brij 52 (mix)) to optimise ME stability and hydroxide biocompatibility as well as tune the droplet sizes. X-Ray diffraction (XRD) analyses testify the achievement of a pure brucite-Mg(OH)(2)-phase and pure portlandite-Ca(OH)(2)-phase with a high degree of crystallinity. Besides structural characterisations, the products were thoroughly characterised by means of several and complementary techniques (dynamic light scattering (DLS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), micro-Raman spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS) and Fourier transform infrared spectroscopy (FT-IR)) to assess their chemicophysical properties as well as their morphological and microstructural features. The stoichiometry of the doped systems was confirmed using ICP-MS measurements. Finally, the cytotoxicity of the nanoparticles was assessed by in vitro tests using ES2 cells in order to provide preliminary data on the biocompatibility of this kind of nanoparticles. The luminescence of the Eu-doped and Tb-doped materials is clearly visible to the naked eye in the red and green regions, respectively, corroborating their employment as materials for imaging in the optical window of interest.

By reacting 4,4'-bipyridine (bpy) with selected trinuclear triangular Cu-II complexes, [Cu-3(mu(3)-OH)(mu-pz)(3)(RCOO)(2)(LL')] [pz = pyrazolate anion; R = CH3, CH3CH2, CH2=CH, CH2=C(CH3); L, L' = Hpz, H2O, MeOH] in MeOH, the substitution of monotopic ligands by ditopic bpy was observed. Depending on the stoichiometric reaction ratios, different compounds were isolated and structurally characterized. One- and two-dimensional coordination polymers (CPs), as well as two hexanuclear Cu-II clusters were identified. One of the hexanuclear clusters self-assembles into a supramolecular three-dimensional structure, and its crystal packing shows the presence of two intersecting channels, one of which is almost completely occupied by guest bpy, while in the second one guest water molecules are present. This compound also shows a reversible, thermally induced, single-crystal-to-single-crystal transition.

A quick, easy and green water-based synthesis protocol involving coprecipitation of oxalates combined with hydrothermal treatment resulted in the crystallisation of nanostructured manganites at a relatively low temperature (180 °C). The subcritical hydrothermal approach was shown to play a key role in stabilising phases which are generally achieved at much higher temperatures and under harsher conditions, thus disclosing an exciting alternative for their synthesis. Through this mild wet chemistry approach, the compounds CuMnO2, ZnMn2O4 and ZnMnO3 were synthesised as nanocrystalline powders. Noticeably, the optimised route proved to be effective in stabilising the exotic polymorph cubic spinel ZnMnO3 in pure form. This is particularly notable, as very few records concerning this compound are available in the literature. The compounds were fully characterised from compositional, structural, morphological and magnetic points of view.

none 9 The reaction of some saturated and unsaturated aliphatic copper(II) monocarboxylates, Cu(RCOO)2 [R = C6H5CH2 (phenylacetate, Phac), CH2[dbnd]CHCH2 (vinylacetate, Vnac), C6H5CH[dbnd]CH (3-trans-phenylacrylate, Phacr), C6H5(CH2)2 (3-phenylpropionate, Phpr), c-C6H11 (ciclo–hexylcarboxylate, c-Hexc), CH3(CH2)10 (laurate, Lau), CH3(CH2)12 (myristate, Myr), (CH3)3C (pivalate, Piv)] with pyrazole (Hpz) and water in protic solvents, yielded trinuclear triangular derivatives based on the [Cu3(μ3-OH)(μ-pz)3] fragment whose double positive charge is balanced by two coordinated carboxylate ions, actually [Cu3(μ3-OH)(μ-pz)3(Phac)2], 1, [Cu3(μ3-OH)(μ-pz)3(Vnac)2(Hpz)], 2, [Cu3(μ3-OH)(μ-pz)3(Phacr)2], 3, [Cu3(μ3-OH)(μ-pz)3(Phpr)2(Hpz)Cu3(μ3-OH)(μ-pz)3(Phpr)2(Hpz)(H2O)]·xH2O·yMeOH, 4, [Cu3(μ3-OH)(μ-pz)3(c-Hexc)2], 5, [Cu3(μ3-OH)(μ-pz)3(Lau)2], 6, [Cu3(μ3-OH)(μ-pz)3(Myr)2], 7, [Cu3(μ3-OH)(μ-pz)3(Piv)2(HPz)(HPiv)2], 8. This behavior is consistent with some previously observed features and evidences that the basicity of carboxylate ions is the key for the deprotonation of Hpz and water, leading to the formation of pz− and OH− ions, which are determinant for the self-assembly of the trinuclear triangular species. Single crystal XRD determinations evidenced that in compounds 1, 2 and 5 the trinuclear moieties further self-assemble generating monodimensional coordination polymers or, in one case (compound 4), a dodecanuclear discrete assembly. Massignani, Sara; Scatena, Rebecca; Lanza, Arianna; Monari, Magda; Condello, Francesca; Nestola, Fabrizio; Pettinari, Claudio; Zorzi, Federico; Pandolfo, Luciano Massignani, Sara; Scatena, Rebecca; Lanza, Arianna; Monari, Magda; Condello, Francesca; Nestola, Fabrizio; Pettinari, Claudio; Zorzi, Federico; Pandolfo, Luciano

In the past decade great effort has been put into the development of synthetic strategies to produce trinuclear triangular CuII (TTC) arrays, which may be synthetic analogues of the trinuclear site in ascorbate oxidase and blue oxidase. A large number of scientific contributions have been dedicated to the synthesis and spectroscopic characterization of TTC arrays. In contrast, only a small number of studies deal with their possible applications. As a consequence, systematic studies describing their reactivity are very rare and the few existing models can only partially explain how structural and molecular parameters influence their reactivity and their possible uses and applications. This contribution reports a summary of all experimental results related to the Cu3(μ3-OH)(μ-pz)3 core (pz = unsubstituted pyrazolate). We describe here all species, distinguishing them according to whether they are neutral, cationic or anionic, as well as their main structural features, the synthetic procedures employed for their production, their reactivity toward nucleophiles and strong acids and, finally, their possible and perspective applications.

The trinuclear triangular CuII complex [Cu3(μ3-OH)(μ-pz)3(HCOO)2(Hpz)2] (Hpz = pyrazole) reacts with 4,4′-bipyridine (bpy) yielding a two-dimensional (2D) waved sheets, two three-dimensional (3D) c...

A series of mono-, tri-, hexanuclear compounds, and coordination polymers were obtained from the reaction of [Cu3(μ3-OH)(μ-pz)3(MeCOO)2(Hpz)], 1, (Hpz = pyrazole) with H2SO4, H3PO4, HClO4, HNO3, CF...

Density functional theory has been used to study the electronic structure of [M(tp)] and [M(tpm)](+) conformers (M = Cu, Ag; tp = tris(pyrazol-1-yl)borate anion, tpm = tris(pyrazol-1-yl) methane) and the energetics of their interconversions. Results for the free tp ligand are similar to those of tpm [M. Casarin, D. Forrer, F. Garau, L. Pandolfo, C. Pettinari, A. Vittadini, J. Phys. Chem. A 112 (2008) 6723], indicating an intrinsic instability of the tripodal conformation (kappa(3)-like). This points out that, though frequently observed, the kappa(3)-coordinative mode is unlikely to be directly achieved through the interaction of M(I) with the kappa(3)-like tp/tpm conformer. Analogously to the [M(tpm)](+) molecular ions, the energy barrier for the kappa(2)-[M(tp)] -> kappa(3)-[M(tp)] conversion is computed to be negligible. Though kappa(n)-[M(tp)] and kappa(n)-[M(tpm)](+) (n = 1, 2, 3) have similar metal-ligand covalent interactions, the negative charge associated to the tp ligand makes the M-tp bonding stronger.

From the reaction of Cu(Pht)(H2O) (Pht = o-benzene dicarboxylate) with pyrazole (Hpz), four different 1D or 2D Coordination Polymers (CPs), [Cu(Pht)(Hpz)(2)]center dot CH2Cl2, 1, [{Cu(Pht)(Hpz)(4)}(3)]center dot 3.5Hpz center dot H2O, 2, [{Cu(Pht)(Hpz)(2)}(2)center dot 0.5H(2)O], 3, and [Cu(Pht)(Hpz)(2)], 4, where Pht dianions bridge two or three mononuclear Cu(Hpz)(x) moieties (x = 2, 4), as well as the compound [Cu(Pht)(Hpz)(4)]center dot MeOH, 5, have been obtained, depending on the solvent employed. All compounds are air stable and have been characterized through elemental analyses and spectral determinations (IR, ESI-MS, magnetic susceptibility) and 1-4 also by single crystal X-ray diffraction studies. The self-assemblies of compounds 1-4 in different solvents generate different 1D and 2D CPs as a consequence of the presence of different crystallization solvent molecules in the supramolecular cavities.

Hydrated zinc(II) formate reacts with 2,2′-bipyridine (2,2′-bpy) to form a novel zig-zag mono-dimensional coordination polymer (1D CP) [{Zn(μ-OCHO)(OCHO)(2,2′-bpy)(HO)}·HO], 1, which was structurally characterized by a single-crystal X-ray diffraction study. Title compound crystallizes in the orthorhombic system, Pbca space group, [a = 6.7651(8), b = 17.4876(19), c = 23.180(3)]. Each zinc ion displays a distorted octahedral geometry due to the coordination of a monotopic formate, one molecule of water and the two nitrogen atoms of 2,2′-bpy, while the octahedral scheme is completed by the coordination of a ditopic formate connecting two zinc ions according to a syn-anti configuration, thus generating the polymeric structure. Moreover, a crystallization water molecule acts as a supramolecular bridge connecting formate ions belonging to neighboring, symmetry equivalent, 1D CPs through quite strong H-bonds, thus leading to an overall waved 2D open framework. Thermal analyses show significant weight losses corresponding to the elimination of water molecules followed by the decomposition of both formate groups and 2,2′-bipyridine., Financial support from the University of Camerino, the Junta de Andalucía (Grant 2009/FQM-4826) and CSIC (Grant PIF/2008-017-1) is gratefully acknowledged.

The almost quantitative formation of the triangular trinuclear copper derivative [Cu3(μ3-OH)(μ-pz)3(MeCOO)2(Hpz)] (1) (Hpz = pyrazole), has been simply achieved by adding Hpz to an ethanol solution of Cu(MeCOO)2·H2O. An X-ray molecular structure determination shows that 1 is completely unsymmetric and that trinuclear units result assembled in an extended bidimensional network formed through acetate bridges and hydrogen bonds. EPR and magnetic measurements are consistent with the presence of a single unpaired electron. Theoretical density functional calculations carried out for S = 1/2 provide a thorough description of the electronic structure of 1, allowing a detailed assignment of its UV−vis absorption spectrum. Compound 1 reacts with MeONa, yielding [Cu3(μ3-OH)(μ-pz)3(MeCOO)(MeO)(Hpz)] (2) and [Cu3(μ3-OH)(μ-pz)3(MeO)2(Hpz)] (3) through the substitution of one and two acetate ions, respectively, with MeO- ion(s). The spontaneous self-assembly of the triangular trinuclear Cu3 moiety seems to occur only wi...

Quasi-relativistic density functional calculations have been used to look into the molecular and electronic properties of cis-[Pt(η3-C3H5){η1-C(PPh3)(CO)}2]BF4. Numerical experiments have been run for both isomers compatible with IR and NMR outcomes. Binding energies and computed CCO stretching frequencies are very similar for both species, thus indicating their possible coexistence in solution. The comparison with homogeneous theoretical data pertaining to cis/trans-[Pt(η3-C3H5)2] and trans-[PtCl2{η1-C(PPh3)(CO)}2] provides a rationale of the [Pt(η3-C3H5){η1-C(PPh3)(CO)}2]BF4 low stability.

Ketenylidenetriphenylphosphorane, Ph 3 PCCO ( 1 ), presents, at a first glance, the characteristics of both ylides and ketenes, but its behavior is that typical of ylides, undergoing electrophilic attacks on the ylidic carbon that transform 1 into a ‘true’ ketene having PPh 3 as one substituent. Here we review the synthesis, the chemical–physical properties as well as the reactivity of these compounds, with a particular emphasis on the interaction with transition metal complexes. With this compound it has always been observed that the ylidic carbon of 1 binds to coordinatively unsaturated metals, which act as electrophiles, forming η 1 -ketenyl derivatives that can also be viewed as stabilized metal-substituted ketenes. Perspectives for the synthesis of other metal-substituted ketenes and developments on their study are also presented.

The controlled, room-temperature synthesis of M-doped (M = CuII, MnII, SmIII, GdIII, or TbII) ZnS nanostructures (with an average crystallite size of 5-10 nm) in the confined space of miniemulsion droplets is reported herein and discussed. The adopted synthetic route is a colloidal method, ideally suited to easily achieve small particle size and narrow size distribution. The synthesized functional nanostructures crystallize in the sphalerite lattice, as determined by powder X-ray diffraction. In addition to structural characterization, several complementary techniques, such as X-ray photoelectron spectroscopy, thermogravimetric analysis, differential scanning calorimetry, micro-Raman spectroscopy, inductively coupled plasma mass spectrometry, and Fourier transform infrared spectroscopy were used to determine chemical and physical properties as well as the microstructural features of our products. As far as the morphological aspects of the obtained samples are concerned, they were studied by means of scanning and transmission electron microscopies. Finally, the local structure around dopant ions was unravelled by means of X-ray absorption spectroscopy, in particular through extended X-ray absorption fine structure measurements carried out at the Zn, S, and dopant K or L3 edges. This information has been complemented with the investigation of the photoluminescence properties.

The low-lying empty orbitals of bis(acetylacetonato)copper have been probed by near-edge X-ray absorption fine structure (NEXAFS) spectroscopy at the Cu L2,3 edges and time-dependent density functional theory (TDDFT) calculations within the Tamm-Dancoff approximation (TDA) coupled to the relativistic zeroth-order regular approximation including spin-orbit effects (SO-ZORA TDDFT-TDA). Both the relative positions of NEXAFS features and their linear dichroism are satisfactorily reproduced. Moreover, a comparison with literature data pertaining to two other square-planar CuII complexes ([CuCl4]2- and copper phthalocyanine) provided information about how metal-to-ligand charge-transfer transitions associated with excitations from CuII 2p orbitals to low-lying, ligand-based ?* molecular orbitals in a simplified one-electron picture may contribute to the CuII L2,3 edge intensity and, thus, weaken its believed relationship with the CuII-ligand symmetry-restricted covalency.

Cross-polarization, combined with magic-angle spinning, has been employed to obtain high-resolution solid-state 13C and 31P NMR spectra of a series of solid, peculiar ketenes, also known as η1-ketenyl derivatives, bearing as substituents a PPh3 moiety and a coordinatively unsaturated Pt(II) fragment. Solid-state NMR data found for trans-[PtCl2(η2-C2H4){η1-C(PPh3)CO}], trans-[PtCl2{η1-C(PPh3)CO}2], Ph3PCCO, trans-[PtCl2(η2-C2H4){η1-CH(PPh3)COMe}], trans-[PtCl2{η1-CH(PPh3)COMe}2] and Ph3PCHCOMe, are compared with NMR values obtained in solution. The general utility of the CP/MAS NMR technique in the study of unstable or insoluble complexes is discussed.

Mono- and bis-η1-ketenyl Pt(II) complexes have been synthesized by reacting Zeise's salt or the related dimeric compound, [{PtCl2(C2H4)}2], with the oxocumulenic ylide ketenylidenetriphenylphosphorane, Ph3PCCO, 1, in suitable ratios. In particular, the η1-ketenyl derivative, trans-[PtCl2(C2H4){η1-C(PPh3)CO}], 2, has been isolated and characterized. The reaction of 2 with one more equivalent of 1 displaces the coordinated ethylene giving the first stable bis-η1-ketenyl derivative, trans-[PtCl2{η1-C(PPh3)CO}2], 6. The X-ray crystal structure of 6 shows a trans centrosymmetric geometry around Pt, with the PCCO moiety and the metal lying in a plane that forms an angle of ∼65° with the Pt(II) coordination plane. Density functional calculations indicate that steric effects play a leading role in determining such an arrangement. Data on the reactivity of 2 and 6 are also reported.

Ketenylidenetriphenylphosphorane, Ph 3 PCCO, 1 , has been used to synthesize some Pt(II) η 1 -ketenyl derivatives, through reactions with dimeric and tetrameric chlorine-bridged compounds. Particularly it has been possible to isolate and characterize [Pt(η 3 -C 3 H 5 )Cl{η 1 -C(PPh 3 )CO}], 2 , and [PtCl 2 {η 1 -C(PPh 3 )CO}(PPh 3 )], 3 . Moreover, the reaction of 2 with a further equivalent of 1 , in the presence of AgBF 4 , lead to the formation of [Pt(η 3 -C 3 H 5 ){η 1 -C(PPh 3 )CO} 2 ], 4 , the first bis-η 1 -ketenyl derivative. Compound 4 is stable in solution only at low temperatures and its formation has been inferred unequivocally by IR, 1 H and 31 P-NMR measurements carried out at −50°C.

In this study are reported the syntheses of three bis(diarylhydrazonecarbonyl)methylene derivatives [{ArPhCNNHC(O)}2CH2] [Ar = 2C5H4N (5), C6H5 (6), and 2-C4H3S (7)], obtained by condensation of corresponding hydrazones with carbon suboxide, C3O2. The solid-state self-assembly of these carbonyl derivatives, giving rise to polymeric and dimeric networks, is described. In the formation of these structural features, in addition to N—H· · ·OC intermolecular hydrogen bonds, stabilizing intramolecular NH· · · π (systems) and intermolecular CO· · ·π (systems) interactions also seem to play an important role. Solution 1H-nmr data of compounds 5–7 indicate that the polymeric and dimeric structures are not maintained in solution and show the occurrence of keto-enolic equilibria. © 1999 John Wiley & Sons, Inc. Biopoly 49: 541–549, 1999

The molecular and electronic structure of hexakis[m-(dimethylarsinodithioate-S:S')]-m(4)-thioxotetrazinc has been investigated by combining X-ray diffraction measurements, electrospray mass spectrometry (ESI), UV absorption spectroscopy, and density functional calculations. The polynuclear zinc complex consists of discrete "tetrazinc sulfide" moieties held together by van der Waals interactions. The unit cell contains four independent molecules and four solvent molecules. Each independent unit is characterized by a central m(4)-S coordinated to four Zn ions, each of them at the center of an irregular tetrahedron of S atoms. ESI measurements point out that the synthesis of the analogous Cd derivative was successful. Crystal data are as follows: chemical formula, C(12)H(36)As(6)Cl(1.5)S(13)Zn(4); monoclinic space group P2(1)/n (no. 14); a = 30.4228(7) A, b = 18.3720(5) A, c = 32.3758(8) A, beta = 95.857(1) degrees; Z = 16. Theoretical calculations indicate that, despite their structural arrangement, neither the Zn nor the Cd complex can be considered molecular models of the extended ZnS and CdS. Nevertheless, the electronic transitions localized in the Zn(4)(m(4)-S) and Cd(4)(m(4)-S) inner cores of the title compounds have the same nature as those giving rise to the maxima in the excitation spectra of the extended Zn(4)S(BO(2))(6) and Cd(4)S(AlO(2))(6) [Blasse, G.; Dirksen, G. J.; Brenchley, M. E.; Weller, M. T. Chem. Phys. Lett. 1995, 234, 177].

The gas phase ion/molecule reactions of the title ionic species with carbon suboxide have been studied by ion trap mass spectrometry and interpreted as the result of electrophilic addition of these ions on the electron-rich central carbon of C3O2 followed by CO loss. © 1998 John Wiley & Sons, Ltd.

The coordination and organometallic chemistry of P- and As-carbonyl stabilized ylides is reviewed. As a general feature, the coordination chemistry of R3ECHCOR′-type (E=P, As) ligands appears to be dominated by C(ylide) metal coordination, although a few examples of O(ylide)-bound complexes are known. The factors addressing C(ylide)-vs. O(ylide)-coordination in Pt(II) and Pd(II) systems are examined. The Ni(II) complexes containing P,O-chelate ylide ligands are also discussed, with a special emphasis on their catalytic activity. The synthesis and reactivity of phosphonium functionalized isocyanides and their corresponding ylides, which provide a new route to metal coordinated indole systems, are described. Finally, the reactivity of Ph3PCCO towards metal substrates is summarized including the formation of ketenyl complexes.

Crystalline and nanostructured cobalt (CoFe2O4), nickel (NiFe2O4), zinc (ZnFe2O4) and manganese (MnFe2O4) spinel ferrites are synthesized with high yields, crystallinity and purity through an easy, quick, reproducible and low-temperature hydrothermal assisted route starting from an aqueous suspension of coprecipitated metal oxalates. The use of water as a reaction medium is a further advantage of the chosen protocol. Additionally, the zinc spinel is also prepared through an alternative route combining coprecipitation of oxalates from an aqueous solution with thermal decomposition under reflux conditions. The nanocrystalline powders are obtained as a pure crystalline phase already at the extremely low temperature of 75 A degrees C and no further thermal treatment is needed. The structure and microstructure of the prepared materials is investigated by means of X-ray powder diffraction (XRPD), while X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) analyses are used to gain information about the surface and bulk composition of the samples, respectively, confirming the expected stoichiometry. To investigate the effect of the synthesis protocol on the morphology of the obtained ferrites, transmission electron microscopy (TEM) observations are performed on selected samples. The magnetic properties of the cobalt and manganese spinels are also investigated using a superconducting quantum device magnetometer (SQUID) revealing hard and soft ferrimagnetic behavior, respectively.

Three Pt(II) η3-allylic compounds, [Pt(η3-allyl)XP(C6H5)3] (X = Cl, Br, I) have been studied under electrospray ionization (ESI) conditions. Unexpected behaviour, such as the complete lack of either [M]+. or [MH]+ ions, the formation of complexes with the solvent and bis-triphenylphosphino-containing species, was observed. To rationalize such results, a series of parallel measurements on the same compounds have been performed under electron impact, fast-atom bombardment and field ionization conditions. The data so obtained suggest that molecular species are not produced by ESI, probably due to the action of strong electric fields and collisionally induced decompositions occurring in different regions of the instrument. Complexes with the solvent originate through gas-phase ion–molecule reactions, while the bis-triphenylphosphino-containing species are formed by reaction of ions with triphenylphosphine formed by thermal decomposition inside the heated capillary line, just after the electrospray ionization source. © 1997 John Wiley & Sons, Ltd.

The anti-ischaemic effects of amlodipine were compared with those of sustained release nifedipine in 53 patients with exertional angina. After a 1-week drug washout phase, patients were randomised to receive amlodipine (5mg once daily) or sustained release nifedipine (20mg twice daily). After 2 weeks of treatment, initial doses were doubled if there was inadequate control of symptoms in the absence of adverse events.

The reaction of RhCl 3 ·3H 2 O with ( EEE )-1,5,9-cyclododecatriene in alcohols gives a red polymeric solid compound with chlorine bridges, 1 , in which the hydrocarbon moiety has been reported to be bonded to the metal via an η 3 -allylic bond. Re-examination of this reaction has led to the isolation of soluble derivatives obtained by breaking the chlorine bridges with chelating diphosphines and diamines. An X-ray analysis on single crystals of a diphosphino and a diamino derivative, indicates that the cyclo-olefin residue with composition C 12 H 17 has undergone isomerization. The two double bonds not involved in the bonding to the metal are 5,8 rather than 5,9.

By reacting water solutions of pyrazole (Hpz) with copper(II) fumarate or 2-methylfumarate in solvothermal conditions two almost identical trinuclear triangular complexes, [Cu3(μ3-OH)(μ-pz)3{R(COO)2}(Hpz)], [R = CH CH, C(CH3) CH], have been obtained. The two carboxylate groups of both fumarate and 2-methylfumarate show different arrangements, one acting as monotopic ligand while the other one has a ditopic behavior. Thus, in both cases, wavy 2D isomorphous Coordination Polymers (CPs), that further self-assemble through strong H-bonds into two 3D networks, have been obtained. When copper(II) 2-methylfumarate was reacted with pyrazole at r.t. the mononuclear [Cu(Hpz)2(H2O)(2-methylfumarate)·H2O] complex was, in addition, obtained. In this case the bridging dianions produce instead monodimensional CPs that self-assemble into supramolecular tapes mediated by H-bond interactions, involving coordinated and crystallization water molecules. The mononuclear and trinuclear species were preliminary tested as catalysts for the oxidation of styrene by H2O2.

Experimental and theoretical results pertaining to [Zn-10(mu(4)-S)(mu(3)-S)(6)(Py)(9)(SO4)(3)], a possible molecular model of ZnS S-terminated polar surfaces, as well as a potential source of strictly monodispersed ZnS quantum dots, are presented and discussed. The results of density functional theory (DFT) calculations provided a rationale for the peculiar arrangement of [Zn-10(mu(4)-S)(mu(3)-S)(6)(Py)(9)(SO4)(3)] clusters in the solid state, contemporarily indicating the unsuitability of the isolated species to mimic whatever (polar or non-polar) ZnS surface. Despite the fact that such a failure is further confirmed by time-dependent DFT and UV-Vis diffuse reflectance spectroscopy, the combined use of theoretical outcomes, DRIFT measurements, and literature data pertaining to the surface chemical properties of ZnS (Hertl in Langmuir 4:594, 1988) ultimately testifies that [Zn-10(mu(4)-S)(mu(3)-S)(6)(Py)(9)(SO4)(3)] is perfectly suited to model the interaction of pyridine molecules with ZnS surface Lewis acid sites. The herein reported theoretical results are expected to be a useful reference for the interpretation of chemisorption experiments of Py-based Lewis bases on single crystal ZnS surfaces.

The prochiral peroxometallacyclic ketenyl platinum complex [(PPh3)2 PtOOC(O)C CO] (1) reacts with (S)-(−)-α-methylbenzylamine to give the diastereomeric amidic derivatives, 2. One of the two possible diastereomers, 2a, has been obtained pure and the absolute configuration at the carbon atom σ-bonded to the metal is inferred from its CD spectrum. Compound 2a has been used to oxidize the chiral racemic phosphine (RS)-PPhCyPr using a molar ratio, PPhCyPr 2a = 2: 1. The reaction products contains an enantiomeric excess of (S)-(−)-OPPhCyPr whereas unreacted PPhCyPr shows the prevalent (S) configuration, indicating that the reaction occurred with asymmetric induction. These findings are rationalized by a mechanism based on the coordination to the metal of PPhCyPr mainly in the (R) configuration, followed by an intramolecular oxidation by the peroxide moiety.

The gas-phase, ion molecule reaction between C 3 O 2 +. and C 3 O 2 has been studied by both double-focusing and ion trap mass spectrometry, rationalized by the formation of a dimeric, odd electron cation [C 6 C 4 ] +. which decomposes extensively through sequential CO losses giving rise to [C 5 O 3 ] +. and [C 4 O 2 ] +. ions. The thermodynamics of this process have been investigated by means of ab initio calculation performed on the above species using different basis sets (STO-3G, 3-21G and 6-31G*)

The HfIV-oxothiocluster, [Hf4(η2-μ2-SAc)4(η2-μ2-SAc)2(η2-μ2-BuO)4(η2-BuO)2(μ3-O)2], was synthesized by reaction of hafnium butoxide with thioacetic acid. The crystal structure shows the presence of a planar tetranuclear Hf4 core, in which the metal atoms are μ3-O bridged and the thioacetate ligands coordinate the Hf ions both through a bridging and a chelating mode. The structural findings are confirmed by multinuclear NMR spectroscopic data.

The formylketenyl platinum complex, trans-bis(tricyclohexylphosphine)(η1-formylketenyl)(hydride)platinum(II), trans-(PCy3)2(H)Pt[η1-C(CHO)CO] (1), reacts with acids causing the cleavage of the PtC bond and generating the species C3H2O2 which is trapped by an excess of 1. The reaction gives rise to the formation of the addition product trans-(PCy3)2(H)Pt(C6H3O4), where C6H3O4 is an α-pyrone ligand σ-bonded to Pt. The crystal structure of the Pt α-pyrone derivative has been determined. The crystal are monoclinic, space group P21/a, with a = 19.404(9), b = 11.889(6), c = 18.534(9), β = 91.3(1)°, Z = 4. The plane of the α-pyrone ligand is almost orthogonal to the coordination plane of Pt. IR, 1H and 31P NMR and mass spectra also support the structure.

A formyl ketenyl platinum derivative, trans-μ1-(PCy3)2(H)Pt[C(CHO)CO] (where Cy represents a cyclohexyl group), when reacted with HCl, gives a C3H2O2 species among the reaction products. The structure was investigated mass spectrometrically by study of the reactions of metastable ions, and the information gained was combined with data from theoretical calculations to rationalize the structure of the C3H2O2 molecule.

Carbon suboxide, C3, O2, reacts with a great variety of organometallic compounds. With organo-silicon and aluminium compounds it reacts with the C˭O moiety, giving sililation and carboalumination reactions. Insertion reactions of C˭C are performed with compounds having M-H, M-OR, M-NR2, M-PR2 bonds (M ≠ Si, Al), giving mono-metal derivatives (ketenyl) or di-metal derivatives of acil groups (amides, esthers, phospides). The coordination of C˭O or C˭C to transition metal complexes, the formation of allenic compounds and the decarbonylation reactions allow the synthesis of a series of particular metal derivatives (ketenyl, ketenylidene and carbonyl complexes) which, in some cases, present a peculiar reactivity.

The coordination and organometallic chemistry of P- and As-carbonyl stabilized ylides is reviewed. As a general feature, the coordination chemistry of R3ECHCOR′-type (E=P, As) ligands appears to be dominated by C(ylide) metal coordination, although a few examples of O(ylide)-bound complexes are known. The factors addressing C(ylide)-vs. O(ylide)-coordination in Pt(II) and Pd(II) systems are examined. The Ni(II) complexes containing P,O-chelate ylide ligands are also discussed, with a special emphasis on their catalytic activity. The synthesis and reactivity of phosphonium functionalized isocyanides and their corresponding ylides, which provide a new route to metal coordinated indole systems, are described. Finally, the reactivity of Ph3PCCO towards metal substrates is summarized including the formation of ketenyl complexes.

The preparation, characterization, and optimization of the functional properties of mono- and polynuclear coordination complexes containing heteroaromatic nitrogen ligands are discussed here, taking the advantage of numerous studies performed in our laboratories on exploring a variety of different metal ions and polytopic ligands. We highlight how very minor changes in connectivity, composition, and polarity of the molecular entities employed in the self-assembly steps may significantly affect the structural, thermal, sorptive, magnetic, and mesomorphic behavior of the resulting materials. Examples from three different classes are included: 1) pyrazolate-based polynuclear coordination compounds, 2) homoleptic and heteroleptic coordination polymers, and 3) 2,2'-bipyridine metal-based liquid crystals.

The preparation, characterization, and optimization of the functional properties of mono- and polynuclear coordination complexes containing heteroaromatic nitrogen ligands are discussed here, taking the advantage of numerous studies performed in our laboratories on exploring a variety of different metal ions and polytopic ligands. We highlight how very minor changes in connectivity, composition, and polarity of the molecular entities employed in the self-assembly steps may significantly affect the structural, thermal, sorptive, magnetic, and mesomorphic behavior of the resulting materials. Examples from three different classes are included: 1) pyrazolate-based polynuclear coordination compounds, 2) homoleptic and heteroleptic coordination polymers, and 3) 2,2'-bipyridine metal-based liquid crystals.