A phosphine-stabilized silylene rhodium complex.

The first phosphine-stabilized cationic rhodium silylene complex is reported. A dihydrido-silylene-Rh(iii) compound reacts with water and alcohols forming alkoxysilyl-Rh(iii) complexes and hydrogen gas. Moreover, benzophenone reacts with a cationic silylene rhodium complex leading to the reduction of the carbonyl group and the formation of an alkoxysilyl-Rh(iii) compound which has been identified as a likely intermediate in the mechanism for the hydrosilylation of ketones proposed by Hofmann and Gade.

Effect of the change of the ancillary carboxylate bridging ligand on the SMM and luminescence properties of a series of carboxylate-diphenoxido triply bridged dinuclear ZnLn and tetranuclear Zn2Ln2 complexes (Ln = Dy, Er).

Eleven new dinuclear and tetranuclear compounds of general formulae [Zn(µ-L)(µ-X)Ln(NO3)2]·nS, [Zn2Dy2(µ3-L')2(µ-sal)2(NO3)(CH3OH)](NO3)·5CH3OH and [Zn2Er2(µ3-L')2(µ-sal)2(CH3OH)2](NO3)2·4CH3OH (X = benzoate, anthracenate, diclofenac, salicylate, 2,6-dihydroxybenzoate; Ln = Dy, Er; S = water, acetonitrile, methanol) were prepared from the N,N'-dimethyl-N,N'-bis(2-hydroxy-3-formyl-5-bromobenzyl)ethylenediamine compartmental ligand (H2L). Complexes 1-6 and 9-11 consist of diphenoxido-carboxylate triply bridged compounds, which differ mainly in the carboxylate bridging ligand. It should be noted that the acidic character of the salicylic acid promotes, in the presence of methanol, the methoxylation of the H2L ligand thereby yielding a hemiacetal H3L', which is able to connect the Ln(iii) ions of two ZnLn dinuclear units forming the Zn2Ln2 tetranuclear complexes 7 and 8. All compounds display SMM behaviour in the presence of an external field with effective energy barriers (Ueff) as high as 61 K. Magneto-structural data for these complexes reveal that their SMM behaviour is not only significantly affected by the type of Ln(iii) ion but also by the carboxylate bridging ligand connecting the Zn(ii) and Ln(iii) ions. Photoluminescence properties have also been accomplished, showing that the ligands are able to sensitize lanthanide centred emissions in the visible and near-infrared regions with variable capacity. Moreover, the analysis of the luminescence decay curves reveals emission lifetimes in the range of few microsecond or hundreds of nanoseconds for Dy(iii)-based or Er(iii)-based luminophores, respectively.

Versatile organoaluminium catalysts based on heteroscorpionate ligands for the preparation of polyesters.

A series of alkyl aluminium complexes based on heteroscorpionate ligands were designed as catalysts for the ring-opening polymerisation of cyclic esters and ring-opening copolymerisation of epoxides and anhydrides. Treatment of AlX3 (X = Me, Et) with ligands bpzbeH [bpzbe = 1,1-bis(3,5-dimethylpyrazol-1-yl)-3,3-dimethyl-2-butoxide], bpzteH [bpzte = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1-para-tolylethoxide], and (R,R)-bpzmmH [(R,R)-bpzmm = (1R)-1-{(1R)-6,6-dimethyl-bicyclo[3.1.1]-2-hepten-2-yl}-2,2-bis(3,5-dimethylpyrazol-1-yl)ethoxide] for 2 hours at 0 °C afforded the mononuclear dialkyl aluminium complexes [AlMe2{κ2-bpzbe}] (1), [AlEt2{κ2-bpzbe}] (2), [AlMe2{κ2-(R,R)-bpzmm}] (3) and [AlEt2{κ2-(R,R)-bpzmm}] (4), and the dinuclear dialkyl complexes [AlMe2{κ2-bpzte}]2 (5) and [AlEt2{κ2-bpzte}]2 (6). The molecular structures of the new complexes were determined by spectroscopic methods and confirmed by X-ray crystallography. The alkyl-containing aluminium complexes can act as highly efficient single-component initiators for the ring-opening polymerisation of ε-caprolactone and l-lactide and for the ring-opening copolymerisation of cyclohexene oxide and phthalic anhydride to give a range of biodegradable polyesters.

Alkene-alkyl interconversion: an experimental and computational study of the olefin insertion and ß-hydride elimination processes.

The preparation and characterization of various alkyl, allyl or alkene Rh(iii) and Ir(iii) complexes as well as studies on the intramolecular reactions leading to transformation of one into another are reported. The silyl-hydrido-Rh(iii) complex {Rh(H)[SiMe(o-C6H4SMe)2](PPh3)}[BArF4], with a vacant coordination site, reacts with 1,5-cyclooctadiene (cod) leading to olefin insertion into the Rh-H bond and rearrangement to yield the 16e cyclooctenyl-Rh(iii) complex {Rh(η3-cyclooctenyl)[SiMe(o-C6H4SMe)2]}[BArF4] (1). This compound can be also synthesized by reaction of the 18e chloride precursor {Rh(η3-cyclooctenyl)[SiMe(o-C6H4SMe)2]Cl} with NaBArF4. The reaction of the thioether-silane SiMeH(o-C6H4SMe)2 with [Rh(nbd)Cl]2 (nbd = norbornadiene) leads to {Rh(σ-ntyl)[SiMe(o-C6H4SMe)2]Cl} (ntyl = nortricyclyl) (2). The abstraction of chloride from this neutral 16e ntyl-Rh(iii) complex with NaBArF4 results in the unusual isomerization of σ-nortricyclyl into σ,π-norbornenyl forming the 16e and cationic {Rh(σ,π-nbyl)[SiMe(o-C6H4SMe)2][BArF4] (nbyl = norbornenyl)} compound 3. Coordinatively saturated {Ir(η3-cyclooctenyl)[SiMe(o-C6H4SMe)2]Cl} (4) has been synthesized by the reaction of [Ir(cod)Cl]2 with SiMeH(o-C6H4SMe)2. The reaction of 4 with NaBArF4 led to the formation of the unsaturated and cationic Ir(iii) compound {Ir(η3-cyclooctenyl)[SiMe(o-C6H4SMe)2]}[BArF4] (5). Compound 5 shows low stability in solution and undergoes successive ß-hydride elimination and olefin insertion steps, which were elucidated by DFT calculations, to form 18e {Ir(H)[SiMe(o-C6H4SMe)2](η4-cod)}[BArF4] (6).

In vitro leishmanicidal and trypanocidal evaluation and magnetic properties of 7-amino-1,2,4-triazolo[1,5-a]pyrimidine Cu(II) complexes.

Two triazolopyrimidine complexes have been obtained from reaction between 7-amino-1,2,4-triazolo[1,5-a]pyrimidine (7atp) and Cu (II) salts. Crystal structures of [Cu2(µ-7atp)4Cl2]Cl2·4H2O (1) and [Cu2(µ-7atp)4(H2O)2](NO3)4·H2O (2) have been studied by X-ray diffraction methods and characterized by spectroscopic and thermal analysis. Magnetic studies of these dinuclear complexes have revealed the existence of moderate antiferromagnetic interactions between the copper ions, with J values of -91.2 and -96.1cm-1 respectively. It must be highlighted that the antiparasitic activity of these new complexes has been studied in vitro against three different strains of leishmania spp. and Trypanosoma cruzi, showing a higher efficacy than the 7atp ligand and the reference commercial drugs.

Antiparasitic activity against trypanosomatid diseases and novel metal complexes derived from the first time characterized 5-phenyl-1,2,4-triazolo[1,5-a]pyrimidi-7(4H)-one.

A serie of isostructural complexes with general formula [M(ftpO)2(H2O)4] have been obtained from reaction between the first time characterized triazolopyrimidine derivative 5-phenyl-1,2,4-triazolo[1,5-a]pyrimidi-7(4H)-one (HftpO) (1) and first row transition nitrates (M=Cu (2), Co (3), Ni (4) and Zn (5)). A copper complex with formula [Cu(HftpO)2(NO3)2(H2O)2]·H2O (6) was also isolated. HftpO and their metal complexes have been characterized by spectroscopic and thermal analysis and their crystal structures have been solved by X-ray diffraction methods. The isostructural compounds are mononuclear complexes where the triazolopyrimidine ligand acts as monodentate ligand through N3 nitrogen position. The crystal structure of these novel bis-5-phenyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one-tetraaquo metal complexes offers an excellent opportunity at these complexes to acts as potential building blocks. Also, the antiparasitic activity of HftpO ligand against different leishmania and trypanosome strains has been studied.

A pentacoordinated norbornenyl-acyl-rhodium(iii) complex as a likely intermediate in the catalytic hydroacylation of norbornadiene.

[RhCl(NCO)(nbyl)(PR3)] (nbyl = σ-norbornenyl; NCO = quinoline-8-acyl; R = p-F-C6H4) (1) has been synthesized by the reaction of [Rh(nbd)Cl]2 (nbd = norbornadiene) with 2 equivalents of NCHO (quinoline-8-carbaldehyde) and 2 equivalents of PR3. Compound 1 has been fully characterized in solution and also in the solid state by X-ray diffraction. Compound 1 shows low stability in solution and undergoes slow ring closure isomerization to [RhCl(NCO)(ntyl)(PR3)] (ntyl = σ-nortricyclyl) (2) after 12 hours. Reaction of 1 with an extra equivalent of aldehyde (NCHO) and PR3 led to the formation of [RhCl(H)(NCO)(PR3)2] (3) and an equivalent of ketone, which is a hydroacylation product. The catalytic activity of 3 in the hydroacylation of nbd with NCHO is reported as well as the catalytic activity of compound 1. Compounds 1 and 3 are proposed as intermediate species in the catalytic hydroacylation of norbornadiene with NCHO.

First examples of metal-organic frameworks with the novel 3,3'-(1,2,4,5-tetrazine-3,6-diyl)dibenzoic spacer. Luminescence and adsorption properties.

We report the synthesis of a novel ligand, 3,3'-(1,2,4,5-tetrazine-3,6-diyl)dibenzoic acid (1). In this fragment, we have introduced two carboxylate groups with the aim of using this ligand as a linker to construct three-dimensional metal-organic frameworks (MOFs). We have been successful in the formation of zinc (2) and lanthanum (3) MOFs. The zinc compound is a two-dimensional structure, while the lanthanum material is a three-dimensional MOF with interesting channels. We include the luminescence and adsorption studies of these materials. Moreover, we have evaluated the in vitro toxicity of this novel ligand, concluding that it can be considered negligible.

Development of polymeric sensing films based on a tridentate bis(phosphinic amide)-phosphine oxide for detecting europium(III) in water.

A novel europium(III) membrane luminescence sensor based on a tridentate bis(phosphinic amide)-phosphine oxide, PhPO(C(6)H(4)POPhN(CH(CH(3))(2))(2))(2) (1), is described. The new luminescent complex, [Eu(1)(2)]Cl(3)2, which is formed between europium(III) and ligand 1 and has a 1 : 2 stoichiometry, has been evaluated in solution. It has the excellent spectroscopic and chemical characteristics that make it appropriate for sensing film applications. All the parameters (polymer, plasticizer, ligand and ionic additive) that can affect the sensitivity and selectivity of the membrane sensor and instrumental conditions have been carefully optimized. The best sensing response (λ(exc) = 229.04 nm, λ(em) = 616.02 nm) was observed for 33.4 : 65.1 : 1.5 (%, w/w) PVC : DOS : 1. The sensing film shows a good response time (10 min) and a very good selectivity toward europium(III) with respect to other lanthanides(III) ions, such as La, Sm, Tb and Yb. The newly-developed sensing film has a linear range from 1.6 × 10(-7) to 5.0 × 10(-6) mol L(-1) for Eu ions with a very low detection limit (4.8 × 10(-8) mol L(-1)) and good sensitivity (9.41 × 10(-7) a.u. mol(-1) L(-1)) to europium. Complexes of [Eu(1)(2)]Cl(3) (2) and [Eu(1)]Cl(3) (4) were isolated by mixing ligand 1 with Eu(Cl(3))·6H(2)O in acetonitrile at room temperature in ligand : metal molar ratios of 1 : 2 and 1 : 1, respectively. The 1 : 1 derivative is the product of thermodynamic control when a molar ratio of ligand to europium salt of 1 : 1 is used. The new compounds have been characterized in both the solid form (IR, MS-TOF, elemental analysis, TGA and X-ray diffraction) and in solution (multinuclear magnetic resonance). In both europium complexes, the ligand acts as a tridentate chelate. Thermogravimetric (TG) studies demonstrated that neither complex 2 or 4 possess any water molecules directly bound to the lanthanide metal, which corroborates the X-ray structure. The investigation of the solution behaviour of the Y(III) complexes with pulsed gradient spin-echo (PGSE) NMR diffusion measurements showed that average structures with 1 : 1 and 1 : 2 stoichiometries are retained in acetonitrile solutions.

Theoretical and experimental study of the effectiveness of the 5-pyrimidyl-tetrazolate bridging ligand in mediating magnetic exchange interactions.

The 5-pyrimidyl-tetrazolate anion (pmtz) has six basic nitrogen atoms and, consequently, can exhibit a variety of bridging coordination modes. This ligand reacts with either copper(II) and nickel(II) ions in the presence of bi- and tridentate amines to afford the following pmtz-bridged complexes: [Cu(4)(µ-pmtz)(4)(tmda)(4)](ClO(4))(4) (1) (tmda = N,N,N',N'-tetramethylethylenediamine), [Cu(2)(µ-pmtz)(tren)(2)](ClO(4))(3) (2) (tren = tris(2-aminoethyl)amine), [Ni(2)(µ-pmtz)(tren)(2)](ClO(4))(3) (3), and [Ni(2)(µ-pmtz)(2)(ampa)(2)](n)(SCN)(2n) (ampa = bis(3-aminopropyl)amine) (4). The structure and bridging coordination mode of these complexes depend on the stereoelectronic preferences of the metal ion and the coordination properties of the polyamine (denticity and relative disposition of the donor atoms). Thus, complex 1 is a square tetranuclear compound where the ligand adopts an asymmetric k(2)N(1),N(7):k(2)N(4),N(11) bis(chelating)/bridging mode. Complexes 2 and 3 are dinuclear species. In the former the pmtz exhibits a novel k-N(1):k-N(4) imidazolyl/bridging mode whereas the latter shows a symmetric k(2)N(1),N(7):k(2)N(4),N(11) bis(chelating)/bridging mode. Complex 4 exhibits, however, a linear chain structure where the pmtz ligand connects neighboring nickel(II) atoms by using a tridentate k(2)N(1),N(7):kN(3) chelating/bridging mode. Variable-temperature magnetic susceptibility studies reveal that complexes 1-4 show weak to moderate antiferromagnetic (AF) coupling between the metal ions through the pmtz ligand with J = -14.1 cm(-1) for 1, J = -31.1 cm(-1) for 2, J = -4.09 cm(-1) for 3, and J = -8.7 cm(-1) for 4. The magneto-structural results, as well as DFT theoretical calculations carried out on the experimental geometries and model complexes, demonstrate, first, that the magnitude of the AF interaction observed for imidazolyl pmtz-bridged complexes mainly depends on the Cu-N-C angle (the greater the Cu-N-C angle, the stronger is the AF interaction) and, second, that the tridentate chelating/bridging mode is more effective in mediating AF exchange interactions than the bis(chelating)/bridging or imidazolyl/bridging modes in pmtz-bridged complexes.

Anion influence on the structure and magnetic properties of a series of multidimensional pyrimidine-2-carboxylato-bridged copper(II) complexes.

Seven new polynuclear copper(II) complexes of formula [Cu(mu-pymca)2] (1) (pymca(-) = pyrimidine-2-carboxylato), [Cu(mu-pymca)Br] (2), [Cu(mu-pymca)Cl] (3), [Cu(mu-pymca)(SCN)(H2O)] x 4 H2O (4), [Cu(mu-pymca)N3] (5), [Cu2(mu1,5-dca)2(pymca)2] (6) (dca = dicyanamide), and K{[mu-Au(CN)2]2[(Cu(NH3)2)2(mu-pymca)]}[Au(CN)2]2 (7) have been synthesized by reactions of K-pymca with copper(II) ions in the presence of different counteranions. Compound 1 is a linear neutral chain with a carboxylato bridging ligand in a syn-anti coordination mode, whereas complexes 2 and 3 consist of cationic linear chains with cis and trans bis(chelating) pymca bridging ligands. Complex 4 adopts a helical pymca-bridged chain structure. In complex 5, zigzag pymca-bridged chains are connected by double end-on azide bridging ligands to afford a unique honeycomb layer structure. Complex 6 is a centrosymmetric dinuclear system with double mu 1,5-dicyanamide bridging ligands and pymca end-cap ligands. Complex 7 is made of pymca-bridged dinuclear [Cu(NH3)2(mu-pymca)Cu(NH3)2](3+) units connected by [Au(CN)2](-) anions to four other dinuclear units, giving rise to cationic (4,4) rectangular nets, which are linked by aurophilic interactions to afford a singular 3D network. Variable-temperature magnetic susceptibility measurements show that complex 1 exhibits a very weak antiferromagnetic coupling through the syn-anti (equatorial-axial) carboxylate bridge (J = -0.57 cm(-1)), whereas complexes 2-4 and 7 exhibit weak to strong antiferromagnetic couplings through the bis(chelating) pymca bridging ligand J = -17.5-276.1 cm(-1)). Quantum Monte Carlo methods have been used to analyze the experimental magnetic data for 5, leading to an antiferromagnetic coupling (J = -34 cm(-1)) through the pymca ligand and to a ferromagnetic coupling (J = 71 cm(-1)) through the azide bridging ligands. Complex 6 exhibits a very weak antiferromagnetic coupling through the dicyanamide bridging ligands (J = -5.1 cm(-1)). The magnitudes of the magnetic couplings in complexes 2-5 have been explained on the basis of the overlapping between magnetic orbitals and DFT theoretical calculations.

A rational design by hydrothermal methods of a tetrazolate-bridged bimetallic spin-canted antiferromagnet. Synthesis, X-ray structure and magnetic properties of [CoNi(pmtz)4] (Hpmtz- = 5-(pyrimidyl)tetrazole).

The bimetallic complex [CoNi(pmzt)4] (pmtz- = 5-(pyrimidyl)tetrazolate ligand) has been prepared by hydrothermal treatment of an equimolecular mixture of the mononuclear complexes[Co(pmtz)2(H2O)2] and [Ni(pmtz)2(H2O)2]. The structure of [CoNi(pmzt)4] consists of (4,4) square-grid-like sheets, in which Co(II) and Ni(II) metal ions are connected by pmtz(-) bridging ligands. This compound is a spin-canted antiferromagnet (weak ferromagnet) with Tc = 18 K. Although Co(II) and Ni(II) ions have different spin values, the spin-canted structure can be formed because of the accidental compensation of their magnetic moments. Both magnetic anisotropy and antisymmetric exchange interaction promote the spin canting of the compensated magnetic moments in the 3D antiferromagnetic phase. On passing from the homometallic complex, [Co2(pmzt)4], which is also a spin-canted antiferromagnet with Tc = 15 K, to the bimetallic complex, [CoNi(pmzt)4], Tc increases and the hysteresis parameters, remnant magnetization (Mr) and critical field (Hc), decrease. The increase in Tc may be a consequence of the increase of the JCoNi, whereas the decrease in Mr and Hc is probably due to the presence in [CoNi(pmzt)4] of a lower content of the highly anisotropic Co(II) ion.

Synthesis, X-ray structures and luminescence properties of three multidimensional metal-organic frameworks incorporating the versatile 5-(pyrimidyl)tetrazolato bridging ligand.

The hydrated sodium salt of the novel and versatile 5-(pyrimidyl)tetrazolato ligand (pmtz(-)), Na(pmtz).H(2)O (1), has been prepared in very mild conditions from 2-cyanopyrimidine and NaN(3). Two coordination polymers [Cd(pmtz)(2)]n (2)and [Cd(pmtz)(micro-Cl)(0.5)(micro-N(3))(0.5)(H(2)O)](n)(3), , have been synthesized from (1)under conventional or hydrothermal conditions, respectively, and fully characterized by single-crystal or powder X-ray diffraction methods. Compounds and consist of mono-dimensional polymeric chains, further stabilized by interchain pi-pi stacking and hydrogen bond interactions. Compound , containing octacoordinated Cd ions of crystallographic D(2) symmetry, exhibits neutral (4, 4) layers formed by square units of the metallacalix[4]arene type in 1,3-alternate conformation. Species , and display intense, room temperature, photoluminescence in the solid state.

[Zn(n)(polyox)(pmtz)n]: the first polyoxalate-containing coordination polymer from an unforeseen chemical rearrangement of 5-pyrimidyl-tetrazole under hydrothermal conditions.

The compound [Zn(2)(polyox)(pmtz)(2)], which has been prepared by the hydrothermal reaction of ZnCl(2) and Napmtz (5-pyrimidyl-tetrazolate), exhibits a unique 2D network with (6,3) topology, in which Zn(II) ions are connected by pmtz- and polyoxalate-bridging ligands (generated in situ from the breaking of the pmzt(-) ligand). This is the first structural report on a polyoxalate species.