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R
Rosa, V., S. A. Carabineiro, T. Aviles, P. T. Gomes, R. Welter, J. M. Campos, and M. R. Ribeiro. "Synthesis, characterisation and solid state structures of alpha-diimine cobalt(II) complexes: Ethylene polymerisation tests." J Organomet Chem. 693 (2008): 769-775. AbstractWebsite

A series of cobalt(II) compounds of the type [CoX2(alpha-diimine)] were synthesised by direct reaction of anhydrous CoCl2 or CoI2 and the corresponding alpha-diimine ligand, in CH2Cl2: [CoI2(o,o',p-Me3C6H2-DAB)] ( 1), [ CoI2(o,o'-(Pr2C6H3)-Pr-i-DAB)] ( 2), ( where Ar-DAB = 1,4-bis(aryl)-2,3-dimethyl-1,4-diaza-1,3-butadiene), and [CoCl2(o,o',p-Me3C6H2- BIAN)] (3), [CoCl2(o,o'- (Pr2C6H3)-Pr-i-BIAN)] (4), and [CoI2(o,o'-(Pr2C6H3)-Pr-i-BIAN)] (5) (where Ar-BIAN = bis(aryl) acenaphthenequinonediimine). All compounds were characterised by elemental analyses, IR, mass spectrometry, and X-ray diffraction whenever possible. The crystal structures of compounds 2-4 showed, in all cases, distorted tetrahedral geometries about the Co, built by two halogen atoms and two nitrogen atoms of the alpha-diimine ligand. Compounds 3 and 4, as well as [ CoCl2(o,o',p-Me3C6H2-DAB)] (1a), and [ CoCl2( o,o'- (Pr2C6H3)-Pr-i- DAB)] (2a), were activated by methylaluminoxane (MAO) and tested as catalysts for ethylene polymerisation, showing low catalytic activities. Selected polyethylene ( PE) samples were characterised by H-1 and C-13 NMR and FT-IR spectroscopies, and by differential scanning calorimetry (DSC), revealing branching microstructures (2.5-5.5%). (c) 2007 Elsevier B. V. All rights reserved.

Romain, Charles, Vitor Rosa, Christophe Fliedel, Frederic Bier, Frederic Hild, Richard Welter, Samuel Dagorne, and Teresa Aviles. "{Highly active zinc alkyl cations for the controlled and immortal ring-opening polymerization of epsilon-caprolactone}." {DALTON TRANSACTIONS}. {41} (2012): {3377-3379}. Abstract

{Zinc alkyl cations supported by N,N-BIAN-type bidentate ligands were found to be highly active in the immortal ROP of epsilon-caprolactone to yield narrowly disperse and chain length-controlled poly(epsilon-caprolactone), whether in solution or bulk polymerization conditions.}

P
Pinto, P., M. J. Calhorda, V. Felix, T. Aviles, and M. G. B. Drew. "Syntheses and crystal structures of polynuclear Cu(I) complexes containing the 1,1 '-bis(diphenylphosphino)-ferrocene ligand." Monatsh Chem. 131 (2000): 1253-1265. AbstractWebsite

The reaction between [Cu(NCMe)(4)][PF6] and 1,1'-bis-(diphenylphosphino)-ferrocene (dppf) in several ratios, solvents, and conditions led to the synthesis and structural characterization of the Cu(I) complexes [Cu(dppf)(Odppf)] [PF6] (1), [(dppf)Cu(mu -dppf)Cu(dppf)][PF6](2) (2), and [(dppf)Cu(mu -Cl)(2)Cu(dppf)] (3). Although 1 and the cation in 2 were known, the first was structurally characterized for the first time, exhibiting a significant asymmetry in the coordination sphere of Cu(I)) owing to the presence of oxygen. In 2, the PF6- anion led to an interesting crystal packing with large open channels containing water. Finally, DFT calculations on a model of 3 showed that its HOMO exhibits, besides Fe, a significant Cu and Cl character, which is reflected in its electrochemical properties.

Pedras, B., H. M. Santos, L. Fernandes, B. Covelo, A. Tamayo, E. Bertolo, J. L. Capelo, T. Aviles, and C. Lodeiro. "Sensing metal ions with two new azomethine-thiophene pincer ligands (NSN): Fluorescence and MALDI-TOF-MS applications." Inorg Chem Commun. 10 (2007): 925-929. AbstractWebsite

The two new pincer azomethine-thiophene ligands (N,NE',N,NE')-N,N'-(thiophene-2,5-diylbis(methan-1-yl-1-ylidene))bis(naphathalen-2-ylmethanamine) (L1) and (E)-(4,6-dihydropyren-1-yl)-N-((5-((E)-(pyren-1-ylmethylimino)ethyl)thiophen-2-yl)methylene)methanamine (L2), their absorption, fluorescence and MALDI-TOF-MS spectroscopic studies are described. The two systems synthesised combine the emissive probes pyrene and naphthyl with the good chelating properties of a tridentate SN2 donor-set from a thiophene Schiff-base ligand. Both ligands gave analytically pure solid complexes with Ni(II) and Pd(II) salts. The bichromophoric pyrene derivative L2 presents two emission bands in solution, one corresponding to the monomer species and a red-shifted band attributable to the intramolecular excimer. Ni(II) and Pd(II) complexation affects the conformation in solution, increasing the monomer emission at the expense of the excimer band; this effect could be explored in metal ion sensing. System L1 behaves as a non emissive probe. In situ complexation reactions followed by MALDI-TOF-MS spectrometry without matrix support have also been performed; these experiments show that L1 could be a potential chemosensor for Ni(II) and Pd(11). (c) 2007 Elsevier B.V. All rights reserved.

Pedras, B., E. Oliveira, H. Santos, L. Rodriguez, R. Crehuet, T. Aviles, J. L. Capelo, and C. Lodeiro. "A new tripodal poly-imine indole-containing ligand: Synthesis, complexation, spectroscopic and theoretical studies." Inorg Chim Acta. 362 (2009): 2627-2635. AbstractWebsite

A novel flexible tripodal ligand derived from 3-methylindole, ("InTREN" L), and its mononuclear Zn(II), Cu(II), Ni(II), Hg(II) and Pd(II) complexes are described. All compounds gave analytically pure solid samples. Characterisation of the compounds was accomplished by (1)H NMR, IR and absorption spectroscopies, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and elemental analysis and their geometry optimized using density functional theory (DFT).Time-dependent-density functional theory (TD-DFT) calculations have been used to assign the lowest energy absorption bands of the free ligand and the Zn(II) complex. The system is a very good candidate for in situ recognition/coordination effects by MALDI-TOF-MS spectrometry and absorption spectroscopy. The presence of three indole groups in InTREN opens up the possibility to synthesize new three-dimensional self-assembly supramolecular structures. (C) 2008 Elsevier B.V. All rights reserved.

M
Montilla, F., E. Clara, T. Aviles, T. Casimiro, A. A. Ricardo, and M. N. da Ponte. "Transition-metal-mediated activation of arylisocyanates in supercritical carbon dioxide." J Organomet Chem. 626 (2001): 227-232. AbstractWebsite

The reactivity of arylisocyanates in supercritical carbon dioxide (scCO(2)) was studied using the easily available complexes CpCo(CO)(2), CpCoPPh3Me2 and Ni(cod)(2) as catalysts. A study of the solubility of the catalysts in scCO(2) was undertaken in all cases. The complex CpCo(CO)(2) is very soluble, 1.7 x 10(-1) mol kg(-1), while CpCoPPh3Me2 has a lower solubility, 7.2 x 10(-3) mol kg(-1), and Ni(cod)(2) is insoluble in scCO(2). For comparison purposes, the reactions were performed in parallel in scCO(2), using toluene as a solvent and just with the neat liquid arylisocyanate. Reactions in scCO(2) either do not take place at all, when CpCo(CO), is used as catalyst, or occur with low yields affording the trimer of the corresponding arylisocyanate when CpCoPPh3Me2 or Ni(cod)(2) act as catalysts. No incorporation of CO2 into the organic substrate was observed. Better conversions to triarylisocyanate were obtained when the reactions were performed by direct mixture of the liquid arylisocyanate ArNCO (Ar = Ph, p-CH3C6H4, p-CH3OC6H4) and the catalyst. Using toluene as a solvent, the yields of the trimers were lower than those obtained in neat arylisocyanate, and in some cases they were not formed at all. For instance in the reaction of CpCo(CO), and tolylisocyanate either under stoichiometric or catalytic conditions the trimer is not obtained, instead the compound H2R3N3C2O2 (R = CH3C6H4), was isolated in low yield. In the reaction of Ni(cod)(2)/PPh3 with phenylisocyanate, the trimer was formed but in low yield. The lower yields of the trimers observed when the reactions were performed in scCO(2) or in toluene, compared to that observed in neat arylisocyanates, indicates that the decrease in reactivity is due to a decrease in concentration. (C) 2001 Elsevier Science B.V. All rights reserved.

Montilla, F., V. Rosa, C. Prevett, T. Aviles, M. N. da Ponte, D. Masi, and C. Mealli. "Trimethylsilyl-substituted ligands as solubilizers of metal complexes in supercritical carbon dioxide." Dalton T (2003): 2170-2176. AbstractWebsite

The SiMe3 group (TMS), introduced as a substituent at the cyclopentadienyl ligand, is found to magnify the solubility of the corresponding metal complexes in supercritical carbon dioxide (scCO(2)). This is verified from comparative solubility measurements of the species (eta(5)-Me-3 SiC5H4)MoO2 Cl, 1a, (eta(5)-Me3SiC5H4)(2)ZrCl2, 2a, and (eta(5)-Me3SiC5H4)Co(CO)I-2.0.5(I-2), 3a (newly synthesised), and of their unsubstituted precursors 1b-3b, respectively. In spite of the increased solubility, the chemical, structural and reactivity properties of the TMS derivatives are scarcely affected. Confirmation comes from a detailed study of the cobalt complex 3a that includes X-ray structural determination. The geometry is most similar to that of the precursor 3b while an apparently different Co-CO interaction is observed in the carboxylated analogue [(eta(5)-PhCH2CO2C5H4)Co(CO) I-2, 3c]. The problem is computationally tackled by using the DFT B3LYP method. The optimised geometries of the simplified models of 3a-3c are all very similar. In particular, the computed stretching frequency of the unique CO ligand is consistent with the insignificant influence of the TMS group while it suggests a reduced amount of metal back-donation in 3c. It is inferred that the TMS complexes 1a-3a, while having higher solubility in scCO2, maintain almost unaltered the electronic and chemical features of their parent compounds. In particular, the role of 1a-3a as catalysts, that is well documented for homogeneous solutions, remains unaltered in the very different scCO(2) environment. The assumption is experimentally validated for 1a by performing with the latter two classic catalytic processes. The first process is the oxidation of PPh3 that is achieved by using molecular oxygen as an oxidant. The second example concerns the epoxidation of cyclohexene achieved in presence of tert-butyl hydroperoxide (TBHP).

Montilla, F., T. Aviles, T. Casimiro, A. A. Ricardo, and M. N. da Ponte. "CPCO(CO)(2)-catalysed cyclotrimerisation of alkynes in supercritical carbon dioxide." J Organomet Chem. 632 (2001): 113-118. AbstractWebsite

The reactivity of mono-substituted HC=CR (R =Ph. a; CH2OH, b; CH2CH2CH2CH3, c) and di-substituted RC=CR (R = CH2CH3, d; CO2CH3, e; Ph. f) acetylenes was studied in supercritical carbon dioxide (scCO(2)) using the easily available complex CpCo(CO)(2) as catalyst. The reaction of phenylacetylene produced a mixture of the isomeric cyclotrimers 1,3,5- (2a) and 1.2,4-triphenylbenzene (2a '). in a 1:5 ratio, and traces of cobaltcyclopentadienone complexes CPCO(eta (4)-C4H2[Ph](2)CO) (6a, mixture of isomers). The possible product formed by the incorporation of CO, to alkynes, i.e. diphenylpyrone (7a) was not observed. The reaction of the cobaltacyclopentadiene complex CpCo(1.4-sigma -C-4[Ph](4))(PPh)(3) (8f), in scCO(2), was performed. No insertion of CO2 into the Co-C a-bond to form tetraphenylpyrone (7f) by reductive elimination was observed, instead the cobaItcyclobutadiene Complex CpCo(eta (4)-C-4[Ph](4)) (9f) was formed. In the reactions with other alkynes, lower yields were obtained in general, except in the cyclotrimerisation of the highly activated alkyne, propargyl alcohol (b). Reaction of the non-activated alkynes, 1-hexyne (c) and 3-hexyne (d), produced complex mixtures of cobalt complexes in low yield in which the alkyne was coordinated to cobalt. Finally, the highly hindered diphenylacetylene (f) gave a mixture of the known Complexes CpCo(eta (4)-C-4[Ph](4)) (9f) and CpCo(eta (4)- C-4[Ph](4)CO) (6f) in agreement with the results observed in conventional organic solvents. (C) 2001 Elsevier Science B.V, All rights reserved.

Montilla, F., A. Galindo, V. Rosa, and T. Aviles. "Effect of trimethylsilyl substitution on the chemical properties of triarylphosphines and their corresponding metal-complexes: Solubilising effect in supercritical carbon dioxide." Dalton T (2004): 2588-2592. AbstractWebsite

The donor strengths of the following triarylphosphine ligands P(Ar)(2)(Ar') (Ar = Ar' = 4-Me3SiC6H4, 1b; 4-Me3CC6H4, 1d; 4-F3CC6H4, 1e; Ar = C6H5, Ar' = 4-Me3SiC6H4, 1c) have been evaluated experimentally and theoretically. The measurements of the J(P-Se) coupling constants of the corresponding synthesised selenides Se=P(Ar)(2)(Ar'), 2b, c and the DFT calculation of the energies of the phosphine lone-pair ( HOMO) reveal insignificant influence on the electronic properties of the substituted phosphines when the trimethylsilyl group is attached to the aryl ring, in marked contrast to the strong electronic effect of the trifluoromethyl group. These triarylphosphine ligands P(Ar)(2)(Ar') reacted with (eta(5)-C5H5)Co(CO)(2), (eta(5)-C5H5)Co(CO)I-2 or PdCl2 to yield the new compounds (eta(5)-C5H5)Co(CO)[P(Ar)(2)(Ar')], 3b, d; (eta(5)-C5H5)COI[P(Ar)(2)(Ar')], 4b-e; and PdCl2[P(Ar)(2)(Ar')](2), 5b, c, respectively. These complexes have been characterized and their spectroscopic properties compared with those reported for the known triphenylphosphine complexes. Again, the contrast of the P-31 NMR and C-13 NMR chemical shifts or C-O or M-Cl stretching frequencies, when applied, does not show an important electronic effect on the metal complex of the trimethylsilyl substituted phosphines with respect to P(C6H5)(3) derivatives. Solubility measurements of complexes 3a and 3b in scCO(2) were performed. We conclude that Me3Si groups on the triarylphosphine improve the solubility of the corresponding metal complex in scCO(2).

Maiti, Biplab K., Teresa Aviles, Manolis Matzapetakis, Isabel Moura, Sofia R. Pauleta, and Jose J. G. Moura. "{Synthesis of {[}MoS4](2-)-M (M=Cu and Cd) Clusters: Potential NMR Spectroscopic Structural Probes for the Orange Protein}." {EUROPEAN JOURNAL OF INORGANIC CHEMISTRY} (2012): {4159-4166}. Abstract

{Two synthetic strategies of tetrathiomolybdate-metal clusters with the potential to be used as NMR structural probes for the location of the metal cofactor in the orange protein (ORP) are described. The first strategy is based on the substitution reaction in which small organic ligands bind directly to the metal centre in a molybdenumcopper hetero-dinuclear cluster. Interaction between {[}PPh4]2{[}MoS4CuCl] and either aliphatic {[}beta-mercaptoethanol (b-me)] or aromatic {[}o-aminobenzenethiol (abt)] thiols in the presence of a strong base resulted in the formation of {[}Ph4P]2{[}S2MoS2Cu(b-me)] (1a) and {[}Et4N]2{[}S2MoS2Cu(abt)]center dot H2O center dot 0.25DMF (1b), which can be used to obtain intermolecular NOEs. The compound 1a readily hydrolyzed to {[}Ph4P]2{[}OSMoS2Cu(b-me)] (1ahydro) in contact with a protic solvent. The second strategy consisted of the incorporation of cadmium into tetrathiomolybdate ({[}MoS4]2), which gives rise to the trinuclear cluster compound {[}PPh4]2{[}(MoS4)2Cd] (2). All clusters were characterized spectroscopically and their structure determined by X-ray diffraction. The NMR spectroscopic data are consistent with the formation of a complex with a 1:1 ratio of \{MoS4Cu\} and thiol. The 113Cd NMR chemical shift of compound 2 is consistent with the cadmium having a tetrahedral geometry and coordinated by four sulfur ligands. The tetraphenylphosphonium cation in compound 1a was replaced by a tetramethylammonium countercation originating in the water-soluble compound {[}Me4N-1a]. Solubility in aqueous buffers is a requirement for incorporating this cluster into apo-ORP. These compounds will be used to identify the exact location of the ORP heterometallic cluster using NMR methodologies.}