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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.

New cationic mono-cyclopentadienyl complexes of Co(III) containing mono or bidentate nitrogen donor ligands of general formula [Co(eta (5)-C5H5)(PPh3)L-2][BF4](2) (L = NC-CH3, 2, and NC = Ph, 3) or [Co(eta (5)-C5H5)(PPh3)(L-L)[BF4](2), [L-L = 2,2 ' -bisimidazole (H(2)biim) (4) and dipyridylamine [HN(NC5H5)(2)] (5) have been synthesised by the stoichiometric reaction of the Co(III) complex Co(eta (5)-C5H5)(PPh3)I-2 (1), with Ag[BF4] and the appropriate ligand in CH2Cl2. Under the same conditions and using;trans-azobenzene as a ligand, an orthometalation reaction took placet giving the new compound [Co(eta (5)-C5H5)(PPh3)(kappa -C,kappa -N-C6H4N=NPh)][BF4] (6) in high yield. The structural characterisation of compounds 4 and 6, and of the starting compound Co(eta (5)-C5H5)(PPh3)I-2 (1) was done by single-crystal X-ray diffraction studies. DFT calculations (ADF program) were performed in order to understand the orthometallation reaction. (C) 2001 Elsevier Science B.V. All rights reserved.

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.

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.

Rhodium complexes modified by simple trialkylphosphines can be used to carry out homogeneous hydroformylation in supercritical carbon dioxide (scCO(2)). The catalyst derived from PEt3 is more active and slightly more selective for the linear products in scCO2 than in toluene, and under the same reaction conditions [100degreesC, 40 bar of CO/H-2 (1:1)] P(OPri)(3) is also an effective ligand giving good catalyst solubility and activity. Other ligands such as PPh3, POct(3), PCy3, and P(4-C6H4But)(3) are less effective because of the low solubility of their rhodium complexes in scCO(2). P(4-C6H4SiMe3)(n) Ph3-n (n = 3 or 1) and P(OPh)(3) impart activity despite their complexes only being poorly soluble in scCO(2). Under subcritical conditions, using PEt3 as the ligand, C7-alcohols from hydrogenation of the first formed aldehydes are the main products whilst above a total pressure of 200 bar, where the solution remains supercritical (monophasic) throughout the reaction, aldehydes are obtained with 97% selectivity. High pressure IR studies in scCO(2) using PEt3 as the ligand are reported.

The new compound [Co(eta(5)-C5H5)(dppf-P,P')I]I, 1, was synthesised by the stoichiometric reaction of the Co(III) complex [Co(eta(5)-C5H5)(CO)I-2], 2, with 1,1'-bis(diphenylphosphino)ferrocene (dppf) in CH2Cl2, and was characterised by multinuclear NMR spectroscopy. Exposure to air of THF or CH2Cl2 solutions of compound 1 gave, in an unexpected way, a polymeric chain comprising bridging 1,1'-bis(oxodiphenylphosphoranyl) ferrocene (dppfO(2)) joining tetrahedral Co(II) units [CoI2(mu-dppfO(2))](n), 3. Attempts to obtain the polymeric chain 3 by the direct reaction of dppfO(2) with CoI2, in CH2Cl2, gave instead the monomeric compound [CoI2(dppfO(2))], 4, in which dppfO2 is coordinated in a chelating mode. The structural characterisation of compounds 2, 3, and 4 was carried out by single crystal X-ray diffraction studies. The magnetic behaviour of [CoI2(dppfO(2))] and [CoI2(mu-dppfO(2))](n) was studied, and the results are consistent with tetrahedral S = 3/2 Co-II, possessing a (4)A(2) ground state, and S = 0 Fe-II. In these compounds, Co-II negative zero field splittings were determined from an analysis of the magnetic susceptibility temperature dependence, with D/k = -13 and -14 K for CoI2(dppfO(2)) and [CoI2(mu-dppfO(2))](n), respectively. DFT calculations were performed in order to understand the electronic structure of [Co(eta(5)-C5H5)(dppf-P,P')I]I, 1, as well as that of the paramagnetic specie [CoI2(dppfO(2))], 4. The [CoI2(mu-dppfO(2))](n) chain was also analysed and found to behave very similarly to the monomeric iodine derivative 4. The calculations showed the unpaired electrons to be localized on the Co(II) centre in all these species. The rather complicated electrochemical behaviour exhibited by the dppf complex [Co-III(eta(5)-C5H5)(dppf-P,P')I]I and by [Co(dppfO(2))I-2] is discussed.

The phase behaviour of the binary mixture of carbon dioxide and the cobalt complex dicarbonyl(eta(5)-cyclopentadienyl)-cobalt, CPCo(CO)(2), has been investigated. This organometallic compound is one of the most effective catalysts of cyclotrimerization reactions of arylisocyanates and alkynes. Vapour-liquid equilibrium (VLE) measurements were undertaken in a static analytical apparatus at 313.15, 323.15 and 363.15 K at pressures up to 15 MPa. p, T isopleths were measured by a synthetic method in a Cailletet apparatus. Nine different compositions ranging from 17.56 to 94.23 mol% of CO2 were measured up to 15 MPa. Modelling with the Peng-Robinson equation of state (PR EOS) gave reasonable results in the correlation of the experimental phase equilibrium compositions using two temperature-dependent interaction parameters. (C) 2003 Elsevier B.V. All rights reserved.

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.

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.