Teresa Avilés

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.

The coordination properties of the beta-keto phosphine ligands R(2)PCH(2)C(O)Ph (HL(1), R = i-Pr; HL(2), R = Ph), of the new acetamide-derived phosphine ligand (i-Pr)(2)PNHC(O) Me (HL(3)) and of Ph(2)PNHC(O) Me (HL(4)) have been examined towards Ni(II) complexes. Comparisons are made between systems in which the PCH(2) function of the ketophosphine has been replaced with an isoelectronic PNH group in amide-derived ligands, or the PCH functionality of phosphinoenolates with a PN group in phosphinoiminolate complexes. Furthermore, ligands HL(2) and HL(4) reacted with [(eta(5)-C(5)H(5))CoI(2)(CO)] to afford the phosphine mono-adducts [(eta(5)-C(5)H(5))CoI(2){Ph(2)PCH(2)C(O)Ph}] (1) and [(eta(5)-C(5)H(5))CoI(2){Ph(2)PNHC(O)Me}] (3), respectively, which upon reaction with excess NEt(3) yielded the phosphinoenolate complex [(eta(5)-C(5)H(5))CoI{Ph(2)PCH (center dot center dot center dot) under barC((center dot center dot center dot) under barO)Ph}] (2) and the phosphinoiminolate complex [(eta(5)-C(5)H(5))CoI{Ph(2)PN (center dot center dot center dot) under barC((center dot center dot center dot) under barO)Me}] (4), respectively. The complexes cis-[Ni{(i-Pr)(2)PN (center dot center dot center dot) under barC((center dot center dot center dot) under barO)Me}(2)] (6) and cis-[Ni{Ph(2)PN (center dot center dot center dot) under barC((center dot center dot center dot) under barO)Me}(2)] (7) were obtained similarly from NiCl(2) and HL(3) and HL(4), respectively, in the presence of a base. The phosphinoenolate complex [Ni{(i-Pr)(2)PCH (center dot center dot center dot) under barC((center dot center dot center dot) under barO) Ph}(2)] (5) exists in ethanol as a mixture of the cis and trans isomers, in contrast to cis-[Ni{(Ph(2)PCH (center dot center dot center dot) under barC((center dot center dot center dot) under barO)Ph}(2)], and the solid-state structure of the trans isomer of 5 was established by X-ray diffraction. The structures of the ligand HL3 and of the complexes 1, 3 in 3 center dot 3/2CH(2)Cl(2), 4, 6 and 7 have also been determined by X-ray diffraction and are compared with those of related complexes. Complexes 4, 6 and 7 contain a five-membered heteroatomic metallocyclic moiety, which is constituted by five different chemical elements. The structural consequences of the steric bulk of the P substituents and of the electronic characteristics of the P, O chelates are discussed.

{A new rigid bidentate ligand, bis(1-naphthylimino)acenaphthene, L1, and its Zn(II) and Pd(II) complexes {[}ZnCl(2)(L1)], 1, and {[}PdCl(2)(L1)], 2, were synthesized. L1 was prepared by the ``template method{''}, reacting 1-naphthyl amine and acenaphthenequinone in the presence of ZnCl(2), giving 1, which was further demetallated. Reaction of 1-naphthyl amine with acenaphthenequinone and PdCl(2) afforded dichloride bis(1-naphthyl)acenaphthenequinonediimine palladium, 2. L1, 1, and 2 were obtained as a mixture of syn and anti isomers. Compound 2 was also obtained by the reaction of PdCl(2) activated by refluxing it in acetonitrile followed by the addition of L1; by this route also a mixture of syn and anti isomers was obtained, but at a different rate. The solid-state structures of L1 and the anti isomer of compound 2 have been determined by single-crystal X-ray diffraction. All compounds have been characterized by elemental analyses; matrix-assisted laser desorption ionization-time-of-flight-mass spectrometry; IR; UV-vis; (1)H, (13)C, and (1)H-(1)H correlation spectroscopy; (1)H-(13)C heteronuclear single quantum coherence; (1)H-(13)C heteronuclear single quantum coherence-total correlation spectroscopy; and (1)H-(1)H nuclear Overhauser effect spectrometry NMR spectroscopies when applied. Density functional theory studies showed that both conformers for {[}PdCl(2)(BIAN)] are isoenergetic, and they can both be obtained experimentally. However, we can predict that the isomerization process is not available in a square-planar complex, but it is possible for the free ligand. The molecular geometry is very similar in both isomers, and only different orientations for naphthyl groups can be expected.}

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.

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.

Cobalt compounds of the general formula [COX2(alpha-diimine)], where X = Cl or I and the alpha-diimines are 1,4-diaryl-2,3-dimethyl-1,4-diaza-1,3-butadiene (Ar-DAB) and bis(aryl)acenaphthenequinonediimine (Ar-BIAN) were synthesized by the direct reaction of the anhydrous cobalt salts CoCl2 or CoI2 and the corresponding alpha-diinline ligand in dried CH2Cl2. The synthesized compounds are [Co(Ph-DAB)Cl-2] (1a), [Co(o,o',p-Me3C6H2-DAB)Cl-2] (1b), and [Co(o,o'iPr(2)C(6)H(3)-DAB)Cl-2] (1c) with the ligands Ar-DAB, and also [Co(o,o',p-Me3C6H2-BIAN)I-2] (2'b) with the ligand Ar-BIAN. The crystal structures of all the compounds were solved by single-crystal X-ray diffraction. In all cases the cobalt atom is in a distorted tetrahedron, which is built up of two halide atoms and two nitrogen atoms of the alpha-dimune ligand. X-band EPR measurements of polycrystalline samples performed on compounds 1b, 1c, and 2'b indicate a high-spin Col, ion (S = 3/2) in an axially distorted environment. Single-crystal EPR experiments on compounds 1b and 1c allowed us to evaluate the orientation of the g tensor in the molecular frame. (c) Wiley-VCH Verlag GmbH & Co.

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 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).

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).

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.