Browsing by Author "Lopez, JA"

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    Simultaneous multiwavelength observations of dwarf novae .1. SU Ursae Majoris: Minihumps at a minioutburst?
    (1996) Echevarria, J; Tovmassian, G; Shara, M; Tapia, M; Bohigas, J; Jones, DHP; Gilmozzi, R; Costero, R; Lopez, JA; Roth, M; Alvarez, M; Rodriguez, LF; DeLara, E; Stover, RJ; MartinezRoger, C; Garzon, F; Asatrian, N; Vogt, N; Szkody, P; Zsoldos, E; Mattei, J; Bateson, FM
    SU Ursae Majoris-the prototype of a subgroup of dwarf novae that display superhumps in superoutbursts has been observed during an international campaign dedicated to the observation of the first day of outburst of dwarf novae during 1986 February. After the start of a brightening was reported, the star was monitored by IUE, ground-based photometry and spectrophotometry, IR-photometry, and radio observations by VLA. However, it did not undergo a normal outburst or a superoutburst.
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    Tris(diphenylthiophosphinoyl)methanide as tripod ligand in rhodium(III), iridium(III) and ruthenium(II) complexes.: Crystal structures of [(η5-C5Me5)Ir{η3-(SPPh2)3C-S,S′,S"}]BF4 and [(η6-MeC6H4Pri)Ru{η3-(SPPh2)3C-S,S′,S"}]BPh4
    (1997) Valderrama, M; Contreras, R; Arancibia, V; Munoz, P; Boys, D; Lamata, MP; Viguri, F; Carmona, D; Lahoz, FJ; Lopez, JA; Oro, LA
    Reaction of the complex [{(eta(5)-C5Me5)RhCl2}(2)], in CH2Cl2 solution, with AgBF4 (1:2 molar ratio) and (SPPh2)(3)CH leads to the cationic compound [(eta(5)-C5Me5)RhCl{eta(2)-(SPPh2)(2)CH(SPPh2)-S,S'}]BF4 (1) which is deprotonated by thallium(I) pyrazolate affording [(eta(5)-C5Me5)Rh{eta(3)-(SPPh2)(3)C-S,S',S "}]BF4 (2a). The iridium dimer [{(eta(5)-C5Me5)IrCl2}(2)] reacts with silver salts and (SPPh2)(3)CH, in CH2Cl2 or Me2CO, under analogous conditions, affording mixtures of [(eta(5)-C5Me5)IrCl{eta(2)-(SPPh2)(2)CH(SPPh2)-S,S'}](+) and [(eta(5)-C5Me5)Ir{eta(3)-(SPPh2)(3)C-S,S',S "}]A [A = BF4- (3a), PF6- (3b)]. Addition of Et3N to the mixture gives pure complexes 3. The ruthenium complexes [{(eta(6)-arene)RuCl2}(2)] (arene = C6Me6, p-MeC6H4Pri) react with (SPPh2)(3)CH, in the presence of AgA (A = PF6- or BF4-) or Na BPh4, in CH2Cl2 or Me2CO, yielding only the deprotonated complexes [(eta(6)-arene)Ru{eta(3)-(SPPh2)(3)C-S,S',S "}]A [arene = C6Me6, A = BF4; arene = p-MeC6H4Pri, A = BPh4 (4a), PF6 (4b)]. The crystal structures of 3a and 4a were established by X-ray crystallography. Compound 3a crystallizes in the orthorhombic space group Pna2(1), with lattice parameters a = 41.477(6), b = 10.6778(11), c = 20.162(3) Angstrom and Z = 8. Complex 4a crystallizes in a monoclinic lattice, space group P2(1)/n, with a = 20.810(4), b = 12.555(3), c = 23.008(4) Angstrom, beta = 95.82(2)degrees and Z = 4. Both cationic complexes exhibit analogous pseudo-octahedral molecular structures with the anionic (SPPh2)(3)C- ligand bonded via the three sulphur atoms in a tripodal, tridentate fashion. Each metal centre completes its coordination environment with a eta(5)-C5Me5 (3a) or a eta(6)-MeC6H4Pri group (4a). A quite interesting result concerns the non-planarity of the methanide carbon which display P-C-P angles in the range 112.6-114.4(5)degrees in 3a and 111.9-113.6(4)degrees in 4a. The redox chemistry of the complexes was investigated by cyclic voltammetry. The Rh(III) complexes are quasi-reversibly reduced to Rh(I) and the Ir(III) complex is irreversibly reduced to Ir(I) in acetonitrile solutions. The Ru(II) complex undergoes a quasi-reversible reduction to Ru(I) and a reversible oxidation to Ru(III). (C) 1997 Elsevier Science S.A.