Browsing by Author "Valderrama, M"

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    C-Pt(IV) activation in new trimethylplatinum(IV) complexes: nucleophilic attack at metal-carbon bond
    (ELSEVIER SCIENCE SA, 2003) Romero, P; Valderrama, M; Contreras, R; Boys, D
    Reaction of the tetranuclear complex [Me3PtI](4) with the ligand o-Ph2P(E)C6H4SMe (E = S, Se) in a 1:4 molar ratio yields the mononuclear neutral complexes [Me3PtI(eta(2)-MeSC6H4P(E)Ph-2-S,S)] (E = S(1), Se(2)). Iodide abstraction from these compounds with AgPF6 in the presence of a ligand L (PPh3, py) leads to cationic complexes of the type [Me3Pt(eta(2)-MeSC6H4P(E)Ph-2-E,S)L]PF6 [E = S, L = PPh3 (3), Py (4); E = Se, L = Py (5)]. However, using complex 2 and the ligand PPh3 under identical conditions induces a reductive elimination reaction affording the Pt(II) complex [MePt(eta(2)-MeSC6H4PPh2-P,S)(PPh3)]PF6 (6). Reactions of complexes 3 and 4 with NaI reveal a nucleophilic attack of the iodide to one of the methyl groups bonded to the platinum center generating a series of subsequent side reactions. Complex [Me3Pt{eta(2)-MeSC6H4P(S)Ph-2-S,S}(py)]PF6.CH2Cl2 (4) was additionally characterised by X-ray diffraction. The platinum atom exhibits a distorted octahedral coordination, bonded to three methyl carbon atoms in a facial arrangement; a bidentate chelate S,S'-bonded ligand and a nitrogen atom of the pyridine ligand complete the metal coordination sphere. (C) 2003 Elsevier Science B.V. All rights reserved.
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    Group VIII transition metal complexes with the chiral diphosphazane ligand (S)-alpha-(Ph2P)(2)N(CHMePh): Synthesis and structural characterization
    (ELSEVIER SCIENCE SA, 2006) Simon Manso, E; Valderrama, M
    The chiral ligand S-(Ph2P)(2)N(CHMePh) reacts with Ni(CO)(4) in benzene solution to yield the mononuclear complex [Ni(CO)(2)]{kappa(2)-(PPh2)2N(CHMePh))] (1). The reactions of the chiral ligand with the solvated complexes [(eta(5)-C5Me5)MCl(solvent)(2)]BF4 (M = Rh, Ir) or with the binuclear complex [{(eta(6)-C6Me6)RuCl}(2)(mu-Cl)] in the presence of a chloride scavenger, give cationic complexes of the type [(eta(5)-ring)MCl(kappa(2)-(PPh2)(2)N(CHMePh)]BF4 [eta(5)-ring = -C5Me5; M = Rh (2), Ir (3). eta(6)-C6Me6; M = Ru (4)]. The P-31 NMR spectra of compounds 2-4 show two signals corresponding of two phosphorus nuclei with different chemical environments. The related complex [(eta(5)-C5H5)Fe(CO)(kappa(2)-(PPh2)(2)N(CHMePh))]BF4 (5) was prepared by reaction of the ligand with the complex [(eta(5)-C5H5)Fe(CO)(2)I) in toluene following by a metathesis with AgBF4. This compound exhibits only one signal in the 31P NMR spectra at room temperature, which splits into two signals at low temperature (213 K). The crystal structures of complexes 2, 3 and 5 have been determined by X-ray diffraction studies. All complexes show the presence of an intramolecular n-stacking interaction. The separation between least-squares planes defined by the two intramolecularly stacked phenyl rings are in the range 3.318-3.649 (c) 2005 Elsevier B.V. All rights reserved.
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    Platinum(II) complexes with dithiolates and phosphinites as ligands: Crystal structure of [Pt{S2CO}{P(OMe)Ph(2)}(2)]
    (PERGAMON-ELSEVIER SCIENCE LTD, 1996) Contreras, R; Valderrama, M; Riveros, O; Moscoso, R; Boys, D
    Reaction of the complex [PtCl{P(O)Ph(2)} {P(OH)Ph(2)}(2)] with silver or thallium derivatives of dithiolate ligands led to neutral complexes of general formula [Pt{S-S} {P(O)Ph(2)} {P(OH)Ph(2)}], where {S-S}(-) ={S(2)CNEt(2)}(-) (1), {S2P(OEt)2}(-) (2) and {S(2)COEt}(-) (3). Complexes 2 and 3 reacted with an excess of NaI in acetone solution by dealkylation of the coordinated dithiolate ligand and formation of the compounds [Pt{S2P(O) (OEt)} {P(O)Ph(2)} {P(OH)Ph(2)}] Na (4) and [Pt{S2CO}{P(O)Ph(2)}{P(OH)Ph(2)}] Na (5), respectively. The corresponding tetraphenylphosphonium derivatives (6, 7) were prepared by a metathetical reaction of these complexes with Ph(4)PBr in acetone solution. Related dithiolate complexes were obtained by reaction of the complex [Pt{S-S}(2)] with P(OMe)Ph(2) in molar ratio 1:2. Thus, the reaction of [Pt{S(2)COEt}(2)] in dichloromethane solution at room temperature gave [Pt{S(2)COEt} {P(OMe)Ph(2)}(2)] Cl (8). This complex reacted with NaI in acetone to form the neutral compound [Pt{S2CO} {P(OMe)Ph(2)}(2)] (9). When the reaction was carried out in dichloromethane at reflux temperature using [Pt{S2P(OEt)(2)}(2)] as starting material, the neutral compound [Pt{S2P(O)(OEt)} {P(OMe)Ph(2)}(2)] (10) was obtained. The crystal structure of the complex 9 has been determined by X-ray diffraction. The neutral complex shows a nearly square-planar coordination of the metal and a planar dithiocarbonate ligand.
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    Rhodium(III) and ruthenium(II) complexes with the chiral phosphine-alcohol PH2PCH2CHMeCH2OH. Synthesis and characterisation
    (SOC CHILENA QUIMICA, 2002) Sanhueza, J; Contreras, R; Valderrama, M
    Reaction of the dinuclear complex [{(eta(5)-C5Me5)RhCl}(2)(mu-Cl)(2)] with the chiral phosphine (R)-Ph2PCH2CHMeCH2OH leads to the complex [{(eta(5)-C5Me5)RhCl2(eta(1)-Ph2PCH2CHMeCH2OH-P)}](1). This reaction, in the presence of AgBF4, yields the cationic compound [{(eta(5)-C5Me5)RhCl(eta(2)-Ph2PCH2CHMeCH2OH-P,O)}]BF4 (2). Variable-temperature H-1 NMR and circular dichroism experiments support the stereoselective eta(2)-chelate coordination of the ligand and the proposed configuration for the metal centre. In a similar way, the reaction of the dimer [{(eta(6)-C6Me6)RuCl}(2)(mu-Cl)(2)] with the ligands (R)- and (S)-Ph2PCH2CHMeCH2OH afford the neutral complexes [(eta(6)-C6Me6)RuCl2{eta(1)-PPh2CH2CHMeCH2OH-P}] [R-ligand (3), S-ligand (4)], which in turn react with AgBF4 to give the cationic compounds [(eta(6)-C6Me6)RuCl{eta(2)-PPh2CH2CHMeCH2OH-P,O}]BF4 [R-ligand (5), S-ligand (6)]. All complexes have been characterised by elemental analysis, IR and multinuclear NMR spectroscopies.
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    Syntheses and characterization of binuclear Rh-2, Ir-2 and RhIr complexes containing dimethyl phosphonate and pyrazolate bridging ligands
    (ROYAL SOC CHEMISTRY, 1996) Valderrama, M; Cuevas, J; Boys, D; Carmona, D; Lamata, MP; Viguri, F; Atencio, R; Lahoz, FJ; Oro, LA
    The reaction of [Ir(eta(5)-C(5)Me(5))I{PO(OMe)(2)}{P(OH)OMe)(2)}] with pyrazole (Hpz) in the presence of AgPF6 gave [Ir(eta(5)-C(5)Me(5)){PO(OMe)(2)}{P(OH)(OMe)(2)}(Hpz)]PF6 1. Deprotonation of 1 with sodium carbonate afforded the neutral compound [Ir(eta(5)-C(5)Me(5)){PO(OMe)(2)}(2)(Hpz)] 2 which, in turn, can be deprotonated to [(eta(5)-C(5)Me(5))Ir{PO(OMe)(2)}(2)(pz)M'] (M' = Tl 3 or Na 4) by Tl(acac) (acac = acetylacetonate) or NaH, respectively. The complex [Ir(eta(5)-C(5)Me(5))I-2{P(OH)(OMe)(2)}] 5, prepared by cleaving the iodide bridges in [{Ir(eta(5)-C(5)Me(5))I}(2)(mu-I)(2)] with HPO(OMe)(2), reacted with Hpz in the presence of AgPF6 to give [Ir(eta(5)-C(5)Me(5)){PO(OMe)(2)}(Hpz)(2)]PF6 6. Complexes of formulae [(eta(5)-C(5)Me(5))Ir{PO(OMe)(2)(pz)M '' L(2)][M '' L(2) = Rh(CO)(2) 7, Rh(cod) 8 or Ir(cod) 9] were prepared from 2 [Rh(acac)(CO)(2)] or from 3 and the appropriate [{M ''(cod)}(2)(mu-Cl)(2) dimer (cod = cycloocta-1,5-diene). Complex 6 reacted with [{Rh(cod)}(2)(mu-Cl)(2)] in basic medium to give [(eta(5)-C(5)Me(5))Ir{PO(OMe)(2)}(pz)(2)Rh(cod)] 10. The rhodium-thallium compound [(eta(5)-C(5)Me(5))Rh{PO(OMe)(2)}(2)(pz)Tl] or the in situ prepared sodium derivative [(eta(5)-C(5)Me(5))Rh{PO(OMe)(2)}(pz)(2)Na] reacted with the dimers [{M ''(diolefin)}(2)(mu-Cl)(2)] affording [(eta(5)-C(5)Me(5))Rh{PO(OMe)(2)}(2)(pz)M ''(diolefin) = [M ''(diolefin) = Ir(cod) 11 or Rh(nbd) 12] or [(eta(5)-C(5)Me(5)){PO(OMe)(2)}Rh(pz)(2)}Rh(pz)(2)M ''(diolefin)][M ''(diolefin) = Rh(cod) 13, Ir(cod) 14 or Rh(nbd) 15], respectively (nbd = bicyclo[2.2.1]hepta-2,5-diene). Related heterovalent complexes of general formula [I(eta(5)-C(5)Me(5))M{PO(OMe(2)}(2)M ''(diolefin)][M = Ir, M'(diolefin) = Rh(cod) 16 or Ir(cod) 17; M = Rh, M ''(diolefin) = Rh(cod) 18, Ir(cod) 19, or Rh(nbd) 20] have been prepared starting from the mononuclear complexes [M(eta(5)-C(5)Me(5))I{PO(OMe)(2)}{P(OH)(OMe)(2)}] (M = Ir or Rh). All the complexes have been characterized by spectroscopic of 8 by toluene-p-sulfonic acid is reported. The structures of 8 and 16 have been determined by X-ray diffraction methods. Both complexes consist of doubly bridged binuclear (C(5)Me(5))Ir-Rh(cod) species, where the Ir atoms exhibit pseudo-octahedral co-ordination and the rhodium square planar. The bridging system in 16 is formed by two identical P,O-bonded phosphonate groups, while in 8 a pyrazolate and a phosphonate ligand are bridging the metals. The intermetallic separations are 4.0445(9) (8) and 4.0928(9) Angstrom (16).
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    Synthesis and reactivity of new trimethylplatinum(IV) complexes containing chiral Schiff bases as ligands: Crystal structure of (OC-6-44-C)-[PtIMe3{kappa(2)-(R)-Ph2P(C6H4)CH=NC*H(Ph)Me-P,N}]
    (ELSEVIER SCIENCE SA, 2006) Ramirez, P; Contreras, R; Valderrama, M; Boys, D
    Reaction of the tetranuclear complex [PtIMe3](4) with the ligand (S)- and (R)-Ph2P(C6H4)CH=NC*H(Ph)Me in a 1:4 molar ratio yields the mononuclear neutral complexes in diastereoisomeric mixtures [PtIMe3{K-2-Ph2P(C6H4)CH=NC*H(Ph)Me-P,N}]. Iodide abstraction from mixture with AgBF4 in the presence of pyridine (Py) induces a reductive elimination reaction with loss of ethane, leading to the cationic complex [PtMe(Py) {kappa(2) -Ph2P(C6H4)CH=NC*H(Ph)Me-P,N}[BF4] [C* = (S)-, 3; (R)-, 4]. When this reaction was carried out in the presence of PPh3 a consecutive orthometallation reaction with loss of methane is produced, forming the cationic complex [Pt(PPh3){kappa(3)-Ph2P(C6H4)CH=NC*H(C6H4)Me-C,P,N][BF4], [(S)-, 5; (R)-, 6]. All species were characterised in solution by H-1 and P-31{H-1} NMR spectroscopy, elemental analysis and mass spectrometry.