Browsing by Author "Boys, D"

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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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    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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    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.
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    Synthesis, crystal structure, molecular orbital calculations and electronic properties of 2,3-di(2-pyridyl)naphtho[2,3-f]quinoxaline-7,12-quinone (Aqdpp)
    (ROYAL SOC CHEMISTRY, 1998) Lopez, R; Boys, D; Loeb, B; Zuloaga, F
    The synthesis, characterization and crystal structure of 2,3-di(2-pyridyl)naphtho[2,3-f]quinoxaline-7,12-quinone (Aqdpp) are reported. Molecular orbital calculations have been carried out in order to characterize its reactivity and coordination properties. surface maps for the electronegativity, hardness and Fukui functions have been generated to identify local reactivity sites and the crystal structure has been compared with the optimized geometry with good correlation among them. The acceptor properties of the Aqdpp ligand are shown by the orbital map for the LUMO level contributed mainly by the quinonic region of the ligand.