DSpace Angular :: Browsing by Author "Contreras, R"

Browsing by Author "Contreras, R"

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Ages and metallicities of Hickson compact group galaxies
(2004) Proctor, RN; Forbes, DA; Hau, GKT; Beasley, MA; De Silva, GM; Contreras, R; Terlevich, AI
Hickson compact groups (HCGs) constitute an interesting extreme in the range of environments in which galaxies are located, as the space density of galaxies in these small groups are otherwise only found in the centres of much larger clusters. The work presented here uses Lick indices to make a comparison of ages and chemical compositions of galaxies in HCGs with those in other environments (clusters, loose groups and the field). The metallicity and relative abundance of 'alpha-elements' show strong correlations with galaxy age and central velocity dispersion, with similar trends found in all environments. However, we show that the previously reported correlation between a-element abundance ratios and velocity dispersion disappears when a full account is taken of the abundance ratio pattern in the calibration stars. This correlation is thus found to be an artefact of incomplete calibration to the Lick system.
Bis(diphenylphosphino)amine and their dichalcogenide derivatives as ligands in rhodium(III), iridium(III), and ruthenium(II) complexes.: Crystal structures of [(η⁵-C₅Me₅)MCl{η²-(SePPh₂)₂N}] (M = Rh, Ir)
(2000) Valderrama, M; Contreras, R; Lamata, MP; Viguri, F; Carmona, D; Lahoz, FJ; Elipe, S; Oro, LA
Reaction of the dimers [{(eta(5)-C5Me5)MCl}(2)(mu-Cl)(2)] (M = Rh, Ir) or [{(eta(6)-arene)RuCl}(2)(mu-Cl)(2)] (arene = p-(MeC6H4Pr)-Pr-i, C6Me6) with NH(PPh2)(2) in the presence of AgA (A = BF4, PF6) leads to the mononuclear cationic complexes [(eta(5)-C5Me5)MCl{eta(2)- (PPh2)(2)NH}]A (M = Rh (1), Ir (2)) or [(eta(6)-arene)RuCl{eta(2)-(PPh2)(2)NH}]A (arene = p-(MeC6H4Pr)-Pr-i (3), C6Me6 (4)). Similar reactions using the chalcogenide derivatives NH(EPPh2)(2) (E = S, Se) yield the neutral complexes [(eta(5)-C5Me5)RhCl{eta(2)-(EPPh2)(2)N}] (E = S (5), Se (6)), [(eta(5)-C5Me5)IrCl{eta(2)-(EPPh2)(2)N}] (E = S (7), Se (8)), [(eta(6)-arene)RuCl{eta(2)-(SPPh2)(2)N}] (arene = C6H6 (9), p-(MeC6H4Pr)-Pr-i (10)) and [(eta(6)-arene)RuCl{eta(2)-(SePPh2)(2)N)}] (arene = C6Me6 (11), p-(MeC6H4Pr)-Pr-i (12)). Chloride abstraction from complexes 5-8 with AgPF6 in the presence of PPh3 gives the cationic complexes [(eta(5)-C5Me5)Rh{eta(2)-(EPPh2)(2)N}(PPh3)]PF6 (E = S (13), Se (14)) and [(eta(5)-C5Me5)Ir{eta(2)-(EPPh2)(2)N}(PPh3)]PF6 (E = S (15), Se (16)). Complexes 13-16 can also be synthesised from the starting dinuclear complexes, AgPF6, NH(EPPh2)(2) and PPh3. Using this alternative synthetic route the related ruthenium complexes [(eta(6)-C6Me6)Ru{eta(2)-(EPPh2)(2)N}(C5H5N)] BF4 (E = S (17), Se (18)) can be prepared. All described compounds have been characterised by microanalysis and NMR (H-1, P-31) and IR spectroscopy. The crystal structures of the neutral complexes [(eta(5)-C5Me5)MCl{eta(2)-(SePPh2)(2)N}] (M = Rh (6), Ir (8)) have been determined by X-ray diffraction methods. Both complexes exhibit analogous pseudo-octahedral molecular structures with a C5Me5 group occupying three coordination positions and a bidentate chelate Se,Se'-bonded ligand and a chloride atom completing the coordination sphere. (C) 2000 Elsevier Science S.A. All rights reserved.
Bis(diphenylphosphino)methylamine as chelate ligand in pentamethylcyclopentadienylrhodium(III) and iridium(III) complexes.: Crystal structure of [(η⁵-C₅Me₅)RhCl(η²-P,P′-(PPh₂)₂NMe}]BF₄
(2003) Valderrama, M; Contreras, R; Boys, D
Reactions of the dimers [{(eta(5) -C5Me5)MCl(mu-Cl)}(2)] (M = Rh, Ir) with the ligand NMe(PPh2)(2) in 1:2 molar ratio afford the mononuclear cationic complexes [(eta(5)-C5Me5)MCl{eta(2)-P,P'-(Ph2P)(2)NMe}]Cl (M = Rh 1, Ir 2). Similar iodide complexes, [(eta(5)- C5Me5)MCl{eta(2)-P,P'-(Ph2P)(2)NMe}]I (M = Rh 3, Ir 4), can be prepared by N-functionalization of co-ordinated dppa ligand in complexes [(eta(5) -C5Me5)MCl{eta(2)-P,P'-(Ph2P)(2)NH}]BF4. The tetrafluoroborate derivatives, [(eta(5)-C5Me5)MCl{eta(2)-P,P'- (Ph2P)(2)NMe}]BF4 (M = Rh 5, Ir 6) are prepared by reaction of complexes 1-4 with AgBF4 in acetone. All the compounds described are characterised by microanalysis, IR and NMR (H-1, P-31{H-1}) spectroscopy. The crystal structure of complex 5 is determined by X-ray diffraction methods. The complex exhibits a pseudo-octahedral molecular structure with a C5Me5 group occupying three co-ordination positions and a bidentate chelate P,P'-bonded ligand and a chloride atom completing the coordination sphere. (C) 2002 Elsevier Science B.V. All rights reserved.
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.
Comparison between experimental and theoretical scales of electrophilicity based on reactivity indexes
(2002) Pérez, P; Aizman, A; Contreras, R
A comparative study between a relative experimental scale of electrophilicity and a theoretical absolute scale based on electronic reactivity indexes is presented. The theoretical scale correctly predicts the experimental electrophilicity within the dihalogen and inter-halogen subseries (XY) including F-2, Cl-2, Br-2, BrCl, and CIF and the HX (X = F, Cl, Br) series. It is shown that the best correlation is obtained for the local electrophilic index that encompasses the global electrophilicity power weighted by a local factor described by the electrophilic Fukui function. This result is in agreement with the electrostatic model of Legon (Angew. Chem., Int. Ed. Engl. 1999, 38, 2686), as the electrophilic power of molecules is mainly determined by the local properties of the electrophilic ends of HX and XY species. We also evaluated the electrophilicity of Li-2, LiH, LiF, and LiCl species for which experimental data are not available. Whereas LiH is predicted to have an electrophilic potential comparable to that shown by the dihalogen and inter-halogen series but higher than that of the FIX species, LiF and LiCl are predicted to display an electrophilic pattern even higher that those of the XY and HX molecules. On the other hand, Li-2 displays an electrophilic pattern even lower than that of F-2.
Density functional theory study for the cycloaddition of 1,3-butadienes with dimethyl acetylenedicarboxylate. Polar stepwise vs concerted mechanisms
(2002) Domingo, LR; Arnó, M; Contreras, R; Pérez, P
The molecular mechanisms for the cycloaddition reactions of four low activated 1,3-butadiene systems (1,3-butadiene, (E)-1,3-pentadiene, (Z)-1,3-pentadiene, and 4-methyl-1,3-pentadiene) with dimethyl acetylenedicarboxylate (DMAD) have been studied using density functional theory method. For these cycloadditions, two competitive mechanisms have been characterized: the First one corresponds to a concerted C-C bond-formation where the asynchronicity depends on the methyl substitution. The second one corresponds to a stepwise process with a larger polar character where first a C-C bond is formed along the nucleophilic attack of 1,3-butadiene system to a conjugate position of the electron-poor substituted acetylene. Although the nonactivated 1,3-butadiene prefers the concerted process, substitution of hydrogen atoms by electron-releasing methyl groups favors the stepwise mechanism along with an increase of the charge-transfer process. A conformational analysis for DMAD reveals that both planar and perpendicular arrangements of the two-carboxylate groups have a decisive role on the dienophile/electrophile nature of this acetylene derivative. Thus, although the planar arrangement is preferred along the concerted process, the perpendicular favors the polar one along an increase of the electrophilicity of DMAD. The global and local electrophilicity power of these 1,3-butadienes and DMAD have been evaluated in order to rationalize these results. The study is completed with an analysis of the electrophilic/nucleophilic site activation, by probing the variations in local properties of DMAD perturbed by a model nucleophile with reference to a model transition structure. Inclusion of solvent effects, by means of a polarizable continuum model, does not modify these gas-phase results.
Diphenylphosphino(phenylthio)methane as a monodentate or bidentate chelate ligand in rhodium, iridium and ruthenium complexes, crystal structure of [(eta(5)-C(5)Me(5)) IrCl(eta(2)-Ph(2)PCH(2)SPh-P,S)]BF4 center dot Me(2)CO
(1997) Valderrama, M; Contreras, R; Boys, D
Reactions of complexes [{(eta(5)-C(5)Me(5))MCl(2)}(2)] (M = Rh, Ir) and [{(eta(6)-MeC(6)H(4)Pr(i))RuCl2}(2)] with the ligand Ph(2)PCH(2)SPh in acetone solution led to neutral complexes with the general formula [(ring)MCl(2)(eta(1)-Ph(2)PCH(2)SPh-P)] (1-3). These compounds react with thallium tetrafluoroborate in acetone solution to yield new cationic complexes in which the ligand is acting in its chelate P,S-donor fashion, [(ring)MCl(eta(2)Ph(2)PCH(2)SPh-P,S)]BF4 (4-6). When the removal of the chloride ligand in complexes 1-3 was carried out in the presence of a stoichiometric amount of Ph(2)PCH(2)SPh, cationic compounds containing two P-donor monodentate ligands of the type [(eta(5)-C(5)Me(5))MCl(eta(1)-Ph(2)PCH(2)SPh-P)(2)]BF4 (7 and 8) were obtained. The structure of the iridium derivative [(eta(5)-C(5)Me(5))IrCl(eta(2)-Ph(2)PCH(2)SPh-P,S)]BF4 . Me(2)CO has been determined by single-crystal X-ray diffraction methods. The complex cation contains a C(5)Me(5) group occupying three coordination positions of a distorted octahedral iridium centre, a bidentate chelate P,S-bonded ligand and a chloride atom completing the coordination sphere. (C) 1997 Elsevier Science Ltd.
Empirical energy-density relationships for the analysis of substituent effects in chemical reactivity
(2000) Pérez, P; Simón-Manso, Y; Aizman, A; Fuentealba, P; Contreras, R
Electronic substituent effects may be rationalized in terms of Hammett-like linear relationships between global energy-dependent quantities and local electronic descriptors of reactivity. These linear relationships are framed on a local hard and soft acids and bases (HSAB) principle in accord with previous results reported by Li and Evens [J. Am. Chem Sec. 1995, 117, 7756]. Chemical substitution is indirectly assessed as local responses at the active center of the substrate, with the Fukui function and local softness as the key quantities within the present approach. This model of chemical substitution has a potential advantage with respect to models based on group properties using the electronegativity equalization principle (EEP), since the transferability of group properties is not required. The formalism is illustrated for the gas-phase basicity of alkylamines, and the gas-phase acidity of alkyl alcohols and alkyl thioalcohols. Our results based on the local HSAB rule agree a ell with those obtained from group properties analysis based on the EEP, suggesting that bath empirical rules consistently complement each other.
Heterodinuclear PtRh and PtIr complexes with phosphinite groups as bridging ligands
(1998) Contreras, R; Valderrama, M; Moscoso, R
Compounds of the general formula [Pt(eta(2)-L) {P(O)Ph-2}{P(OH)Ph-2}], where eta(2)-L = {eta(2)-S2P(OEt)(2)}(-) (I) and {eta(2)-(SCNEt2)-C-2}(-) (2), react in THF solution with the dinuclear complex [{(cod)M(mu-OMe)}(2)] (M = Rh-I or Ir-I) to give new heterodinuclear compounds of the type [(eta(2)-L)Pt{mu-P(O)Ph-2}(2)M(cod)], where eta(2)-L = {eta(2)-S2P(OEt)(2)}(-); M = Rh-I (3), Ir-I (4) and eta(2)-L = {eta(2)-S2C-NEt2}(-); M = Rh-I (5) and Ir-I (6). Compounds (3) and (4) react with an excess of CO, leading to displacement of the coordinated pi-diolefin (cod) and the formation of the dicarbonyl derivatives [{eta(2)-S2P(OEt)(2)}Pt{mu-P(O)-Ph-2}(2)M(CO)(2)] [M = Rh-I (7), Ir-I (8)].
On the condensed Fukui function
(2000) Fuentealba, P; Pérez, P; Contreras, R
A critical comparison among recently proposed methods for evaluating the condensed Fukui function neglecting relaxation effects is presented. The sign of the condensed Fukui function is discussed and arguments for a positive definite condensed Fukui function are given. Our numerical calculations in two series of molecules show that: (i) the condensed Fukui function can give, in general, valuable information about the site selectivity in chemical reactions and systematization in a family of molecules. In particular, it has been shown that the selectivity towards protonation in anilines and derivatives molecules can be correctly assessed by the electrophilic Fukui function described in this paper. Within this approach non-negative values for the condensed Fukui function are obtained for the relevant protonation sites in these polyfunctional systems; and (ii) the solvent effects on the condensed Fukui function are negligible, confirming a recently presented theoretical prediction. (C) 2000 American Institute of Physics. [S0021-9606(00)30331-2].
Pentamethylcyclopentadienyliridium(III) complexes containing tertiary phosphorus chalcogenide ligands: Crystal structure of [(eta(5)C(5)Me(5))Ir{PO(OMe)(2)}{eta(2)(SPPh(2))(2)CH2-S,S'}]BF4 center dot 0.5Me(2)CO
(1996) Valderrama, M; Contreras, R
Neutral iridium(III) complexes of the unidentate P-donor ligands dppm, dppmS and dppmSe, and cationic complexes with these ligands acting in their bidentate form have been prepared and characterized. Similar cationic complexes with the symmetrical bidentate dichalcogenide ligands dppmS, and dppmSe, have been described. These compounds react with sodium hydride in tetrahydrofuran or with thallium pyrazolate in dichloromethane to yield the new cationic complexes [(eta(5)C(5)Me(5))Ir{eta(3)(EPPh(2))(2)CH-C,E,E'}](+) (E = S, Se) in which the anionic methanide dichalcogenide ligand is acting as a tripod ligand with a C,E,E'-donor set. However, the complexes [(eta(5)C(5)Me(5))IrCl(eta(2)dppmE(2))]BF4 react with P(OMe)(3) in the presence of TIBF4, to give the dicationic compounds [(eta(5)C(5)Me(5))Ir{P(OMe>(3)}(eta(2)dppmE(2))(BF4)(2). In these complexes, the P(OMe)(3) ligand is transformed into a coordinated PO(OMe)(2) group by reaction with sodium iodide in acetone. The structure of the complex [(eta(5)C(5)Me(5))Ir{PO(OMe)(2)}(eta(2)dppmS(2)-S,S')]BF4 . 0.5Me(2)CO have been determined by single crystal X-ray diffraction methods.
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.
Quantitative characterization of the global electrophilicity power of common diene/dienophile pairs in Diels-Alder reactions
(2002) Domingo, LR; Aurell, MJ; Pérez, P; Contreras, R
The global electrophilicity power, omega, of a series of dienes and dienophiles commonly used in Diels-Alder reactions may be conveniently classified within a unique relative scale. Useful information about the polarity of transition state structures expected for a given reaction may be obtained from the difference in the global electrophilicity power, Deltaomega. of the diene/dienophile interacting pair. Thus the polarity of the process can be related with non-polar (Deltaomega small, pericyclic processes) and polar (Deltaomega big, ionic processes) mechanisms. (C) 2002 Elsevier Science Ltd. All rights reserved.
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.
Spin-philicity and spin-donicity as auxiliary concepts to quantify spin-catalysis phenomena
(2002) Pérez, P; Andrés, J; Safont, VS; Tapia, O; Contreras, R
For molecular systems Susceptible to undergo a change of their spin state as a result of a chemical reaction with a given reactant, the spin-polarized density functional theory is used to define the concepts of "spin-philicity" (omega(S)(+)) and "spin-donicity" (omega(S)(-)) as global reactivity indexes. They are defined as the maximum energy change when a molecular system acquires or donates a spin number DeltaN(S) to increase (omega(S)(+)) or decrease (omega(S)(-)) its spin multiplicity. The spin transformation of chemically reactive species induced by the interaction of these molecules with external spin carriers-a phenomenon known as spin catalysis-is discussed on the basis of an absolute scale for omega(S)(+) and omega(S)(-). As an illustration of the method, a selection of paramagnetic and diamagnetic molecules, commonly used as spin catalyst. is classified within this scale and the hierarchy obtained is compared with the available experimental information.
Synthesis and characterization of heterodinuclear RuPt and IrPt complexes containing pyrazolate bridging ligands.: Crystal structure of [(η⁵-C₅Me₅)Ir(μ-pz)₃PtMe₃] (pz = pyrazolate)
(2000) Contreras, R; Valderrama, M; Orellana, EM; Boys, D; Carmona, D; Oro, LA; Lamata, MP; Ferrer, J
The reaction of the metallo-ligand [Ru(eta(6)-p-cymene)(pz)(2)(Hpz)] with the platinum complex [{PtIMe3}(4)] affords mixtures of the heterodinuclear complexes [(eta(6)-p-cymene)Ru(mu-pz)(3)PtMe3] (1) and [(eta(6)-p-cymene)Ru(mu-pz)(2)(mu-I)PtMe3] (2). The reaction of the iridium derivative [Ir(eta(5)-C5Me5)(pz)(2)(Hpz)] with [{PtIMe3}(4)] gives [(eta(5)-C5Me5)Ir(mu-pz)(2)(mu-I)PtMe3] (3). Both [Ru(eta(6)-p-cymene)(pz)(2)(Hpz)] and [Ir(eta(5)-C5Me5)(pz)(2)(Hpz)] react with [{PtIMe3}(4)] in the presence of NaOH yielding 1 and [(eta(5)-C5Me5)Ir(eta-pz)(3)PtMe3] (4), respectively. While [Ru(eta(6)-p-cymene)(pz)(2)(Hpz)] reacts with [PtBr2Me2Sx] to give mixtures of [(eta(6)-p-cymene)Ru(mu-pz)(3)PtBrMe2] (5) and [(eta(6)-p-cymene)Ru(mu-pz)(2)(mu-Br)PtBrMe2] (6), the reaction of [Ir(eta(5)-C5Me5)(pz)(2)(Hpz)] with [PtBr2Me2Sx] gives [(eta(5)-C5Me5)Ir(mu-pz)(2)(mu-Br)PtBrMe2] (7) as the sole product. All species were characterized in solution by H-1-NMR spectroscopy. The crystal structure of complex 4 has been determined by single-crystal X-ray diffraction. (C) 2000 Elsevier Science S.A. All rights reserved.
Synthesis and characterization of new dimethylplatinum(IV) complexes with O-(diphenylphosphino)thioanisole and its chalcogenide derivatives as ligands.: Crystal structure of trans-[Me₂PtBr₂{O-Ph₂P(S)C₆H₄SMe-S,S'}]
(2001) Contreras, R; Valderrama, M; Beroggi, C; Boys, D
The compound o-(diphenylphosphino)thioanisole can be oxidized by S or Se in benzene leading to the derivatives Ph2P(E)C6H4SMe [EPSMe: E = S (1), Se (2)]. These compounds act as bidentate chelate ligands in reactions with the platinum(IV) complex [Me2PtBr2](n) to form trans and cis isomers of the general formula [Me2PtBr2(L-2)] [L-2 = SPSMe (3, 4); SePSMe (5, 6)]. The reaction of the complex [Me2PtBr2](n) with the starting ligand Ph2PC6H4SMe (PSMe) led to a reductive elimination affording the neutral complex [PtBr2(PSMe)] (7). The structure of the complex [Me2PtBr2{o-Ph2P(S)C6H4SMe}] was established by X-ray crystallography. The platinum atom has a distorted octahedral coordination and it is bonded to two methyl carbons, two bromide atoms and two sulfur atoms of the (o-diphenylphosphinesulfide)thioanisole bidentate ligand. (C) 2001 Elsevier Science Ltd. Ail rights reserved.
Synthesis and characterization of new homo-heterobinuclear platinum(II) complexes with dimethylphosphonate as bridging ligands. Crystal structure of [(eta(2)dppm)Pt{mu-P(O)(OMe)(2)}(2)(mu-I)PtMe(3)]
(1997) Contreras, R; Valderrama, M; Nettle, A; Boys, D
The preparation of the new neutral complex [(eta(2)-dppm)Pt{P(O)(OMe)(2)}(2)] (1) (dppm = 1,1-bis(diphenylphosphino) methane) and its behaviour as a chelate (O,O)-donor ligand is described. This ligand reacts with [Me(3)PtI](4) to give the homobimetallic complex [(eta(2)dppm)Pt{mu-P(O)(OMe)(2)}(2)(mu-I)PtMe(3)] (2), which in turn reacts with AgPF6 in the presence of PPh(3) to yield the new cationic complex [(eta(2)dppm)Pt{mu-P(O)(OMe)(2)}(2){PtMe(3)(PPh(3))}]PF6 (3). In contrast, the treatment of binuclear complexes [{Pd(mu-Cl)(2-MeC(3)H(4))}(2)] and [{Rh(mu-Cl)(cod)}(2)] with silver perchlorate in the presence of the bidentate ligand 1 yields the heterobinuclear compounds [(eta(2)dppm)Pt{mu-P(O)(OMe)(2)}Pd-2(eta(3)MeC(3)H(4))]ClO4 (4) and [(eta(2)dppm)Pt{mu-P(O)(OMe)(2)}Rh-2(cod)]ClO4 (5). Complex 5 reacts with an atmosphere of CO at room temperature yielding the cis-dicarbonyl complex [(eta(2)dppm)Pt{mu-P(O)(OMe)(2)}Rh-2(CO)(2)]ClO4 (6). The structure of complex [(eta(2)dppm)Pt{mu-P(O)(OMe)(2)}(2)(mu-I)PtMe(3)] has been determined by single crystal X-ray diffraction methods.
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.
Synthesis of rhodium(III) complexes with the chiral phosphine (S)-Ph₂PCH₂CHMeCH₂OH.: Crystal structure of (S_RhS_C)-[(η⁵-C₅Me₅)RhCl(η²-PPh₂CH₂CHMeCH₂OH-P,O)]BF₄
(2001) Valderrama, M; Contreras, R; Araos, G; Boys, D
Reaction of dinuclear complex [{(eta (5)-C5Me5)RhCl}(2)(mu -Cl)(2)] with the chiral phosphine (S)-Ph2PCH2CHMeCH2OH leads to the complex [{eta (3)-C5Me5)RhCl2(eta (1)-PPh2CH2CHMeCH2OH-P)] (1). Complex 1 reacts with NaH and T1BF(4) affording the chiral-at-metal rhodium compounds [(eta (5)-C5Me5)RhCl(eta (2)-PPh2CH2CHMeCH2O-P,O)] (2) and [(eta (5)-C5Me5)RhCl(eta (2)-PPh2CH2CHMeCH2OH-P,O)]BF4(3), respectively. Complex 2 has been alternatively prepared by reaction of [{(eta (5)-C5Me5)RhCl}(2)(mu -Cl)(2)] with the sodium salt Ph2PCH2CHMeCH2ONa. Complex 2 reacts with HBF, to give 3. The reaction of 3 with an excess of NaI affords the neutral complex [(eta (5)-C5Me5)RhI2(eta (1)-PPh2CH2CHMeCH2OH-P)] (4). All the complexes have been characterised by elemental analyses and multinuclear NMR spectroscopy. The crystal structure of complex 3 has been determined by X-ray diffraction. (C) 2001 Elsevier Science B.V. All rights reserved.

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