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Montagner D.,University of Padua | Sanz Miguel P.J.,Institute Sintesis Quimica y Catalisis Homogenea ISQCH
Dalton Transactions | Year: 2011

The neutral complex [PtCl(PyDT)]5 (PyDT = (CH2) 4NCS2 -) represents the first example of a Pt5 metallacycle. This unique architecture based on chiral S-bridged PtII monomers was prepared by thermal degradation of the reaction product of PtCl2 and a pyrrolidinedithioester. © 2011 The Royal Society of Chemistry. Source

Fornies J.,University of Zaragoza | Fuertes S.,University of Zaragoza | Larraz C.,University of Zaragoza | Martin A.,University of Zaragoza | And 3 more authors.
Organometallics | Year: 2012

Double complex salts (DCSs) of stoichiometry [Pt(bzq)(CNR) 2][Pt(bzq)(CN) 2] (bzq = 7,8-benzoquinolinate; R = tert-butyl (1), 2,6-dimethylphenyl (2), 2-naphtyl (3)) have been prepared by a metathesis reaction between [Pt(bzq)(CNR) 2]ClO 4 and [K(H 2O)][Pt(bzq)(CN) 2] in a 1:1 molar ratio under controlled temperature conditions (range: -10 to 0 °C). Compounds 1-3 have been isolated as air-stable and strongly colored solids [purple (1), orange (2), red-purple (3)]. The X-ray structure of 2 shows that it consists of ionic pairs in which the cationic and anionic square-planar Pt(II) complexes are almost parallel to each other and are connected by Pt-Pt (3.1557(4) Å) and π⋯π (3.41-3.79 Å) interactions. Energy decomposition analysis calculations on DCSs 1-3 showed relatively strong ionic-pair interactions (estimated interaction energies of -99.1, -110.0, and -108.6 kcal/mol), which are dominated by electrostatic interactions with small contributions from dispersion (π⋯π) and covalent (Pt⋯Pt) bonding interactions involving the 5d and 6p atomic orbitals of the Pt centers. Compounds 1-3 undergo a thermal (165 °C, 24 h) irreversible ligand rearrangement process in the solid state and also in solution at temperatures above 0 °C to give the neutral complexes [Pt(bzq)(CN)(CNR)] as a mixture of two possible isomers (SP-4-2 and SP-4-3). The mechanism of this process has been thoroughly explored by combined NMR and DFT studies. DFT calculations on 1-3 show that the existing Pt⋯Pt interactions block the associative attack of the Pt(II) centers by the coordinated cyanide and/or isocyanide ligands. Moreover, they support a significant transfer of electron density from the anionic to the cationic component (0.20-0.32 |e|), which renders the isocyanide ligand dissociation more feasible than that in the "free-standing" cationic [Pt(bzq)(CNR) 2] + components as well as the dissociation of the CN - in trans position to the C bzq in the anionic [Pt(bzq)(CN) 2] - component. Therefore, the first step in the ligand rearrangement pathway is the dissociation of the isocyanide in trans position to the C bzq, yielding the [(RNC)(bzq)(μ 2- η 1,η 1-CN)Pt⋯Pt(bzq)(CN)] intermediates. The rate-limiting step corresponds to the transformation of these intermediates to the neutral [Pt(bzq)(CN)(CNR)] complexes following a synchronous mechanism involving rupture of the Pt-Pt and formation of the Pt-CN bonds through transition states formulated as [(RNC)(bzq)Pt(μ 2- η 1,η 1-CN)Pt(bzq)(CN)]. © 2012 American Chemical Society. Source

Arias A.,University of Zaragoza | Fornies J.,University of Zaragoza | Fortuno C.,Institute Sintesis Quimica y Catalisis Homogenea ISQCH | Martin A.,University of Zaragoza
Inorganica Chimica Acta | Year: 2013

The di- and trinuclear derivatives [(RF)2Pt(μ- PPh2)2Pt(CH3CN)2], 1, [(R F)2Pt(μ-PPh2)2Pt(μ-PPh 2)2Pt(CH3CN)2], 2, (RF = C6F5) behave as synthons of di- and trinuclear fragments. Addition of azide and oxalate ions to 1 and 2, even in an excess, provides a way to isolate the tetranuclear and hexanuclear platinum complexes [NBu 4]2[{(RF)2Pt{(μ-PPh 2)2Pt}n(μ-1,1-N3)}2] (n = 1, 3; 2, 5), [NBu4]2[{(RF) 2Pt(μ-PPh2)2Pt}2(μ-C 2O4-κ2O,O′: κ 2O″,Oâ€́)}], 4, and [NBu4] 2[{(RF)2Pt(μ-PPh2) 2Pt(μ-PPh2)2Pt}2(μ-C 2O4-κ2O,O′: κ 2O″,Oâ€́)}], 6. The structures of 3-6, determined by single crystal X-ray diffraction, show a linear arrangement of the platinum centres maintained through "Pt(μ-PPh2) 2Pt" and "Pt(μ-1,1-N3)2Pt" or "Pt(μ-C2O4-κ2O,O′: κ2O″,Oâ€́)Pt" bridging fragments. Finally, addition of KCN to 2 affords the trinuclear [NBu4] 2[(RF)2Pt(μ-PPh2) 2Pt(μ-PPh2)2Pt(CN)2], 7, in which two cyanido groups are bonded to the platinum centre in a terminal way. © 2013 Elsevier B.V. All rights reserved. Source

Sadaba D.,Institute Sintesis Quimica y Catalisis Homogenea ISQCH | Delso I.,Institute Sintesis Quimica y Catalisis Homogenea ISQCH | Delso I.,University of Zaragoza | Tejero T.,Institute Sintesis Quimica y Catalisis Homogenea ISQCH | Merino P.,Institute Sintesis Quimica y Catalisis Homogenea ISQCH
Tetrahedron Letters | Year: 2011

Optically active five-membered cyclic nitrones are readily obtained in a one-pot procedure via the organocatalytic Michael addition of aldehydes to nitroolefins and in situ reductive cyclization. Application of the methodology to the synthesis of tricyclic compounds through intramolecular 1,3-dipolar cycloaddition reactions (DFT calculations have also been performed) is also demonstrated. All the reactions were carried out in water as a solvent and excellent ee values (ee >99%) were obtained. © 2011 Elsevier Ltd. All rights reserved. Source

Lazaro G.,Institute Sintesis Quimica y Catalisis Homogenea ISQCH | Fernandez-Alvarez F.J.,Institute Sintesis Quimica y Catalisis Homogenea ISQCH | Munarriz J.,Institute Biocomputacion Y Fisica Of Sistemas Complejos Bifi | Polo V.,Institute Biocomputacion Y Fisica Of Sistemas Complejos Bifi | And 4 more authors.
Catalysis Science and Technology | Year: 2015

The rhodium(i)-NHC (NHC = N-heterocyclic carbene) complex [Rh(Cl)(COD)(2-methoxyphenyl-NHC-(CH2)3Si(OiPr)3)] (2a) catalyzes the solvent-free homogeneous hydrosilylation of acetophenone with HSiMe(OSiMe3)2. Kinetic studies show that 2a behaves differently to the related homogeneous catalysts [Rh(Cl)(COD)(R-NHC-(CH2)3Si(OiPr)3)] (R = 2,6-diisopropylphenyl (2b); R = 2-methoxyethyl (2c)). This behavior could be attributable to the participation of different catalytic active species. Indeed, 1H NMR studies of the reaction of 2a with HSiMe(OSiMe3)2 evidenced the formation of a new hydrido-bridged binuclear complex, namely {[Rh(SiMe(OSiMe3)2)(κ-C,C′-R-NHC-(CH2)3Si(OiPr)3)]2(μ-H)2} (R = 2-methoxyphenyl, 3), featuring orthometallated NHC and terminal silyl ligands, which has been proposed as the resting species in the hydrosilylation of acetophenone with HSiMe(OSiMe3)2 catalyzed by 2a. Moreover, the heterogeneous catalyst 2a-MCM-41 evidenced a behavior similar to the homogeneous catalyst 2a in the solvent-free hydrosilylation of acetophenone with HSiMe(OSiMe3)2. © 2015 The Royal Society of Chemistry. Source

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