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Synthesis, Characterization, Solution Behavior and Theoretical Studies of Pd(II) Allyl Complexes with 2-Phenyl-3H-indoles as Ligands

1
Secció de Química Inorgànica, Departament de Química Inorgànica i Orgànica, Universitat de Barcelona, Martí i Franquès 1–11, E-08028 Barcelona, Spain
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Institut de Química Teòrica i Computacional, Universitat de Barcelona. Martí i Franquès 1–11, E-08028 Barcelona, Spain
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Unitat de Difracció de Raigs-X, Centre Científics i Tecnològics (CCiT) Universitat de Barcelona, Solé i Sabaris 1–3, E-08028 Barcelona, Spain
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Department de Cristal·lografia, Mineralogia i Dipòsits Minerals, Facultat de Geologia, Universitat de Barcelona, Martí i Franqués s/n, E-08028 Barcelona, Spain
*
Author to whom correspondence should be addressed.
Catalysts 2019, 9(10), 811; https://doi.org/10.3390/catal9100811
Received: 9 September 2019 / Revised: 24 September 2019 / Accepted: 24 September 2019 / Published: 27 September 2019
(This article belongs to the Special Issue Ligand Design in Metal Chemistry: Reactivity and Catalysis)
The study of the reactivity of three 2-phenyl-3H-indole ligands of general formulae C8H3N-2-(C6H4-4-R1)-3-NOMe-5-R2 (1) [with R1 = H, R2 = OMe (a); R1 = R2 = H (b) or R1 = Cl, R2 = H (c)] with [Pd(η3-1-R3C3H4)(μ-Cl)]2 (R3 = H or Ph) has allowed us to isolate two sets of new Pd(II)-allyl complexes of general formulae [Pd(η3-1-R3C3H4)(1)Cl] {R3 = H (2) or Ph (3)}. Compounds 2a–2c and 3a–3c were characterized by elemental analyses, mass spectrometry and IR spectroscopy. The crystal structures of 2a, 3a and 3b were also determined by X-ray diffraction. 1H-NMR studies reveal the coexistence of two (for 2a–2c) or three (for 3a–3c) isomeric forms in CD2Cl2 solutions at 182 K. Additional studies on the catalytic activity of mixtures containing [Pd(η3-C3H5)(μ-Cl)]2 and the parent ligand (1a–1c) in the allylic alkylation of (E)-3-phenyl-2-propenyl (cinnamyl) acetate with sodium diethyl 2-methylmalonate as well as the stoichiometric reaction between compounds 3a and 3c with the nucleophile reveal that in both cases the formation of the linear trans- derivative is strongly preferred over the branched product. Computational studies at a DFT level on compound 3a allowed us to compare the relative stability of their isomeric forms present in solution and to explain the regioselectivity of the catalytic and stoichiometric processes. View Full-Text
Keywords: Pd-allyl complexes; 2-phenyl-3H-indoles; homogeneous catalysis; computational studies; solution behavior Pd-allyl complexes; 2-phenyl-3H-indoles; homogeneous catalysis; computational studies; solution behavior
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MDPI and ACS Style

Tomé, M.; Grabulosa, A.; Rocamora, M.; Aullón, G.; Font-Bardía, M.; Calvet, T.; López, C. Synthesis, Characterization, Solution Behavior and Theoretical Studies of Pd(II) Allyl Complexes with 2-Phenyl-3H-indoles as Ligands. Catalysts 2019, 9, 811.

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