Search results for "ion chemistry"
showing 10 items of 254 documents
The Taming of Redox‐Labile Phosphidotitanocene Cations
2019
International audience; Tame d0 phosphidotitanocene cations stabilized with a pendant tertiary phosphane arm are reported. These compounds were obtained by one-electron oxidation of d1 precursors with [Cp2Fe][BPh4]. The electronic structure of these compounds was studied experimentally (EPR, UV/Vis, and NMR spectroscopy, X-ray diffraction analysis) and through DFT calculations. The theoretical analysis of the bonding situation by using the electron localization function (ELF) shows the presence of π-interactions between the phosphido ligand and Ti in the d0 complexes, whereas dπ–pπ repulsion prevents such interactions in the d1 complexes. In addition, CH–π interactions were observed in seve…
Phosphasalen group IV metal complexes: synthesis, characterization and ring opening polymerization of lactide.
2020
International audience; We report the synthesis of a series of Zr and Ti complexes bearing phosphasalen which differs from salen by the incorporation of two P atoms in the ligand backbone. The reaction of phosphasalen proligands (1a-1c)H2 with Zr(CH2Ph)4 led to different products depending on the nature of the N,N-linker in the ligand. In case of ethylene-linked phosphasalen, octahedral Zr complex 2a formed as a single stereoisomer in trans geometry. With the phenylene linker, it was shown by dynamic NMR spectroscopy that complex 2b exists as a mixture of trans and cis-β isomers in solution, both enantiomers (Δ and Λ) of the cis-β isomer being in fast equilibrium with respect to the NMR tim…
First copper(I) ferrocenyltetraphosphine complexes: possible involvement in Sonogashira cross-coupling reaction ?
2008
Preparation and characterization of the first examples of copper(I) ferrocenylpolyphosphine complexes are reported. The molecular structure of complex {P,P′,P′′-[1,1′,2,2′-tetrakis(diphenylphosphino)-4,4′-di-tert-butylferrocene]iodocopper(I)} (1) was solved by X-ray diffraction studies, and its fluxional behavior in solution was investigated by VT-31P NMR; both revealed a net triligated coordination preference of the ferrocenyl tetraphosphine Fc(P)4tBu with copper. The tetradentate ligand is an active auxiliary in Sonogashira alkynylation; therefore the general question of copper as a competitive coordination partner in the Pd/Cu-catalyzed Sonogashira reaction was raised and discussed. Elec…
Computational study of the spin-forbidden H 2 oxidative addition to 16-electron Fe(0) complexes
2003
International audience; The spin-forbidden oxidative addition of H2 to Fe(CO)4, Fe(PH3)4, Fe(dpe)2 and Fe(dmpe)2 [dpe = H2PCH2CH2PH2, dmpe = (CH3)2PCH2CH2P(CH3)2] has been investigated by density functional theory using a modified B3PW91 functional. All 16-electron fragments are found to adopt a spin triplet ground state. The H2 addition involves a spin crossover in the reagents region of configurational space, at a significantly higher energy relative to the triplet dissociation asymptote and, for the case of Fe(CO)4·H2, even higher than the singlet dissociation asymptote. After crossing to the singlet surface, the addition proceeds directly to the classical cis-dihydride product. Only for…
Electrochemical, Spectroelectrochemical, and Structural Studies of Mono- and Diphosphorylated Zinc Porphyrins and Their Self-Assemblies
2019
International audience; Three series of porphyrins containing a Zn(II) central metal ion and zero, one or two phosphoryl groups at the meso-positions of the macrocycle were characterized as to their electrochemical, spectroscopic and structural properties in non-aqueous media. The investigated compounds are represented as 5,15-bis(4'-R-phenyl)porphyrinatozinc, 10-(diethoxyphosphoryl)-5,15-bis(4'-R-phenyl)porphyrinatozinc and 5,15-bis(diethoxyphosphoryl)-10,20-bis(4'-R-phenyl)porphyrinatozinc, where R = OMe, Me, H or CN. Linear-free energy relationships are observed between the measured redox potentials at room temperature and the electronic nature of the substituents at the 5 and 15 meso-ph…
NMR T1-Relaxation Measurements on Paramagnetic Organolanthanides: An Alternative Tool for Structure Determination in Solution
2005
1H NMR investigations were conducted on four paramagnetic organolanthanides, all bearing the tetraisopropylcyclopentadienyl ligand Cp4i (HC5iPr4) in order to verify whether or not interactions observed in the solid state are maintained in solution. In some cases variable-temperature experiments were necessary to enhance the resolution and determine the best conditions for the study. The 1D NMR spectrum could be interpreted in every case. Complementary 2D COSY experiments allowed the full attribution of the signals. T1 (1H) relaxation values were determined for all the paramagnetic complexes at the most suitable temperature, and compared with those of the diamagnetic KCp4i. The same tendency…
Structural, photophysical and magnetic properties of transition metal complexes based on the dipicolylamino-chloro-1,2,4,5-tetrazine ligand
2015
International audience; The ligand 3-chloro-6-dipicolylamino-1,2,4,5-tetrazine (Cl-TTZ-dipica) 1, prepared by the direct reaction between 3,6-dichloro-1,2,4,5-tetrazine and di(2-picolyl)-amine, afforded a series of four neutral transition metal complexes formulated as [Cl-TTZ-dipica-MCl2]2, with M = Zn(II), Cd(II), Mn(II) and Co(II), when reacted with the corresponding metal chlorides. The dinuclear structure of the isostructural complexes was disclosed by single crystal X-ray analysis, clearly indicating the formation of [MII–(μ-Cl)2MII] motifs and the involvement of the amino nitrogen atom in semi-coordination with the metal centers, thus leading to distorted octahedral coordination geome…
Unsymmetrically Substituted Bis(phosphino)Ferrocenes Triggering Through-Space 31(P, P′)-Nuclear Spin Couplings and Encapsulating Coinage Metal Cations
2021
International audience; We describe unsymmetrically substituted di-tert-butylated 1,1'-bis(phosphino)ferrocenes, with phosphino substituents R = [5-methyl]-2-furyl = Fu, and R' = phenyl (4a), i-propyl (4b). A modular synthetic approach was applied from the di-tert-butylated ferrocene platform (1), which lead to the formation of new diphosphines by using 1,1'bis(diiodo)-3,3'-bis(tert-butyl)ferrocene (2) as synthetic precursor. In contrast to the cousin non-alkylated unsymmetrically substituted diphosphino-ferrocenes which were reported up to now, these diphosphines showed strong (31 P, P')nonbonded (" ug-p e") nuclear spin-spin coupling. The strength of such internuclear spin-spin coupling c…
Theoretical Investigation of the Low-Energy States of CpMoCl(PMe 3 ) 2 and Their Role in the Spin-Forbidden Addition of N 2 and CO
2003
International audience; A recent computational investigation of Jahn−Teller effects in unsaturated 16-electron d4d6 [CpMLn] complexes (Abu-Hasanayn, F.; Cheong, P.; Oliff, M. Angew. Chem.2002, 41, 2120) highlighted the typical presence of two spin-triplet and two singlet states of competing stability in these complexes and pointed out the necessity to account for more than one electronic state in studies thereof. Consequently, we have reinvestigated the addition of N2 to all the four low-energy states of CpMoCl(PH3)2, a reaction for which previously only one singlet and one triplet state have been considered (Keogh, D. W.; Poli, R. J. Am. Chem. Soc.1997, 119, 2516). The present study was pe…
Supramolecular open-framework architectures based on dicarboxylate H-bond acceptors and polytopic cations with three/four N–H+donor units
2015
International audience; Supramolecular assemblages based on anionic H-acceptors and cationic H-donors have been envisioned to elaborate open frameworks maintained by ionic H-bonds. Combinations of di-anionic chloranilate (CA2-), oxalate (Ox2-), or terephthalate (BDC2-) and trisimidazolium or tetrapyridinium derivatives (three and four N-H+ donors, respectively) yielded five architectures of formulae [(H3TrIB)(CA)1.5[middle dot]2DMF[middle dot]2.5H2O] (1), [(H4Tetrapy)(CA)2[middle dot]3DMF] (2), [(H3TrIB)(HOx)(Ox)[middle dot]5H2O] (3), [(H4Tetrapy)(Ox)2[middle dot]5H2O] (4), and [(H4Tetrapy)(BDC)2(H2O)[middle dot]1DMF[middle dot]3H2O] (5) (with TrIB = 1,3,5-trisimidazolylbenzene and Tetrapy …