Search results for "bond activation"
showing 7 items of 7 documents
Reversible O–H bond activation by an intramolecular frustrated Lewis pair
2019
The interactions of the O-H bonds in alcohols, water and phenol with dimethylxanthene-derived frustrated Lewis pairs (FLPs) have been probed. Within the constraints of this backbone framework, the preference for adduct formation or O-H bond cleavage to give the corresponding zwitterion is largely determined by pKa considerations. In the case of the PPh2/B(C6F5)2 system and p-tBuC6H4OH, an equilibrium is established between the two isomeric forms which allows the thermodynamic parameters associated with zwitterion formation via O-H bond cleavage to be probed.
Favoring alkane primary carbon-hydrogen bond functionalization in supercritical carbon dioxide as reaction medium
2019
The selectivity of a catalytic alkane functionalization process can be modified just changing the reaction medium from neat alkane to supercritical carbon dioxide (scCO2). A silica supported copper complex bearing an Nheterocyclic carbene ligand promotes the functionalization of carbon-hydrogen bonds of alkanes by transferring the CHCO2Et group from N2=CHCO2Et (ethyl diazoacetate, EDA). In neat hexane only 3% of the primary C-H bonds (ethyl heptanoate being the product) are functionalized in that manner, whereas the same reaction carried out in scCO2 provides a 30% yield in this linear ester. Such effect seems to be induced by an electronic density flux from the NHC ligand to the surroundin…
Chemistry and reactivity of dinuclear manganese oxamate complexes: Aerobic catechol oxidation catalyzed by high-valent bis(oxo)-bridged dimanganese(I…
2006
[EN] The high-valent bis(oxo)-bridged dimanganese(IV) complexes with the series of binucleating 4.5-X-2-o-phenylenebis(oxamate) ligands (opbaX(2); X = H, Cl, Me) (1a-c) have been synthesized and characterized structurally, spectroscopically and magnetically. Complexes la-c possess unique Mn-2(mu-O)(2) core structures with two o-phenylenediamidate type additional bridges which lead to exceptionally short Mn-Mn distances (2.63-2.65 angstrom) and fairly bent Mn-O-Mn angles (94.1 degrees-94.6 degrees). The cyclovoltammograms of la-c in acetonitrile (25 degrees C, 0.1 M Bu4NPF6) show an irreversible one-electron oxidation peak at moderately high anodic potentials (E-ap = 0.50-0.85 V versus SCE),…
Ammonia Activation by a Nickel NCN-Pincer Complex featuring a Non-Innocent N-Heterocyclic Carbene: Ammine and Amido Complexes in Equilibrium
2015
A Ni0-NCN pincer complex featuring a six-membered N-heterocyclic carbene (NHC) central platform and amidine pendant arms was synthesized by deprotonation of its NiII precursor. It retained chloride in the square-planar coordination sphere of nickel and was expected to be highly susceptible to oxidative addition reactions. The Ni0 complex rapidly activated ammonia at room temperature, in a ligand-assisted process where the carbene carbon atom played the unprecedented role of proton acceptor. For the first time, the coordinated (ammine) and activated (amido) species were observed together in solution, in a solvent-dependent equilibrium. A structural analysis of the Ni complexes provided insig…
Chemistry and reactivity of mononuclear manganese oxamate complexes: Oxidative carbon-carbon bond cleavage of vic-diols by dioxygen and aldehydes cat…
2006
[EN] Two new mononuclear octahedral manganese(III) complexes with the tetradentate equatorial ligand o-phenylenebis(oxamate) (opba) and two aquo (1a) or two pyridine (1b) axial ligands have been synthesized and characterized structurally, magnetically, and electrochemically. The cyclovoltammogram of 1a in acetonitrile (25 degrees C, 0.1 M Bu4NPF6) shows an irreversible one-electron oxidation peak at a high anodic potential (E-ap = 1.03 V versus SCE), while that of 1b shows two well-separated one-electron oxidation peaks at moderate to high anodic potentials (E-ap = 0.92 and 1.27 V versus SCE), the first redox-wave being quasireversible in nature. The access to formally high-valent Mn-IV and…
Reversible O-H bond activation by an intramolecular frustrated Lewis pair
2019
The interactions of the O–H bonds in alcohols, water and phenol with dimethylxanthene-derived frustrated Lewis pairs (FLPs) have been probed. Within the constraints of this backbone framework, the preference for adduct formation or O–H bond cleavage to give the corresponding zwitterion is largely determined by pKa considerations. In the case of the PPh2/B(C6F5)2 system and p-tBuC6H4OH, an equilibrium is established between the two isomeric forms which allows the thermodynamic parameters associated with zwitterion formation via O–H bond cleavage to be probed. peerReviewed
[60]Fullerene l -Amino Acids and Peptides: Synthesis under Phase-Transfer Catalysis Using a Phosphine–Borane Linker. Electrochemical Behavior
2017
International audience; A new method to link amino acid and peptide derivatives to [60]fullerene is described. It uses hydrophosphination with a secondary phosphine borane. First, the stereoselective synthesis of secondary phosphine borane amino acid derivatives was achieved by alkylation of phenylphosphine borane with gamma-iodo-alpha-amino ester reagents under phase transfer catalysis (PTC). Second, a sec-phosphine borane amino ester was saponified and coupled with alpha,gamma-diamino esters to afford the corresponding dipeptide derivatives in good yields. Finally, the hydrophosphination reaction of [60]fullerene by the sec-phosphine borane compounds was performed under PTC to obtain C-60…