Triarylphosphines substituted with carboxylic and trifluoromethlyl groups have been prepared by the hydrolysis of trifluoromethyl groups using fuming sulfuric acid and boric acid. The reaction has been studied in a set of homoleptic and heteroleptic trifluoromethylated triarylphosphines and offers a new synthetic procedure for the preparation of carboxylic phosphines with a relatively simple methodology. The degree of carboxylation is modulated by the reaction conditions and is sensitive to the substitution pattern of the starting trifluoromethylated phosphines. A pH-dependent procedure based on the amphiphilic character of these phosphines was developed for their separation and purification. The electronic properties of the synthesized carboxylic-trifluoromethylated phosphines have been analyzed by 31P NMR of the corresponding selenide derivatives. Finally, the structures of two palladium complexes, containing the para and meta carboxylic-trifluoromethylated phosphines are also described, showing different dimeric structures.

The design of new electrically debondable adhesives has been an area of enormous interest for the recycling, repair, and reuse of electrical components for the last decade. However, the complexity of analyzing the debonding process under real conditions is a major obstacle for elucidating the mechanism. Here, a general mechanism for the electrical debonding of ionic acrylic adhesives based on imidazolium ionic liquids is reported. Using synchrotron‐based characterization techniques, in situ experiments mimicking real debonding conditions allowed for the first time the recording of ionic diffusion and chemical reactions during the debonding process. Diffusion of ionic species toward the electrodes triggers the debonding via electrochemical reactions at the adhesive–substrate interfaces. The selection of ionic adhesive chemistry and electrodelamination conditions will eventually determine the type of adhesive failure. A detailed understanding of the mechanism allows the development of new electrically debondable adhesives, which is crucial to promote circular economy and a more sustainable environment.

Development of competent and cost-effective materials for hydrogen evolution reaction (HER) has been attracting great attention since hydrogen is hailed as a promising environmentally friendly energy source to reduce the greenhouse emissions. Herein, Ru(0) nanoparticles (RuNPs) have been stabilized onto the surface of four different conducting carbon nanomaterials (CNMs) from 0D to 3D, such as 0D carbon nanohorns (CNH), 1D single-walled carbon nanotubes (CNTs), 2D reduced graphene oxide (rGO) and 3D graphite (GP), for their use in the photocatalytic HER. For this aim, the resulting RuNP@CNMs where physically mixed with mesoporous graphitic carbon nitride (mpg-CN) in an optimum composition ratio to maximize the photocatalytic HER activity. Notably, the resulting four hybrid RuNPs@CNM/mpg-CN materials showed an outstanding increase in the hydrogen evolution reaction (HER) when compared with the pristine mesoporous graphitic carbon nitride without co-catalyst. A comparison on the photocatalytic activity of the four hybrid RuNPs@CNMs physically mixed with mpg-CN and a deep study on the fate of the nanohybrids after catalysis are presented. (c) 2020 Elsevier Ltd. All rights reserved.

The stereoelectronic properties of a series of trifluoromethylated aromatic phosphines have been studied using different approaches. The sigma-donating capability has been evaluated by nuclear magnetic resonance (NMR) spectroscopy of the selenide derivatives and the protonated form of the different trifluoromethylated phosphines. The coupling constants between phosphorous and selenium ((1)J(SeP)) and phosphorous and hydrogen ((1)J(HP)) can be predicted by empirical equations and correlate the basicity of the phosphines with the number and relative position of trifluoromethyl groups. In contrast, the pi-acceptor character of the ligands has been evaluated by measuring the frequency of the CO vibration in the infrared (IR) spectra of the corresponding Vaska type iridium complexes ([IrCl(CO)(PAr3)(2)], PAr3=triarylphosphine). Moreover, the correlation between the electronic properties and the performance of these phosphines as ligands in the rhodium-catalysed hydroformylation of 1-octene has been established. Phosphines with the lowest basicity, that are those with the highest number of trifluoromethyl groups, gave rise to more active catalytic systems.

Micelle-like polyelectrolyte polymer particles were applied as phase transfer agents and catalyst carriers in the multiphasic hydroformylation of long chain alkenes achieving high turnover frequencies and efficient catalyst recovery.

HYPOTHESIS:Colloidal particles have been used to covalently bind ligands for the heterogenization of homogeneous catalysts. The replacement of the covalent bonds by electrostatic interactions between particles and the catalyst could preserve the selectivity of a truly homogeneous catalytic process. EXPERIMENTS:Functionalized polymer particles with trimethylammonium moieties, dispersed in water, with a hydrophobic core and a hydrophilic shell have been synthesized by emulsion polymerization and have been thoroughly characterized. The ability of the particles with different monomer compositions to act as catalyst carriers has been studied. Finally, the colloidal dispersions have been applied as phase transfer agents in the multiphasic rhodium-catalyzed hydroformylation of 1-octene. FINDINGS:The hydrodynamic radius of the particles has been shown to be around 100 nm, and a core-shell structure could be observed by atomic force microscopy. The polymer particles were proven to act as carriers for the water-soluble hydroformylation catalyst, due to electrostatic interaction between the functionalized particles bearing ammonium groups and the sulfonated ligands of the catalyst. The particles were stable under the hydroformylation conditions and the aqueous catalyst phase could be recycled three times.

The telomerization of 1,3-butadiene with acetic acid catalyzed by palladium(II) acetate associated with a series of phosphines in 3-(2-methoxyethyl)-1-methylimidazolium acetate was used to investigate the role of the ionic liquid. The ionic liquid plays multiple roles in this reaction as it acts as the solvent, stabilizer, ligand, and cocatalyst. The reaction performed in the presence of Dan2phos, a trifluoromethylated sulfonated triarylphosphine, at 100 degrees C for 24h gave a turnover number of 14600 with 89% selectivity to telomers at 75% 1,3-butadiene conversion and complete acetic acid conversion.

Trifluoromethylated and sulfonated triarylphosphines are remarkably resistant toward oxidation and very active for the biphasic hydroformylation of polar alkenes.

Enantiopure bis(diamidophosphite) ligands with a heterocyclic terminal fragment derived from (R)- and (S)-N,N'-dimethyl-1,1'-binaphthyldiamine and bridging fragments derived from (S,S)-2,3-butanediol (a), (4R,5R)-4,5-di(hydroxymethyl)-2,2-dimethyl-1,3-dioxolane (b), and (R)-and (S)-1,1'-bi-2-naphthol (c) were used to prepare the palladium complexes with general formula [Pd(eta(3)-2-CH3-C3H4)(P-P)][X] (X = PF6, 1a-(S;S-al;S-al;S), 113-(R;R-al;R-al;R), 1b-(S;R-al;R-al;S), 1c-(R;R-al;R), 1c-(R;S-al;R); X = BPh4, 2a-(R;S-al;S-al;R), 2c-(R;R-al;R)), which have been fully characterized. The solid-state structure for complexes 1a-(S;S-al;S-al;S) and 1b-(R;R-al;R-al;R) has been determined by X-ray diffraction. The catalytic performance of the palladium complexes has been evaluated in asymmetric allylic alkylation and amination reactions with the benchmark substrate. The influence of the nature and absolute configuration of both the terminal and bridging fragments of the bis(diamidophosphite) ligands on the asymmetric induction is discussed. The best results in terms of enantioselectivity were obtained with 1c-(R;R-al;R), affording enantiomeric excesses up to 85% in both alkylation and amination reactions. A large match-mismatch effect between the absolute configurations of stereocenters of ligand c has been observed in the allylic amination process. Preliminary results in the rhodiumcatalyzed asymmetric hydroformylation of styrene by using bis(diamidophosphite) ligands a, b, and c disclosed in all cases low enantiomeric discrimination for the branched aldehyde. Both for the allylic alkylation and for the hydroformylation reaction, a related monodentate diamidophosphite d, derived from (R)-N,N'-dimethyl-1,1'-binaphthyldiamine and (S)-borneol, was also tested. Palladium complexes of this monodentate ligand showed fairly good enantioselectivity in allylic alkylation, but with very low rate, while the rhodium complex of d rendered better enantioselectivity (37% ee) than the bidentate ligands a-c in the hydroformylation of styrene.

This paper reports the comparison of the chemoselectivity of two different Pd catalytic systems, namely molecular and colloidal systems, in C–C coupling reactions. For this purpose, new hybrid pyrazole derived ligands containing alkylether, alkylthioether or alkylamino moieties have been synthesized and used to form Pd(II) complexes and to stabilize Pd nanoparticles (Pd NPs). With the aim of studying the coordination mode of the ligands and further to understand their role in catalysis, both types of Pd species were characterized by appropriate techniques. In C–C coupling reactions promoted by different Pd colloidal systems, several reports evidenced that active species are molecular catalysts leached from Pd NPs. The most important feature of this work relies on the differences observed in the output of C–C coupling reactions, depending on the colloidal or molecular nature of the catalyst employed. Thus, molecular systems carry out typical Suzuki–Miyaura cross-coupling, together with the dehalogenation of the substrate in different proportions. In contrast, Pd NPs catalyze either Suzuki–Miyaura or C–C homocoupling reactions depending on the haloderivative used. Interestingly, Pd NPs catalyze the quantitative dehalogenation of 4-iodotoluene. Differences observed in the chemoselectivity of these two catalytic systems support that reactions carried out with Pd NPs stabilized with the hybrid pyrazole ligands employed here take place on the surface of the colloids.

A series of bis-BINOL-2′,2″-propyl ethers with different substituents at the propyl ether bridge, were investigated in the asymmetric titanium catalysed ethylation of arylaldehydes with Et2Zn, with conversions up to 99% and enantiomeric excesses up to 80%. Semiempirical PM6 calculations indicate that the higher ability of the unsubstituted ligand to form chelated titanium complexes could be related to its higher enantioselectivity. Catalytic experiments with partially optically enriched ligand put in evidence a negative non-linear effect (−)-NLE that suggest the presence of two ligand molecule in the active titanium species. Further catalytic data, together with 1H NMR and circular dichroism (CD) titrations of the ligand with Ti(iPrO)4, as well as ESI-MS experiments, allow to propose a trinuclear species [Ti3L2(OiPr)8] (L=dianion of (1R,1′R)-2′,2″-(propane-1,3-diyl)bis(oxy)di-1,1′-binaphthyl-2-ol) as responsible for the catalytic asymmetric addition of Et2Zn to aldehydes. This catalytic species is only formed with great Ti(OiPr)4/ligand molar ratios (ca. 8).