41 research outputs found
Metal-organic frameworks as kinetic modulators for branched selectivity in hydroformylation.
Finding heterogeneous catalysts that are superior to homogeneous ones for selective catalytic transformations is a major challenge in catalysis. Here, we show how micropores in metal-organic frameworks (MOFs) push homogeneous catalytic reactions into kinetic regimes inaccessible under standard conditions. Such property allows branched selectivity up to 90% in the Co-catalysed hydroformylation of olefins without directing groups, not achievable with existing catalysts. This finding has a big potential in the production of aldehydes for the fine chemical industry. Monte Carlo and density functional theory simulations combined with kinetic models show that the micropores of MOFs with UMCM-1 and MOF-74 topologies increase the olefins density beyond neat conditions while partially preventing the adsorption of syngas leading to high branched selectivity. The easy experimental protocol and the chemical and structural flexibility of MOFs will attract the interest of the fine chemical industries towards the design of heterogeneous processes with exceptional selectivity
Neutral Imino-Methyl Benzenesulfonate-Ligated Pd(II) Complexes and Implications in Ethylene Polymerization
Synthesis of renewable copolyacetals with tunable degradation
Acetal metathesis copolymerization (AMCP) of renewable isohexide diacetals and aliphatic long-chain diacetals is reported and access to a small family of copolyacetals has been established. Crucial 1â2D NMR and MALDI-ToF-MS findings unambiguously confirm the existence of a copolymeric structure. In a stark contrast to the earlier reported isohexide-polyacetals, the current copolyacetals reveal very slow degradation. Hydrolytic degradation of copolyacetal pellets is extremely slow at pH 7, whereas only 30% degradation over a period of 15 d is observed in 9 m hydrochloric acid solution. GPC investigations reveal that with increasing chain-length the rate of degradation reduces, whereas copolyacetals with short-chain aliphatic segments display a faster degradation profile. The reduced rate of degradation can be attributed to the hydrophobic nature of long-chain acetal segments. In situ NMR spectroscopy reveals the existence of formates, hemiacetals, and diols as degradation products. Thus, the rate of degradation can be tuned by the judicious choice of isohexide-diacetal and linear-diacetals in a copolyacetal.publishe
Highly Enantioselective Pd-Catalyzed Synthesis of PâStereogenic Supramolecular Phosphines, Self-Assembly, and Implication
Metal-catalyzed
asymmetric addition of a secondary phosphine to
an aryl halide is one of the most efficient and reliable approaches
for the construction of enantiopure carbonâphosphorus bonds.
An isolated PdÂ(II) complex (<b>5</b>) catalyzes the carbonâphosphorus
coupling reaction between tolylphenylphosphine (<b>1a</b>) and
3-iodophenylurea (<b>2b</b>), which proceeds with an unprecedented
enantiomeric excess (ee) of 97%. The generality of the strategy has
been demonstrated by preparing a small library of a new class of P-stereogenic
phosphines with an in-built hydrogen bonding motif for the first time.
The P-stereogenic phosphines self-assemble on a metal template via
deliberately installed hydrogen-bonding motifs and mimic the bidentate
ligand coordination. Interestingly, when it was employed in asymmetric
hydrogenation, the supramolecular phosphine {1-(3-(phenylÂ(<i>o</i>-tolyl)Âphosphanyl)Âphenyl)Âurea} (<b>6b</b>) produced
the corresponding hydrogenated product with the highest enantiomeric
excess of 99% along with excellent conversion, demonstrating the potential
of these enantioenriched P-chirogenic supramolecular phosphines in
asymmetric catalysis
Highly Enantioselective Pd-Catalyzed Synthesis of PâStereogenic Supramolecular Phosphines, Self-Assembly, and Implication
Metal-catalyzed
asymmetric addition of a secondary phosphine to
an aryl halide is one of the most efficient and reliable approaches
for the construction of enantiopure carbonâphosphorus bonds.
An isolated PdÂ(II) complex (<b>5</b>) catalyzes the carbonâphosphorus
coupling reaction between tolylphenylphosphine (<b>1a</b>) and
3-iodophenylurea (<b>2b</b>), which proceeds with an unprecedented
enantiomeric excess (ee) of 97%. The generality of the strategy has
been demonstrated by preparing a small library of a new class of P-stereogenic
phosphines with an in-built hydrogen bonding motif for the first time.
The P-stereogenic phosphines self-assemble on a metal template via
deliberately installed hydrogen-bonding motifs and mimic the bidentate
ligand coordination. Interestingly, when it was employed in asymmetric
hydrogenation, the supramolecular phosphine {1-(3-(phenylÂ(<i>o</i>-tolyl)Âphosphanyl)Âphenyl)Âurea} (<b>6b</b>) produced
the corresponding hydrogenated product with the highest enantiomeric
excess of 99% along with excellent conversion, demonstrating the potential
of these enantioenriched P-chirogenic supramolecular phosphines in
asymmetric catalysis
Highly Enantioselective Pd-Catalyzed Synthesis of PâStereogenic Supramolecular Phosphines, Self-Assembly, and Implication
Metal-catalyzed
asymmetric addition of a secondary phosphine to
an aryl halide is one of the most efficient and reliable approaches
for the construction of enantiopure carbonâphosphorus bonds.
An isolated PdÂ(II) complex (<b>5</b>) catalyzes the carbonâphosphorus
coupling reaction between tolylphenylphosphine (<b>1a</b>) and
3-iodophenylurea (<b>2b</b>), which proceeds with an unprecedented
enantiomeric excess (ee) of 97%. The generality of the strategy has
been demonstrated by preparing a small library of a new class of P-stereogenic
phosphines with an in-built hydrogen bonding motif for the first time.
The P-stereogenic phosphines self-assemble on a metal template via
deliberately installed hydrogen-bonding motifs and mimic the bidentate
ligand coordination. Interestingly, when it was employed in asymmetric
hydrogenation, the supramolecular phosphine {1-(3-(phenylÂ(<i>o</i>-tolyl)Âphosphanyl)Âphenyl)Âurea} (<b>6b</b>) produced
the corresponding hydrogenated product with the highest enantiomeric
excess of 99% along with excellent conversion, demonstrating the potential
of these enantioenriched P-chirogenic supramolecular phosphines in
asymmetric catalysis
Synthesis of meta-substituted monodentate phosphinite ligands and implication in hydroformylation â
Insertion Copolymerization of Difunctional Polar Vinyl Monomers with Ethylene
A single-step
synthesis, structural characterization and application
of a neutral, acetonitrile ligated, palladiumâphosphinesulfonate
complex [{P<sup>â§</sup>O}ÂPdMeÂ(L)] (P<sup>â§</sup>O =
Îș<sup>2</sup>-P,OâAr<sub>2</sub><i>P</i>C<sub>6</sub>H<sub>4</sub>SO<sub>2</sub><i>O</i> with Ar = 2-MeOC<sub>6</sub>H<sub>4</sub>; L = CH<sub>3</sub>CN) (<b>3</b>) in coordination/insertion
copolymerization of ethylene with difunctional olefin is investigated.
In a significant development, complex <b>3</b> was found to
catalyze insertion copolymerization of industrially relevant 1,1-disubstituted
difunctional vinyl monomers for the first time. Thus, insertion copolymerization
of ethyl-2-cyanoacrylate (ECA or super glue) and trifluoromethyl acrylic
acid (TFMAA) with ethylene produced the corresponding copolymers with
6.5% ECA and 3% TFMAA incorporation. Increasing the concentration
of difunctional olefins led to higher incorporation but at the expense
of lower activities. These observations indicate that complex <b>3</b> tolerates difunctional vinyl monomers and provides direct
access to difunctional polyolefins that have not been attempted before