Highly Enantioselective Pd-Catalyzed Synthesis of P‑Stereogenic 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 carbon–phosphorus bonds. An isolated Pd­(II) complex (<b>5</b>) catalyzes the carbon–phosphorus 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-(phenyl­(<i>o</i>-tolyl)­phosphanyl)­phenyl)­urea} (<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 P‑Stereogenic 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 carbon–phosphorus bonds. An isolated Pd­(II) complex (<b>5</b>) catalyzes the carbon–phosphorus 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-(phenyl­(<i>o</i>-tolyl)­phosphanyl)­phenyl)­urea} (<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 P‑Stereogenic 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 carbon–phosphorus bonds. An isolated Pd­(II) complex (<b>5</b>) catalyzes the carbon–phosphorus 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-(phenyl­(<i>o</i>-tolyl)­phosphanyl)­phenyl)­urea} (<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

H‑Bonding Assisted Self-Assembly of Anionic and Neutral Ligand on Metal: A Comprehensive Strategy To Mimic Ditopic Ligands in Olefin Polymerization

Self-assembly of two neutral ligands on a metal to mimic bidentate ligand coordination has been frequently encountered in the recent past, but self-assembly of an anionic ligand on a metal template alongside a neutral ligand remains an elusive target. Such a self-assembly is hampered by additional complexity, wherein a highly negatively charged anion can form intermolecular hydrogen bonding with the supramolecular motif, leaving no scope for self-assembly with neutral ligand. Presented here is the self-association of anionic ligand 3-ureidobenzoic acid <b>(2a)</b> and neutral ligand 1-(3-(diphenylphosphanyl)­phenyl)­urea (<b>1a</b>) on a metal template to yield metal complex [{COO­C₆H₄­NH­(CO)­NH₂}­{Ph₂­PC₆H₄­NH­(CO)­NH₂}­PdMe­DMSO] (<b>4a</b>). The identity of <b>4a</b> was established by NMR and mass spectroscopy. Along the same lines, 3-(3-phenylureido)­benzoic acid (<b>2b</b>) and 1-(3-(diphenylphosphanyl)­phenyl)-3-phenylurea (<b>1b</b>) self-assemble on a metal template to produce palladium complex [{COO­C₆H₄­NH­(CO)­NHPh}­{Ph₂PC₆H₄­NH­(CO)­NHPh}­PdMePy] (<b>5c</b>). The existence of <b>5c</b> was confirmed by Job plot, 1–2D NMR spectroscopy, deuterium labeling, IR spectroscopy, UV–vis spectroscopy, model complex synthesis, and DFT calculations. These solution and gas phase investigations authenticated the presence of intramolecular hydrogen bonding between hydrogen’s of <b>1b</b> and carbonyl oxygen of <b>2b</b>. The generality of the supramolecular approach has been validated by preparing six complexes from four monodentate ligands, and their synthetic utility was demonstrated in ethylene polymerization. Complex <b>4a</b> was found to be the most active, leading to the production of highly branched polyethylene with a molecular weight of 55700 g/mol and melting temperature of 112 °C