Supramolecular bulky phosphines comprising 1,3,5-triaza-7-phosphaadamantane and Zn(salphen)s: structural features and application in hydrosilylation catalysis

International audienceThe use of the commercially available, bifunctional phosphine 1,3,5-triaza-7-phosphaadamantane (abbreviated as PN 3) in conjunction with a series of Zn(salphen) complexes leads to sterically encumbered phosphine ligands as a result of (reversible) coordinative Zn–N interactions. The solid state and solution phase behaviour of these supramolecular ligand systems have been investigated in detail and revealed their stoichiometries in the solid state observed by X-ray crystallography, and those determined in solution by NMR and UV-Vis spectroscopy. Also, upon application of these supramolecular bulky phosphines in hydrosilylation catalysis employing 1-hexene as a substrate, the catalysis data infer the presence of an active Rh species with two coordinated, bulky PN 3 /Zn(salphen) assembly units having a maximum of three Zn(salphen)s associated per PN 3 scaffold, with an excess of bulky phosphines hardly affecting the overall activity

A Supramolecular Palladium Catalyst Displaying Substrate Selectivity by Remote Control

Inspired by enzymes such as cytochrome P-450, the study of the reactivity of metalloporphyrins continues to attract major interest in the field of homogeneous catalysis. However, little is known about benefitting from the substrate-recognition properties of porphyrins containing additional, catalytically relevant active sites. Herein, such an approach is introduced by using supramolecular ligands derived from metalloporphyrins customized with rigid, palladium-coordinating nitrile groups. According to different studies (NMR and UV/Vis spectroscopy, XRD, control experiments), the supramolecular ligands are able to accommodate pyridine derivatives as substrates inside the porphyrin pocket while the reactivity occurs at the peripheral side. By simply tuning a remote metal center, different binding events result in different catalyst reactivity, and this enzyme-like feature leads to high degrees of substrate selectivity in representative palladium-catalyzed Suzuki–Miyaura reactions

Supramolecular Ligands in Gold(I) Catalysis

A supramolecular ligand-template strategy is applied to gold(I) catalysis. The supramolecular ligands, formed from a phosphoramidite backbone and two templates, display different regioselectivity in the hydroalkoxylation of allenes compared to non-supramolecular analogues. Based on these findings, the catalytic activity of gold(I) complexes could be tunable at

Catalytic Palladium Phosphination: Modular Synthesis of C1-Symmetric Biaryl-Based Diphosphines

International audienceA new family of C1-symmetric bis(diphenylphosphino)biphenyls have been prepared starting from readily available ortho,ortho′-dihalobiphenyl precursors by a palladium-catalyzed C–P coupling reaction. This process does not require the use of an additional ligand. To date, the synthesis of such diphosphines, by reaction of an intermediate biphenyldiyl dianion with ClPPh2, mainly afforded the undesired cyclic phosphafluorene derivative. So far, no synthetic pathway has been found to avoid this intramolecular reaction. Herein we report the first general and external-ligand-free palladium-catalyzed phosphination reaction that allows the synthesis of a wide variety of substituted ortho,ortho′-bis(diphenylphosphino)biphenyls. With the aim of illustrating the scope and efficiency of this methodology, we applied it to the establishment of a straightforward access to C1-symmetrical analogues of the most powerful ligands used in homogenous catalysis and extended it to more challenging substrates