How Rhodium(I)-Catalyzed Phosphorus(III)-Directed C–H Bond Functionalizations Can Improve the Catalytic Activities of Phosphines

Trivalent-phosphorus-containing molecules are widely used in fields ranging from catalysis to materials science. Efficient catalytic methods for their modifications, providing straightforward access to novel hybrid structures with superior catalytic activities, are highly desired to facilitate reaction improvement or discovery. We have recently developed new methods for synthesizing polyfunctional phosphines by C–C cross-couplings through rhodium-catalyzed C–H bond activation. These methods use a native P(III) atom as a directing group, and can be used in regioselective late-stage functionalization of phosphine ligands. Interestingly, some of the modified phosphines outperform their parents in Pd-catalyzed cross-coupling reactions.1 Introduction2 Early Examples of Transition-Metal-Catalyzed P(III)-Directed C–H Bond Activation/Functionalizations3 Synthesis of Polyfunctional Biarylphosphines by Late-Stage Alkylation: Application in Carboxylation Reactions4 Synthesis of Polyfunctional Biarylphosphines by Late-Stage Alkenylation: Application in Amidation Reactions5 Conclusion

Oxygen Bridged Bimetallic [Cu-O-Se] Catalyst for Sonogashira Cross-Coupling.

Most of the non-palladium catalyst employed for Sonogashira cross-coupling works with high temperature 120-140 oC and well defined ligands. Palladium based catalysts with bulkier and electron rich phosphine ligands are...

Dicoordinate Au(I)–Ethylene Complexes as Hydroamination Catalysts

A series of gold(I)–ethylene  complexes containing a family of bulky phosphine ligands has been prepared. The use of these sterically congested ligands is crucial to stabilize the gold(I)–ethylene bond and prevent decomposition, boosting up their catalytic performance in the highly underexplored hydroamination of ethylene. The precatalysts bearing the most sterically demanding phosphines showed excellent results reaching full conversion to the hydroaminated products under low ethylene pressure (1 bar). Kinetic analysis together with density functional theory (DFT) calculations revealed that the assistance of a second molecule of the nucleophile as a proton shuttle is preferred even when using an extremely congested cavity-shaped Au(I) complex.

Dehydrogenation of 1-Phenylethanol Catalyzed by Nickel(II)diphosphine Complexes

Catalytic efficacy of the nickel(II)-diphosphine systems in the dehydrogenation of 1-phenylethanol to acetophenone under acceptorless conditions was investigated. Steric and electronic factors of the phosphine ligands were found to play an important role in the catalysis, while the nature of the base used and the reaction conditions, viz. time, tempe rature, and stoichiometry, have also shown major influence. Based on the preliminary analysis, a homogeneous pathway, perhaps involving nickel hydride species, was proposed. Due to the gradual disintegration of the catalytic species, deterioration of catalytic activity was observed resulting into low to moderate conversions. Among the series of catalysts examined, the highest conversion of 52% was exhibited by the catalyst C4, dichloro(1,2-bis(diphenylphosphino)ethane) nickel(II) (5 mol%), when loaded with 50 mol% of sodium ethoxide in toluene at 120 °C.

Reviving the Coordination Chemistry of Sulfonium Cations

ABSTRACT: More than a century old, sulfonium ions are still intriguing species in the landscape of organic chemistry. On one hand they have found broad applications in organic synthesis and material science, but on the other hand, while isoelectronic to the ubiquitous tertiary phosphine ligands, their own coordination chemistry has been neglected for the last three decades. Here we report the synthesis and full characterization of the first Rh(I) and Pt(II) complexes of sul-fonium. Moreover, for the first time, the coordinating ability of an aromatic sulfonium has been established. A thorough computational analysis of the exceptionally short S-Rh bonds obtained attests for the strongly π-accepting nature of sul-fonium cations and places them among the best π-acceptor ligands available today. Our calculations also show that when embedded within a pincer framework their π-acidity is enhanced. Therefore, in addition to the stability and modularity that these frameworks offer, our pincer complexes might open the way for sulfonium cations to become powerful tools in π-acid catalysis.