A variety of chemical transformations benefit from the use of strong electron-donating ancillary ligands, such as alkylphosphines or N-heterocyclic carbenes when electron-rich metal centers are required. Herein, we describe a facile and highly modular access to monodentate and bidentate imidazolin-2-ylidenamino-substituted phosphines. Evaluation of the phosphine's electronic properties substantiate that the formal replacement of alkyl or aryl groups by imidazolin-2-ylidenamino groups dramatically enhance their donor ability beyond that of alkylphosphines and even N-heterocyclic carbenes. The new phosphines have been coordinated onto palladium(II) centers, and the beneficial effect of the novel substitution patterns has been explored by using the corresponding complexes in the palladium-catalyzed Suzuki-Miyaura cross-coupling reaction of non-activated aryl chloride substrates.

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The synthesis and properties of a series of strongly electron-donating, sterically demanding dialkyl(1,3-diarylimidazolin-2ylidenamino)phosphines (IAPs) are reported. Determination of the TEP values shows that the bulky IAPs are better donor ligands than classical N-heterocyclic carbenes. The steric profiles of the IAPs in neutral and cationic gold(I) complexes were analyzed by X-ray diffraction studies and computational methods, revealing similar structural features to the Buchwald-type phosphines. The new phosphines were tested in the gold-catalyzed hydroamination of phenylacetylene with anilines.

Oxophosphonium ions (R P=O) are fascinating chemical intermediates related to the well-known acylium cations (RC=O) , and comprise a tricoordinate phosphorus(V) center with a phosphorus-oxygen double bond. Here, we report the synthesis of two oxophosphonium ions stabilized by bulky imidazolin-2-imine and imidazolin-2-olefin substituents attached to phosphorus. The novel species were characterized by NMR spectroscopy and single-crystal X-ray diffraction analysis, and the bonding situation was probed by DFT calculations. Determination of the acceptor number and the fluoride ion affinity revealed that the choice of the substituents has a strong influence on the electrophilicity of the phosphorus center. Additionally, the formation of Lewis base adducts with pyridine derivatives and the reactivity with isopropyl alcohol was explored.

Eine Vielzahl chemischer Umwandlungen, bei denen elektronenreiche Metallzentren benötigt werden, profitiert vom Einsatz stark elektronendonierender Hilfsliganden wie Alkylphosphane oder N‐heterocyclische Carbene. Hier beschreiben wir einen einfachen und praktikablen Zugang zu ein‐ und zweizähnigen Imidazolin‐2‐ylidenamino‐substituierten Phosphanen. Die Evaluierung der elektronischen Eigenschaften belegt, dass durch den formalen Austausch von Alkyl‐ oder Arylgruppen gegen Imidazolin‐2‐ylidenamino‐Gruppen die Donorstärke dieser Phosphane weit über die der Alkylphosphane und sogar N‐heterocyclischer Carbene erhöht werden kann. Palladium(II)‐Komplexe dieser Phosphanliganden wurden synthetisiert, und der Einfluss des neuen Substitutionsmusters in palladiumkatalysierten Suzuki‐Miyaura‐Kreuzkupplungen von nichtaktivierten Arylchloriden wurde untersucht.