Fluorine-Substituted Arylphosphine for an NHC-Ni(I) System, Air-Stable in a Solid State but Catalytically Active in Solution

Well-Defined NHC-Ni Complexes as Catalysts: Preparation, Structures and Mechanistic Studies in Cross-Coupling Reactions

Developmental studies are ongoing to discover a way to utilise new N-heterocyclic carbene (NHC)-Ni complexes as catalysts. Using a bulky NHC ligand, it is possible to synthesise an NHC/phosphine-mixed heteroleptic Ni(II) complex, which can serve as an excellent catalyst for various cross-coupling reactions. During the study of the reaction mechanisms using these Ni complexes, NHC-Ni(I) complexes were accidentally discovered, and it was observed that they exhibit excellent catalytic activity for cross-coupling reactions. The possibility of the presence of NHC-Ni(I) intermediates in these catalytic reaction pathways has been experimentally demonstrated. Depending on the type of reaction, dinuclear Ni(I) and mononuclear Ni(I) complexes can function as intermediates. The results of the investigation of each reaction mechanism are summarised, and the prospects are described.

A SF5 Derivative of Triphenylphosphine as an Electron-Poor Ligand Precursor for Rh and Ir Complexes

The synthesis of the triarylphosphine, P(p-C₆H₄SF₅)₃ containing a SF₅ group, has been achieved. The experimental and theoretical studies showed that P(p-C₆H₄SF₅)₃ is a weaker σ-donor when compared with other substituted triarylphosphines, which is consistent with the electron-withdrawing effect of the SF₅ moiety. The studies also revealed a moderate air stability of the phosphine. The σ-donor capabilities of P(p-C₆H₄SF₅)₃ were estimated from the phosphorus-selenium coupling constant in SeP(p-C₆H₄SF₅)₃ and by DFT calculations. The behavior of P(p-C₆H₄SF₅)₃ as ligand has been investigated by the synthesis of the iridium and rhodium complexes [MCl(COD){P(p-C₆H₄SF₅)₃}], [MCl(CO)₂{P(p-C₆H₄SF₅)₃}₂] (M = Ir, Rh), or [Rh(µ-Cl)(COE){P(p-C₆H₄SF₅)₃}]₂, and the molecular structures of [IrCl(COD){P(p-C₆H₄SF₅)₃}] and [Rh(µ-Cl)(COE){P(p-C₆H₄SF₅)₃}]₂ were determined by single X-ray diffraction. The structures revealed a slightly larger cone angle for P(p-C₆H₄SF₅)₃ when compared to other para-substituted triarylphosphines.