Phosphine ligands based on the ferrocenyl platform: Advances in catalytic cross-couplings

Ferrocenyl skeletons tagged with a variety of donor atoms (metalloligands) have become popular in modern metal-catalyzed organic transformations, broadening the applications. Ferrocenylphosphines, such as 1′-bis(diphenylphosphino)ferrocene (dppf), have been widely used as metalloligands in academic and industrial research, motivating further investigation into novel ferrocenylphosphine ligands. The current review concentrated non-exhaustively on emblematic applications of different ferrocenylphosphine ligands in transition metal-catalyzed cross-coupling strategies. Initially, the stereochemical aspects of the ferrocenyl skeleton, nomenclature, and applications of chiral ferrocenyl phosphines in asymmetric synthesis are evoked. We simply classified ferrocenyl phosphine ligands, eventually further functionalized at cyclopentadienyl (Cp) ring, into three types based on the number of phosphine donors on the ferrocenyl backbone: monophosphine, bisphosphine, and polyphosphine ferrocenyl ligands. Furthermore, the use of hybrid monophosphinoferrocene type scaffolds (P, N)–, (P, O)–, (P, S–), (P, NHC)–, and (P, X)– (X is polar/hydrophilic like guanidium) in cross-coupling is evoked. The latest advances in the chemistry of symmetric achiral di- and polyphosphine ferrocene-based ligands related to metal-catalyzed bond-forming reactions (C–C, C–N, and C–O bonds) are discussed, with a special emphasis on consolidating all important work in this area. A cumulative table is provided in the end, with a focus on compiling significant work in this field. The general structure and electronic features and effects of ferrocenylphosphine ligands on the selectivity and activity in catalysis is also briefly evoked. The literature cut-off date was in general ending of 2020.