P-Modular bis(phosphines) based on the 1,2-trans-disubstituted cyclopentane framework in synthesis, coordination chemistry, and catalysis

The review describes a class of versatile bidentate phosphines having a homochiral 1,2-disubstituted cyclopentane backbone, the use of such ligands in coordination chemistry, and their application in transition metal-catalyzed synthesis, including CH activation, CC coupling, CC hydrogenation, and hydroformylation. In particular, the synthetic potential of the multi-purpose PH and PCl reagents (R,R)- and (S,S)-C₅H₈(PX₂)₂ (X = H, Cl) is highlighted, since these open up the possibility to incorporate virtually any other PO-, PN- or PC-bonded residue (“module”) into the homochiral bis(phosphine) framework. The resulting chelate ligands allow access to transition metal catalysts with stereodiscriminating properties determined by parameters such as (i) the presence of P-substituents that are equal or pairwise different in steric demand, (ii) the spatial orientation of such substituents with respect to the coordination plane of the catalyst complex, and (iii) the combination of C- and P-chirogenic stereoelements in matched (or mismatched) fashion. A comparative discussion of the crystal structures that are currently available for the free ligands and their transition metal complexes is also presented.