New enantiopure palladium(II) complexes from a stereodynamic 2,2'-biphosphole ligand.

Two enantiopure palladium(II) complexes, viz. [1,1'-(butane-1,3-diyl)-3,3',4,4'-tetramethyl-5,5'-diphenyl-2,2'-biphosphole]dichloridopalladium(II) dichloromethane solvate [systematic name: dichlorido(1,2,5,10,11-pentamethyl-3,9-diphenylperhydrodicyclopenta[a,c][1,4]diphosphepine-kappa(2)P,P')palladium(II) dichloromethane solvate], [PdCl2(C28H30P2)] x CH2Cl2, have been synthesized from stereodynamic diphosphines derived from 2,2'-biphosphole through a metal kinetic dynamic resolution. In both structures, the coordination around the metal atom is square planar, with a cis arrangement of the ligands that drastically reduces the dihedral angle between the two phosphole rings compared with the free ligand. The structural determination of both enantiomers unambiguously establishes the absolute configuration of both central and axial elements of chirality of the 2,2'-biphosphole framework and indicates that the original carbon chirality of the backbone controls the chiralities of the 2,2'-biphosphole framework.