Bond formation and coupling between germyl and bridging germylene ligands in dinuclear palladium(I) complexes

Article abstract of DOI:10.1002/anie.201411041

The dinuclear palladium(I) complexes [L-(Ar₂HGe)Pd(μ-GeAr₂)₂Pd(GeHAr₂)L] (Ar = Ph, p-Tol; L= PMe₃, tBuNC) contain terminal germyl and bridging germylene ligands with the experimentally observed Ge...Ge bond lengths of 2.8263(4) ? (L = PMe₃) and 2.928(1) ? (L = tBuNC), which are close to the longest Ge-Ge bond reported to date [2.714(1) ?]. Significant Ge...Ge interactions between the germylene and germyl ligands (PMe₃ complexes > tBuNC complexes) are supported by DFT calculations, Wiberg bond indices (WBI), and natural bond orbital (NBO) analyses. Exchanging tBuNC for PMe₃ ligands increases the Ge...Ge interaction, and simultaneously activates two Pd-Ge bonds. Adding the chelating diphosphine 1,2-bis(diethylphosphino)-ethane (depe) to the PMe₃ complexes results in the intramolecular coupling of germyl and germylene ligands followed by extrusion of a digermane.