Bond Formation and Coupling between Germyl and Bridging Germylene Ligands in Dinuclear Palladium(I) Complexes

The dinuclear palladium(I) complexes [L(Ar2HGe)Pd(-GeAr2)(2)Pd(GeHAr2)L] (Ar=Ph, p-Tol; L=PMe3, tBuNC) contain terminal germyl and bridging germylene ligands with the experimentally observed GeGe bond lengths of 2.8263(4)angstrom (L=PMe3) and 2.928(1)angstrom (L=tBuNC), which are close to the longest GeGe bond reported to date [2.714(1)angstrom]. Significant GeGe 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 GeGe interaction, and simultaneously activates two PdGe 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.