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

• Published in: Angewandte Chemie International Edition Vol. 54; no. 9; pp. 2679 - 2683
• Main Authors: Tanabe, Makoto, Omine, Shumpei, Ishikawa, Naoko, Osakada, Kohtaro, Hayashi, Yoshihiro, Kawauchi, Susumu
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 23-02-2015; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Edition: International ed. in English
• Subjects: Bonding; Bridging; bridging ligands; density functional calculations; Exchanging; Extrusion; germanium; Joining; ligand effects; Ligands; Mathematical analysis; P ligands; Terminals; bridging ligands; density functional calculations; P ligands; germanium; ligand effects
• ISSN: 1433-7851; 1521-3773
• 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) Å (L=PMe3) and 2.928(1) Å (L=tBuNC), which are close to the longest GeGe bond reported to date [2.714(1) Å]. 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.
Cooperation of two metal centers: Electron‐donating auxiliary ligands of the dipalladium(I) complexes promote coupling of the bridging germylene (GeAr2) and terminal germyl (GeAr2H) ligands. The Ge⋅⋅⋅Ge bonding interaction of the dipalladium intermediate is enhanced by an electron‐donating PMe3 ligand which activates PdGe and PdPd bonds.