1063819-25-9Relevant articles and documents
PEPPSI-type palladium complexes containing basic 1,2,3-triazolylidene ligands and their role in Suzuki-Miyaura catalysis
Canseco-Gonzalez, Daniel,Gniewek, Andrzej,Szulmanowicz, Michal,Mueller-Bunz, Helge,Trzeciak, Anna M.,Albrecht, Martin
, p. 6055 - 6062 (2012)
A series of PEPPSI-type palladium(II) complexes was synthesized that contain 3-chloropyridine as an easily removable ligand and a triazolylidene as a strongly donating mesoionic spectator ligand. Catalytic tests in Suzuki-Miyaura cross-coupling reactions revealed the activity of these complexes towards aryl bromides and aryl chlorides at moderate temperatures (50 °C). However, the impact of steric shielding was the inverse of that observed with related normal Nheterocyclic carbenes (imidazol-2-ylidenes) and sterically congested mesityl substituents induced lower activity than small alkyl groups. Mechanistic investigations, including mercury poisoning experiments, TEM analyses, and ESI mass spectrometry, provide evidence for ligand dissociation and the formation of nanoparticles as a catalyst resting state. These heterogeneous particles provide a reservoir for soluble palladium atoms or clusters as operationally homogeneous catalysts for the arylation of aryl halides. Clearly, the substitution of a normal N-heterocyclic carbene for a more basic triazolylidene ligand in the precatalyst has a profound impact on the mode of action of the catalytic system. Copyright
1,2,3-Triazolylidenes as versatile abnormal carbene ligands for late transition metals
Mathew, Paulson,Neels, Antonia,Albrecht, Martin
supporting information; experimental part, p. 13534 - 13535 (2009/02/06)
The [3 + 2] cycloaddition of azides and acetylenes followed by nitrogen quaternization was applied for the generation of novel and highly modular triazolium salts. The selective substitution of the 1,3,4-substitution pattern presets such salts as precursors for a new class of abnormal carbene ligands, thus expanding the family of these high-impact ligands. Metalation of the triazolium salts is highly versatile and is illustrated by direct C-H bond activation as well as by applying a transmetalation protocol, thus providing access to Pd(II), Ru(II), Rh(I), and Ir(I) abnormal carbene complexes. The donor properties of these carbenes were analyzed by using Tolman electronic parameters and were found to be slightly stronger than those the most basic normal carbenes. Copyright
