Palladium complexes with bridged and unbridged benzimidazolin-2-ylidene ligands

Abstract

Two equivalents of N, N′-dimethylbenzimidazolyl iodide ( 1) react with Pd(OAc) 2 to yield the complex cis-bis( N, N′-dimethyl-benzimidazoli-2-ylidene)diiodo palladium ( 2). The potentially bidentate ligand 1,1′-methylene-bis( N-methylbenzimidazolyl) diiodide ( 3) reacts with Pd(OAc) 2 to yield the complex [1,1-methylene-bis( N-methylbenzimidazolin-2-ylidene)]diiodo palladium ( 4) with a bidentate carbene ligand. Both complexes were characterised by 1H- and 13C-NMR spectroscopy. The X-ray crystal structures of 2 and 4 reveal that methylene-bridging of the benzimidazolin-2-ylidene ligands leads to palladium complexes with a reduced C carbene–Pd–C carbene angle (91.3(2) in 2 vs. 83.7(3)° in 4). In addition, the angles between the planes of the carbene ligands and the PdC 2I 2 plane are reduced from almost perpendicular in 2 (83.06(10) and 79.84(13)°) to 54.4(2) and 51.8(2)° in 4, while comparable bond distances in 2 and 4 are identical within experimental error.