文摘
Readily prepared 2-, 4- and 5-bromo-3-methyl thiazolium triflates react by oxidative substitution with M(PPh3)4 (M = Ni or Pd) to furnish five of the expected normal and abnormal cationic thiazolylidene complexes (1a, 1b, 2a, 2b, and 3b). Carbene complex formation is accompanied by a ca. 40 ppm downfield shift of the ¦Á-N carbene carbons in Pd complexes 1 and 2 in their 13C NMR spectra but the chemical shift of C(carbene) in the abnormal 3b (¦Ä 135.7) is particularly low. Crystal and molecular structures of complexes 1a, 2b, and 3b all indicate a square planar arrangement of the ligands around the central metal atoms. The new complexes catalyse Suzuki¨CMiyaura aryl coupling.