Synthesis and structural characterization of metal complexes based on pyrazole/imidazolium chlorides

A series of imidzoalium salt, L . HCl, for the potentially bidentate pyrazole/N-heterocyclic carbene was synthesized. Reactions of a 2:1 mixture between L . HCl bearing bulky N-substitution and Ag2O produced Ag(L)Cl, whereas a novel compound with unique stoichiometry AgL2(AgCl)(0.5)Cl was produced from L . HCl bearing N-methyl group under identical condition. Reactions of L . HCl with NO, produced zwitterionic (PdCl3L)-Cl-11 . H. Selected structural determinations on L . HCl, Ag(L)Cl, AgL2(AgCl)(0.5)Cl, and (PdCl3L)-Cl-11 . H revealed intriguing crystal chemistry in which the less-stable gauche rotamers were obtained exclusively. A preliminary application of the zwitterionic complexes, (PdCl3L)-Cl-11 . H, in Heck Coupling reaction of aryl bromide with n-butyl acrylate shows effective activity. (C) 2004 Elsevier B.V. All rights reserved.