Cleavage reactions of [PdBr(2)(NHC)](2) with two equiv. of pyridine derivatives (L), having one or two carboxylic acid groups [L = NC(5)H(4)-2-COOH, NC(5)H(4)-3-COOH, NC(5)H(4)-4-COOH, or NC(5)H(3)-2,6-(COOH)(2) in chloroform or DMSO, respectively, afforded the monomeric mixed ligand complexes trans-[PdBr(2)(NHC)L] (1-4) which, due to deprotonation of the carboxylic acid functionality, are water soluble in KOH. The catalytic activity of complexes 1-4 in aqueous Suzuki-Miyaura cross-coupling reactions were evaluated and compared. The dicarboxylic functionality enhances the catalyst reactivity and stability and the carboxylate derived from 4 could be easily recovered and reused for several cycles under the mild reaction conditions.

The 1,5,6,7,8,8a-hexahydroimidazo[1,5-a]pyridine, 3, was quaternized with 2-(bromomethyl-1,3,5-trimethylbenzene, 1,4-bis(bromomethyl)-2,3,5,6-tetramethylbenzene, 2,4-bis(bromomethyl)-1,3,5-trimethylbenzene, 1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene and 1,3,5-tris(bromomethyl)-2,4,6-triethylbenzene to obtain mono-, bis-and tris-imidazolinium salts (4-7) which were characterized by elemental analysis and NMR spectroscopy. In order to understand the effects of these changes on the N-substituent and how they translate to catalytic activity, these new salts (4-7) with Pd(OAc) 2 were applied as in situ catalysts for Suzuki-Miyaura and Heck-Mirozoki cross-coupling reactions of aryl chlorides and aryl bromides, respectively. The tris-imidazolinium salts (7) were found to be more efficient than the related analogs 4-6.

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