A series of piperidoimidazolinium salts which differ in the chain lengths (butyl, octyl, dodecyl, octadecyl) and their Pd-N-heterocyclic carbene complexes with pyridine were synthesized and characterized using elemental analysis and spectroscopic methods. The effects of these ligands on catalyst activation and the performance of the complexes were studied in Suzuki-Miyaura reactions of arylboronic acid with aryl chlorides. The complex with the ligand having the longest chain length was found to be most active. The results demonstrated that the length of the alkyl chain of the piperidoimidazolin-2-ylidene controlled the dispersion and composition of the nanoparticles and it affected the catalytic activity. The impact of alkyl chain length of piperidoimidazolin-2-ylidene on the Suzuki-Miyaura reactions of arylboronic acid with aryl halides was systematically investigated.