The effect of ligand on the activity of immobilized ruthenium complexes synthesized in situ was investigated. The activity of the catalyst containing ZPh₃ ligand changed as follows: PPh₃＞AsPh₃＞NPh₃. When PPh₃ was used as ligand, the corresponding TOF of formic acid was 656 h^－1 over the catalyst. In addition, using bidentate phenyl phosphine as ligand instead of PPh₃ resulted in an even higher TOF, the value was 1190 h^－1 when dppe was used as ligand. The results of quantum chemistry theoretic calculation indicated that the PPh₃ ligand which had the moderate capability of σ-donor and π-acceptor, less steric hindrance and preferable electron delocalization, acted as a better ligand than the other ZPh₃ ligand. The bidentate phenyl phosphine ligands which had good electron delocalization and chelation acted as a better ligand than monodentate phosphine ligand.

Key words: immobilized, ligand, formic acid, Ru-based catalyst