The first stable rhodium complex having a beta-ketophosphenato ligand, which is a heavier congener of a beta-ketoiminato ligand, has been synthesized and characterized. Comparison of properties between rhodium beta-ketophosphenates 2 and rhodium beta-ketoiminate 4 revealed the unique character of the beta-ketophosphenato ligand, where the trans influence of the phosphorus atom should be stronger than the nitrogen atom of the beta-ketoiminato ligand.