The paper deals with the use of an alllylphosphinite ligand for the synthesis of a new family of metallacycles, the iridaoxalaphosphalanes through nucleophilic attack of phosphanes to the allyl moiety of the ligand. Display omitted An alkenylphosphinite compound has been used to synthesize the unknown iridaoxaphospholane complexes which have been characterized in solution and solid state. The reactions took place in mild conditions and the product were obtained in good yields. The synthesis of the iridaoxaphospholane complexes is based on the capability of the alkenylphosphinite compound to behave as a κ1P or κ3(P, C, C) ligand when bonded to a metal complex. Theoretical calculations have been performed to explain the formation of the iridaoxaphospholane derivative due to a lower energy barrier for the nucleophilic attack at the terminal carbon of the olefin.