The complexes [Rh(CO)Cl(2-Ph₂PC₆H₄COOMe)], 1, and trans-[Rh(CO)Cl(2-Ph₂PC₆H₄COOMe)₂], 2, have been synthesized by the reaction of the dimer [Rh(CO)₂Cl]₂ with 2 and 4 molar equivalents of 2-(diphenylphosphino)methyl benzoate. The complexes 1 and 2 show terminal ν(CO) bands at 1979 and 1949 cm⁻¹ respectively indicating high electron density at the metal centre. The molecular structure of the complex 2 has been determined by single crystal X-ray diffraction. The rhodium atom is in a square planar coordination environment with the two phosphorus atoms trans to each other; the ester carbonyl oxygen atom of the two phosphine ligands points towards the rhodium centre above and below the vacant axial sites of the planar complex. The rhodium–oxygen distances (Rh⋯O(49) 3.18 Å; Rh⋯O(19) 3.08 Å) and the angle O(19)⋯Rh⋯O(49) 179° indicate long range intramolecular secondary Rh⋯O interactions leading to a pseudo-hexacoordinated complex. The complexes 1 and 2 undergo oxidative addition (OA) reactions with CH₃I to produce acyl complexes [Rh(COCH₃)ClI(2-Ph₂PC₆H₄COOMe)], 4, and trans-[Rh(COCH₃)ClI(2-Ph₂PC₆H₄COO-Me)(2-Ph₂PC₆H₄COOMe)], 5, and the kinetics of the reactions reveal that the complex 1 undergoes faster OA reaction than that of the complex 2. The catalytic activity of the complexes 1 and 2 in the carbonylation of methanol were higher than that of the well known species [Rh(CO)₂I₂]⁻ and the complex 1 shows higher activity than 2.