Rhodium(I) carbonyl complexes of mono selenium functionalized bis(diphenylphosphino)methane and bis(diphenylphosphino)amine chelating ligands and their catalytic carbonylation activity

Article abstract of DOI:10.1016/j.jorganchem.2005.11.069

The chelate complexes of the types (1) and (2) have been synthesized and characterized by IR and NMR spectroscopy. The lower shift of the ν(P-Se) bands and downfield shift of the ³¹P-{¹H}NMR signals for both P(III) and P(V) atoms in 1 and 2 compared to the corresponding free ligands indicate chelate formation through selenium donor. 1 and 2 show terminal ν(CO) bands at 1977 and 1981 cm^-1, respectively, suggesting high electron density at the metal center. The molecular structure of 2 has been determined by single-crystal X-ray diffraction. The rhodium atom is at the center of a square planar geometry having the phosphorus and selenium atoms of the chelating ligand at cis-position, one carbonyl group trans- to selenium and one chlorine atom trans- to phosphorus atom. 1 and 2 undergo oxidative addition (OA) reaction with CH₃I to produce acyl complexes (3) and (4), respectively. The kinetics of the OA reactions reveal that 1 undergoes faster reaction by about 4.5 times than 2. The catalytic activity of 1 and 2 in carbonylation of methanol was higher than that of the well known species [Rh(CO)₂I₂]^- and 2 shows higher catalytic activity compared to 1.