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

The chelate complexes of the types [Rh(CO)Cl(Ph2PCH2P(Se)Ph-2)] (1) and [Rh(CO)Cl(Ph2PN(CH3)P(Se)Ph-2)] (2) have been synthesized and characterized by IR and NMR spectroscopy. The lower shift of the nu(P-Se) bands and downfield shift of the P-31-{H-1} 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 v(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 [Rh(COCH3)CII(Ph2PCH2P(Se)Ph-2)] (3) and [Rh(COCH3)CII(Ph2PN(CH3)P(Se)Ph-2)] (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)(2)I-2](-) and 2 shows higher catalytic activity compared to 1. (c) 2005 Elsevier B.V. All rights reserved.