Modification of Wilkinson’s catalyst with triphenyl phosphite: Synthesis, structure, 31P NMR and DFT study of trans-[RhCl(P(OPh)3)(PPh3)2]

The complex trans-[RhCl(P(OPh)3)(PPh3)2] (1) has been prepared and characterized by 31P NMR spectroscopy and single crystal X-ray crystallography. It was found that in the solid state there are two forms of complex 1 in the unit cell forming a cocrystal. DFT theoretical computations have confirmed the existence of the two forms and have provided evidence for the greater stability of 1 compared with Wilkinson’s catalyst, [RhCl(PPh3)3] (2), in terms of the dissociation energy of the Rh-P(PPh3) bonds. On the basis of the phosphorus chemical shifts, δ  (PPPh3PPPh3), and the results of the theoretical computations, it is suggested that the Rh-P(PPh3) bonding interactions are slightly enhanced in 1 compared with 2. A distinct difference between complexes 1 and 2, was found to be the catalytic activity of 1 in the alkylation of allyl acetate with sodium diethylmalonate, while 2 is almost catalytically inefficient.

The modified form of Wilkinson’s catalyst, trans-[RhCl(P(OPh)3)(PPh3)2] (1) has been prepared and characterized by 31P NMR spectroscopy and single crystal X-ray crystallography. Complex 1 is characterized by superior thermal stability in solution compared with Wilkinson’s catalyst and it is suggested that the result of the substitution of the trans, to the chlorine, PPh3 of Wilkinson’s catalyst by P(OPh)3 is the fine enhancement of the Rh-P(PPh3) bonding interactions.Figure optionsDownload as PowerPoint slide