Synthesis and catalytic activity of perfluoroalkylated pyridine–palladium(II) complex toward olefin hydrogenation in scCO 2 and conventional organic solvents

Abstract

The perfluoroalkylated pyridine, ( o-COOCH 2(CF 2) 7CF 3-NC 5H 4), has been synthesized in two step from nicotinic acid and then the title compound, [Pd( o-COOCH 2-(CF 2) 7CF 3-NC 5H 4) 2(OAc) 2], obtained by reaction with Pd(OAc) 2. The catalytic activity of the Pd(II) complex examined for hydrogenation of styrene, 1-octene, t-2-octene and cyclohexene for both in supercritical carbon dioxide and in organic solvents. The effect of temperature and dihydrogen pressure, as well as the influence of the palladium and substrate concentrations have been studied ( T = 320–353 K, p(H 2) 6–30 bar, [Pd] = (1.12–2.62) × 10 −5 M, [Styrene] = (8.70–34.8) × 10 −3 M). The experimentally determined rate law is r = k cat [Pd] a [Styrene] b p(H 2) c ( a = 1, b = 1 and c = 0.14) where k cat = 4.4 × 10 −2 (mol −1 l s −1) at 320 K. Activation parameters have been calculated at 320 K. Supercritical carbon dioxide is a more effective, green reaction medium for olefin hydrogenation compared with conventional organic solvents.