Palladium(0)-Alkene Bis(triarylphosphine) Complexes as Catalyst Precursors for the Methoxycarbonylation of Styrene

The fluorous complex [Pd(0)(P{C6H4-p-SiMe2(CH2CH2C6F13)}3)2(MA)] (MA = maleic anhydride) was synthesized and characterized by its NMR spectra. Together with the nonfluorous complexes [Pd(0)(PPh3)2(alkene)] (alkene = C2H4, (NC)2CC(CN)2, NCC(H)C(H)CN, MA, or benzoquinone) these were evaluated as catalyst precursors in the methoxycarbonylation of styrene. The nonfluorous C2H4 and MA complexes gave the highest conversions (the turnover number (TON) was 120; the (average) turnover frequency (TOF) amounted to 80 h-1). The fluorous complex gave a significantly lower conversion (TON about 38; TOF 26 h-1) than its nonfluorous counterpart, which is caused by a lower stability of the fluorous complex under the reaction conditions.