Comments on the catalytic alkoxycarbonylation of alkynes

Abstract
The alkoxycarbonyl complexes Pd(Ph2Ppy)2(CO2R)(OAc) where Ph2Ppy is 2-pyridyldiphenylphosphine and R = Me 1, Et 2, i-Pr 3 have been prepared from Pd(OAc)2 and Ph2Ppy in ethanol solution under an atmosphere of CO. Increasing the CO pressure favours the formation of palladium carbonyl species. In the presence of 2 mol equivalents of CF3CO2H, the complex Pd(Ph2Ppy)2(CO2CH3)(CF3CO2) 4 is isolated from methanol. Pd(Ph2Ppy)2(CO2CH3)Cl 5 has been obtained by the reaction of Pd(Ph2Ppy)2Cl2 with NaOCH3 in the presence of CO. 1 and 5 have been crystallographicaly characterised as trans isomers, a geometry confirmed for all the complexes by 13C NMR. The reactivity of the complexes toward alkynes and propadiene has been investigated and the π-allyl complex [Pd(Ph2Ppy)23-C3H4C(CH3)CH2}][O2CCF3] 8 isolated and structurally characterised.