Comments on the catalytic alkoxycarbonylation of alkynes

摘要

The alkoxycarbonyl complexes Pd(Ph_2Ppy)_2(CO_2R)(OAc) where Ph_2Ppy is 2-pyridyldiphenylphosphine and R = Me 1, Et 2, i-Pr 3 have been prepared from Pd (OAc)_2 and Ph_2Ppy 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 CF_3CO_2H, the complexes Pd(Ph_2Ppy)_2(CO_2CH_3)(CF_3CO_2) 4 is isolated from methanol. Pd(Ph_2Ppy)_2(CO_2CH_3)Cl 5 has been obtained by the reaction of Pd(Ph_2Ppy)_2Cl_2 with NaOCH_3 in the presence of CO. 1 and 5 have been crystallographicaly characterised as trans isomers, a geometry confirmed for all the complexes by ~(13)C NMR. The reactivity of the complexes toward alkynes and propadiene has been investigated and the #pi#-allyl complex [Pd(Ph_2Ppy)_2{#eta#~3-C_3H_4C(CH_3)=CH_2}][O_2CCF_3]8 isolated and structurally characterised.