N-Pyrrolyl Phosphines: Enhanced π-Acceptor Character via Carboalkoxy Substitution
摘要:
A series of 3,4-dicarboethoxy-N-pyrrolyl phosphine ligands (R2P-NC4H2(CO2Et)(2)) is described. A number of techniques, including reaction calorimetry, infrared spectroscopy, and X-ray crystallography, demonstrate that these ligands are potent pi-acceptors and that the electronic substituent parameter chi(i) for the 3,4-(EtO2C)(2)C4H2N moiety is ca. 16, placing it in a position between fluorine and chlorine.