Insertion Reactions of CO into the Rhenium−Nitrogen Bond. η2-Carbamoyl Complexes and Their Reactions

Abstract

Deprotonation of [(CO)2RReNH(CH3)CH2CH2(η5-C5H4)]+X- (R = CO2Me, CO2Et; X = Br) followed by heating under a CO atmosphere yields the corresponding CO insertion compound (CO)2RReC(O)N(CH3)CH2CH2(η5-C5H4). An anologous insertion reaction proceeds more rapidly for the complexes [(CO)2XReNH(CH3)CH2CH2(η5-C5H4)]+Y- (X = Br, I, PhS, and PhSe) in which X is a strong electron-withdrawing group. Without the presence of external ligands, the oxygen of the resultant carbamoyl group binds to the rhenium to fulfill the 18-electron rule. The η2-carbamoyl selenolate complex [(CO)PhSeRe(η2-CO)N(CH3)CH2CH2(η5-C5H4)] (9b) has been characterized by X-ray crystallography. Upon addition of two-electron-donor ligands, such as CO, isocyanides, and trialkyl phosphites, the η2-carbamoyl complexes convert cleanly to the corresponding η1-carbamoyl complexes.