摘要
The reactions of ethyl-(S)-(-)-lactate with R 3 Al in diethyl ether yield the pentacoordinated complexes [R 2 Al((S)-(-)-μ 2 -OC(H)(Me)C(O)OEt))] 2 (1: R=Me; 2: R=Et; 3: R=Bu i ). These compounds have been characterized by spectroscopic studies as wells as crystallographic method. These structures show dimeric features containing unusual 5.4.5-fused rings with an Al 2 O 2 core and the ester group bonded to Al through the CO. VT NMR studies of compound 3 suggest that the weak (CO)→M dative bond may undergo dissociation in solution, giving rise to the equilibrium with a four-coordinate species among two five-coordinate species at ambient temperature.