Abstract:
A series of ancillary directing ligands bearing O, S, N atoms were used to react with ZrCl4 to get the intermediate complexes, which showed certain diastereoselectivity when reacting with the dilithium salts of ethenebridged bis(indene). To carry out the selective synthesis, the ancillary directing ligand was firstly reacted with equal molar amount of ZrCl4 in toluene under argon overnight. The resultant suspension was transferred to the solid salts of C2H4[(η5Ind)Li]2 (molar ratio 1∶1) at 0 ℃. The reaction mixture was warmed up and stirred for 48 h at 30 ℃. Then the solvent was removed under vacuum and the residue was analyzed directly by 1HNMR spectroscopy to detect the relative amount of racC2H4(η5Ind)2ZrCl2 and mesoC2H4(η5Ind)2ZrCl2. Most of these ancillary directing ligands assisted the formation of racemic isomers, racC2H4(η5Ind)2ZrCl2, with the molar ratio of racC2H4(η5Ind)2ZrCl2 to mesoC2H4(η5Ind)2ZrCl2 as high as 74∶26. Further research demonstrated that the diastereoselectivity was significantly influenced by the structure, coordination atoms and substituents thereon of the intermediate complexes.