Chelate-Controlled Synthesis of rac- and meso-Me2Si(3-tBu-C5H3)2ZrCl2
摘要:
The reaction of the chelated bis-amide complex Zr{PhN(CH2)(3)NPh}Cl-2(THF)(2) (2) with Li-2[Me2Si(3-Bu-t-C5H3)(2)] yields meso-Me2Si(3-Bu-t-C5H3)(2)Zr{PhN(CH2)(3)NPh} (meso-3) in > 98% yield. In contrast, the reaction of Zr{Me3SiN(CH2)(3)NSiMe3}Cl-2(THF)(2) (4) or the related mono-THF adduct Zr{Me3SiN(CH2)(3)NSiMe3}Cl-2(THF) (5) with Li-2[Me2Si(3-Bu-t-C5H3)(2)] yields rac-Me2Si(3-Bu-t-C5H3)(2)Zr{Me3SiN(CH2)(3)NSiMe3} (rac-6) in quantitative NMR yield and 89% isolated yield. X-ray crystallographic analyses show that the Zr{RN(CH2)(3)NR} chelate ring in rac-6 has a pronounced twist conformation, while that in meso-3 has a flatter, envelope conformation. It is proposed that the conformations of the Zr{RN(CH2)(3)NR} chelate rings in the stereodetermining transition states for addition of the second Cp- ring in these reactions are similar to those in the metallocene products and control the diastereoselectivity. meso-3 and rac-6 are converted to meso-Me2Si(3-Bu-t-C5H3)(2)ZrCl2 (meso-1) and rac-1, respectively, by reaction with HCl in Et2O.
Chelate-Controlled Synthesis of rac- and meso-Me2Si(3-tBu-C5H3)2ZrCl2
摘要:
The reaction of the chelated bis-amide complex Zr{PhN(CH2)(3)NPh}Cl-2(THF)(2) (2) with Li-2[Me2Si(3-Bu-t-C5H3)(2)] yields meso-Me2Si(3-Bu-t-C5H3)(2)Zr{PhN(CH2)(3)NPh} (meso-3) in > 98% yield. In contrast, the reaction of Zr{Me3SiN(CH2)(3)NSiMe3}Cl-2(THF)(2) (4) or the related mono-THF adduct Zr{Me3SiN(CH2)(3)NSiMe3}Cl-2(THF) (5) with Li-2[Me2Si(3-Bu-t-C5H3)(2)] yields rac-Me2Si(3-Bu-t-C5H3)(2)Zr{Me3SiN(CH2)(3)NSiMe3} (rac-6) in quantitative NMR yield and 89% isolated yield. X-ray crystallographic analyses show that the Zr{RN(CH2)(3)NR} chelate ring in rac-6 has a pronounced twist conformation, while that in meso-3 has a flatter, envelope conformation. It is proposed that the conformations of the Zr{RN(CH2)(3)NR} chelate rings in the stereodetermining transition states for addition of the second Cp- ring in these reactions are similar to those in the metallocene products and control the diastereoselectivity. meso-3 and rac-6 are converted to meso-Me2Si(3-Bu-t-C5H3)(2)ZrCl2 (meso-1) and rac-1, respectively, by reaction with HCl in Et2O.