名称:
Synthesis, Structural Characterization, and Reactivity of Cp2- and (CpMe)2-Ligated Titanaaziridines and Titanaoxiranes with Fast Enantiomer Interconversion Rates
摘要:
A new synthetic route to (CpR)(2)-ligated titanaaziridines and titanaoxiranes from stable Ti(II) precursors has been developed, and the enantiomer interconversion rate constants for chiral titanaaziridines and titanaoxiranes have been measured for the first time. The titanaaziridines (CpR)(2)Ti(eta(2)-N(R-1)CHPh)(L) (R = H (10), Me (12); R-1 = Ph (a), o-anisyl (b), SiMe3 (c); L = PMe3 (a, c), -OMe (b)) and titanaoxiranes Cp2Ti(eta(2)-Ph(R)CO)(L) (R = Ph (14), H (15); L = PMe3) have been synthesized and characterized spectroscopically; titanaaziridine 10a and titanaoxirane 14 have been characterized by X-ray crystallography. The enantiomer interconversion rate constants for the chiral titanaaziridines and titanaoxiranes have been measured by variable-temperature NMR; k(inv), for 10b is the fastest enantiomer interconversion rate constant reported for any metallaaziridine or metallaoxirane to date. Titanaaziridines 10 and 12 undergo exchange reactions with C=C and C=X bonds, whereas the titanaoxiranes 14 and 15 undergo insertions.