Synthesis and Reactivity of Neutral, Zwitterionic and Cationic Pentamethylcyclopentadienyl−Tantalum−Phosphinimide Complexes

Abstract

This paper focuses on the synthesis and reactivity of Cp*Ta(V)−phosphinimide complexes. Reaction of stoichiometric mixtures of Cp*TaCl4 and phosphinimine R3PNSiMe3 affords the complexes Cp*Ta(NPR3)Cl3, R = t-Bu 1, i-Pr 2. These species are readily derivatized to the alkylated complexes Cp*Ta(NPR3)Me3, R = t-Bu3, i-Pr 4; Cp*Ta(NPt-Bu3)(CH2Ph)Cl2, 5; and Cp*Ta(NPt-Bu3)(CH2Ph)Me2, 6. Reaction with 3 equiv of BnMgCl afforded the robust alkylidene species Cp*Ta(NPR3)(CHPh)(CH2Ph), R = t-Bu 7, i-Pr 8. Reaction of 7 with MeI gives the metallacycle Cp*Ta(NPt-Bu3)(η2-CHPhCH2)(CH2Ph), 9. Alkylation of 1 and 2 with 2 equiv of EtMgCl results in formation of the complexes Cp*Ta(NPR3)(η2-C2H4)Cl, R = t-Bu 10, i-Pr 11, while further reaction of 10 with EtMgCl affords Cp*Ta(NPt-Bu3)(η2-C2H4)(CH2CH3), 12. Reaction of 1 with 1 equiv of B(C6F5)3 results in generation of the salt [Cp*Ta(NPt-Bu3)Cl2][ClB(C6F5)3], 13, while the analogous reaction with Ph3C[B(C6F5)4] affords the related salt [Cp*Ta(NPt-Bu3)Cl2][B(C6F5)4], 14. T...