900159-19-5Relevant academic research and scientific papers
Synthesis, structure, and reactivity of tantalum and tungsten homoenolate complexes
Tsurugi, Hayato,Ohno, Takashi,Yamagata, Tsuneaki,Mashima, Kazushi
, p. 3179 - 3189 (2006)
Preparation and characterization of homoenolate complexes of tantalum, Cp*Cl3Ta(CH2CR12C(=O)-OR 2) (1a: R1 = H, R2 = Et; 1b: R1 = R2 = Me; 1c: R1 = Me, R2 = C6H 4CH3-4), and tungsten, (Xyl-N=)Cl3W(CH 2CH2C(=O)OEt) (7), using zinc homoenolate reagents are described. Intramolecular coordination of the carbonyl moiety to the metal center in these complexes was confirmed by their NMR and IR spectroscopy together with X-ray analyses of 1a and 1b. The insertion reaction of isocyanide into the metal carbon bond of 1a and 7, respectively, resulted in the formation of a diazametallacycle, Cp*Cl3Ta-[N(Xyl)-C(=C=N-Xyl)-C(CH 2CH2CO2Et)=N-Xyl] (3a), which possesses a metallacyclic structure with an exocyclic ketene-imine moiety, and an η2-iminoacyl tungsten complex, (Xyl-N=)W{C(-N-Xyl)-CH 2CH2CO2Et}(CNXy])Cl3 (8). The β-proton of the homoenolate moiety of la was selectively deprotonated by KN(SiMe3)2 to afford an η4-ethyl acrylate complex, Cp*Cl2Ta(η4-ethyl acrylate) (4a). In the case of complex 1b, in which the β-positions were protected by dimethyl substituents, reaction with the dilithium salt of diazadiene afforded a tantalalactone complex, Cp*(η4-p-MeOC6H 4-DAD)Ta(CH2-CMe2C(=O)O) (5). The addition of Al(C6F5)3 to 5 afforded a novel zwitterionic complex, Cp*(p-MeOC6H4-DAD)Ta(CH2CMe 2C(=O)O-Al(C6F5)3) (6), in which Al(C6F5)3 coordinated to the exocyclic carbonyl oxygen of the tantalalactone.
