124357-78-4Relevant academic research and scientific papers
Synthesis and structural characterization of a Meerwein-Ponndorf-Verley/Oppenauer redox intermediate at a tantalum(V) center
Strickler,Bruck,Wexler,Wigley
, p. 266 - 273 (2008/10/08)
The alkyne adducts (DIPP)3Ta(PhC≡CPh) (1) and (DIPP)3Ta(Me3SiC≡CMe) (2, DIPP = 2,6-diisopropylphenoxide) are precursors to the metallacyclic products (DIPP)3Ta(CPh=CPhCPh(Me)O) (3) and (DIPP)3Ta(C(SiMe3)=CMeCPh2O) (4) from their reactions with 1 equiv of acetophenone and benzophenone, respectively. (DIPP)3Ta(PhC≡CPh) (1) also reacts with 1 equiv of benzaldehyde to form the related metallacyclic compound (DIPP)3Ta(CPh=CPhCH(Ph)O) (5) in high yield. Excess benzaldehyde reacts with 1 and 2 to form the benzyl alkoxide complexes (DIPP)3(PhCH2O)Ta(η2-CR=CR′CPh=O) (6, R = R′ = Ph; 7, R = Me3Si, R′ = Me) with a dative bonding interaction between the ring oxygen and the tantalum (V) center. Deuterium-labeling experiments and reactivity studies of this reaction have implicated the oxophilic complex 5 as an intermediate that is capable of transferring a hydride to a weakly coordinated (probably η1, O-bound), second molecule of an aldehyde or ketone. Thus, (DIPP)3(PhCH2O)Ta(η2-CPh=CPhCPh=O) (6), (DIPP)3(CH3CH2O)Ta(η2-CPh=CPhCPh=O) (8), and (DIPP)3(CH3CH2(CH3)-CHO)Ta(η2-CPh=CPhCPh= O) (9) are formed from the reaction of 5 with benzaldehyde, acetaldehyde, and 2-butanone, respectively.
