Structure, Bonding, and Reactivity of Tantalum Amides Containing o-Naphthyl- and o-Indenylphenoxide Ligation

The reaction of [Ta(NMe2)5] with the o-(2,3-dihydro-1-naphthyl)-, o-(1-naphthyl)-, and o-(inden-3-yl)phenols [HOC6H2Ar-2-But2-4,6] (Ar = C10H9 (1), C10H7 (Np; 2), C9H7 (3)) has been investigated. In all three cases initial displacement of 1 equiv of dimethylamine occurs, yielding mono(aryloxides) [(ArO)Ta(NMe2)4]. Structural studies of the o-(2,3-dihydro-1-naphthyl) and o-(1-naphthyl) compounds 4 and 5 show they both adopt geometries best described as square pyramidal with an apical dimethylamido ligand and basal aryloxide oxygen. The Ta−O−Ar angles are 162° in both compounds, with no metal interaction with the ortho substituents. Compound 4 reacts with 2,3,5,6-tetraphenylphenol to form the corresponding bis(aryloxide) 6. The intermediate o-(inden-3-yl)phenoxide [(ArO)Ta(NMe2)4] 7 thermally eliminates a further 1 equiv of HNMe2 with formation of the tris(amido) compound [Ta(OC6H2{η1-Ind}-2-But-4,6)(NMe2)3] 8. The coordination geometry about tantalum in 8 is best described as trigonal bipyramidal, with an ...