The conversion of pentamer [(tBuCH2)2TaN]5 (2) and ammonia to cubic TaN0.8 (5) proceeds via precipitate 1/n[TaC1.41H3.90N1.90]n (3) and amorphous TaN (4). Precursors other than (tBuCH2)3Ta=CHtBu (1) and NH3, which provided 2, such as Ta(NMe2)5 (7) and NH3, (Me2N)3-Ta=NtBu (9) and NH3, also afforded 5. Extended Hückel molecular orbital calculations were conducted to examine the electronic changes that appear upon oligomerization of hypothetical Me2TaN to (Me2TaN)∞, as a model for pentamer 2 formation. The relationship between pentamer 2 and the remaining nitrides, 3-5 was probed via magic angle spinning (MAS) and spin-echo solid-state 15N NMR experiments that probe the local environments of the various nitrogen atoms. In combination with 15N-labeling studies, the spin-echo spectra were used in an effort to analyze the possibility of a direct relationship between the 2-dimensional Ta2N2 "squares" of the pentamer (2) and the 3-dimensional Ta4N4 "cubes" of the ultimate product, cubic TaN0.8 (5).
Conversion of [(tBuCH2)2TaN]5 to cubic TaN: related syntheses, EHMO calculations, and MAS and spin echo 15N NMR spectroscopies / M.M. Banaszak Holl, P.T. Wolczanski, D.M. Proserpio, A. Bielecki, D.B. Zax. - In: CHEMISTRY OF MATERIALS. - ISSN 0897-4756. - 8:10(1996), pp. 2468-2480. [10.1021/cm960034z]
Conversion of [(tBuCH2)2TaN]5 to cubic TaN: related syntheses, EHMO calculations, and MAS and spin echo 15N NMR spectroscopies
D.M. Proserpio;
1996
Abstract
The conversion of pentamer [(tBuCH2)2TaN]5 (2) and ammonia to cubic TaN0.8 (5) proceeds via precipitate 1/n[TaC1.41H3.90N1.90]n (3) and amorphous TaN (4). Precursors other than (tBuCH2)3Ta=CHtBu (1) and NH3, which provided 2, such as Ta(NMe2)5 (7) and NH3, (Me2N)3-Ta=NtBu (9) and NH3, also afforded 5. Extended Hückel molecular orbital calculations were conducted to examine the electronic changes that appear upon oligomerization of hypothetical Me2TaN to (Me2TaN)∞, as a model for pentamer 2 formation. The relationship between pentamer 2 and the remaining nitrides, 3-5 was probed via magic angle spinning (MAS) and spin-echo solid-state 15N NMR experiments that probe the local environments of the various nitrogen atoms. In combination with 15N-labeling studies, the spin-echo spectra were used in an effort to analyze the possibility of a direct relationship between the 2-dimensional Ta2N2 "squares" of the pentamer (2) and the 3-dimensional Ta4N4 "cubes" of the ultimate product, cubic TaN0.8 (5).
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