Conversion of [(tBuCH2)2TaN]5 to Cubic TaN: Related Syntheses, EHMO Calculations, and MAS and Spin Echo 15N NMR Spectroscopies

Mark M. Banaszak Holl, Peter T. Wolczanski, Davide Proserpio, Anthony Bielecki, David B. Zax

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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).

Original languageEnglish
Pages (from-to)2468-2480
Number of pages13
JournalChemistry of Materials
Volume8
Issue number10
Publication statusPublished - 1 Oct 1996
Externally publishedYes

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