TY - JOUR
T1 - Conversion of [(tBuCH2)2TaN]5 to Cubic TaN
T2 - Related Syntheses, EHMO Calculations, and MAS and Spin Echo 15N NMR Spectroscopies
AU - Banaszak Holl, Mark M.
AU - Wolczanski, Peter T.
AU - Proserpio, Davide
AU - Bielecki, Anthony
AU - Zax, David B.
PY - 1996/10/1
Y1 - 1996/10/1
N2 - 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).
AB - 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).
UR - http://www.scopus.com/inward/record.url?scp=0037617398&partnerID=8YFLogxK
M3 - Article
AN - SCOPUS:0037617398
VL - 8
SP - 2468
EP - 2480
JO - Chemistry of Materials
JF - Chemistry of Materials
SN - 0897-4756
IS - 10
ER -