TY - JOUR
T1 - Well-defined surface imido amido tantalum(V) species from ammonia and silica-supported tantalum hydrides
AU - Avenier, Priscilla
AU - Lesage, Anne
AU - Taoufik, Mostafa
AU - Baudouin, Anne
AU - De Mallmann, Aimery
AU - Fiddy, Steven
AU - Vautier, Manon
AU - Veyre, Laurent
AU - Basset, Jean Marie
AU - Emsley, Lyndon
AU - Quadrelli, Elsje Alessandra
PY - 2007/1/10
Y1 - 2007/1/10
N2 - The MCM-41 supported hydrides [(≡SiO)2TaH], 1a, and [(≡=SiO)2TaH3], 1b, cleave N-H bonds of ammonia at room temperature to yield the well-defined imido amido surface complexes [(≡=SiO)2Ta-(NH)(NH2)], 2, and 2·NH 3. Additionally, the surface silanes [≡Si-H] that exist in close proximity to 1a and 1b also react with ammonia at room temperature to give the surface silylamido [≡Si-NH2]. Such reaction is tantalum assisted: surface silanes were synthesized independently and in absence of tantalum by reaction of highly strained silica, SiO2-1000, with SiH4 and no reaction with ammonia was observed. Surface-supported complexes 2, 2·NH3, and [≡Si-NH2] have been characterized by, inter alia, solid-state NMR, IR, and EXAFS and independent synthesis of [≡Si-NH2]. The NMR studies on the fully 15N-labeled samples have led to unambiguous discrimination between imido, amido, and amino resonances of 2*, 2*·15NH3, and [≡Si-15NH 2] through the combination of solid-state magic angle spinning (MAS), heteronuclear correlation (HETCOR), 2D proton double-quantum (DQ) single-quantum (SQ) correlation, and 2D proton triple-quantum (TQ) single-quantum (SQ) correlation spectra. The in situ IR monitoring of the reaction of 1a and 1b with regular NH3 and 15NH 3, and after H/D exchange has yielded the determination of all the NHx vibration and deformation modes, with their respective H/D and 14N/15N isotopic shifts. EXAFS study yielded the bond distances in 2 of 1.79(2) Å for Ta=N, 1.89(1) Å for Ta-O, and 1.98(2) Å for Ta-N.
AB - The MCM-41 supported hydrides [(≡SiO)2TaH], 1a, and [(≡=SiO)2TaH3], 1b, cleave N-H bonds of ammonia at room temperature to yield the well-defined imido amido surface complexes [(≡=SiO)2Ta-(NH)(NH2)], 2, and 2·NH 3. Additionally, the surface silanes [≡Si-H] that exist in close proximity to 1a and 1b also react with ammonia at room temperature to give the surface silylamido [≡Si-NH2]. Such reaction is tantalum assisted: surface silanes were synthesized independently and in absence of tantalum by reaction of highly strained silica, SiO2-1000, with SiH4 and no reaction with ammonia was observed. Surface-supported complexes 2, 2·NH3, and [≡Si-NH2] have been characterized by, inter alia, solid-state NMR, IR, and EXAFS and independent synthesis of [≡Si-NH2]. The NMR studies on the fully 15N-labeled samples have led to unambiguous discrimination between imido, amido, and amino resonances of 2*, 2*·15NH3, and [≡Si-15NH 2] through the combination of solid-state magic angle spinning (MAS), heteronuclear correlation (HETCOR), 2D proton double-quantum (DQ) single-quantum (SQ) correlation, and 2D proton triple-quantum (TQ) single-quantum (SQ) correlation spectra. The in situ IR monitoring of the reaction of 1a and 1b with regular NH3 and 15NH 3, and after H/D exchange has yielded the determination of all the NHx vibration and deformation modes, with their respective H/D and 14N/15N isotopic shifts. EXAFS study yielded the bond distances in 2 of 1.79(2) Å for Ta=N, 1.89(1) Å for Ta-O, and 1.98(2) Å for Ta-N.
UR - http://www.scopus.com/inward/record.url?scp=33846142530&partnerID=8YFLogxK
U2 - 10.1021/ja0666809
DO - 10.1021/ja0666809
M3 - Article
C2 - 17199297
AN - SCOPUS:33846142530
SN - 0002-7863
VL - 129
SP - 176
EP - 186
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 1
ER -