189345-45-7Relevant academic research and scientific papers
Isolation and characterization of a monomeric metallapyridine complex: Models for pyridine hydrodenitrogenation intermediates
Weller, Keith J.,Filippov, Igor,Briggs, Paula M.,Wigley, David E.
, p. 225 - 228 (1997)
We report the preparation of a stable metallapyridine complex of tantalum prepared in the course of model studies of hydrodenitrogenation reactions. Monomeric Ta(=NCtBu=CHCtBu=CH)(OAr)2(THF)(5 · THF) is isolated upon thermolyzing the η2(N,C)-pyridine complex [η2(N.C)-2,4,6-NCt5Bu3H2]Ta(OAr)2Me (2) in THF, while the metallapyridine dimer [Ta( μ - NCtBu=CH - -CtBu=CH)(OAr)2]2 (6) is isolated when this reaction is carried out in benzene. Complete NMR characterization of 5 · THF is described, along with its conversion into 6.
Pyridine degradation intermediates as models for hydrodenitrogenation catalysis: Preparation and properties of a metallapyridine complex
Weller, Keith J.,Filippov, Igor,Briggs, Paula M.,Wigley, David E.
, p. 322 - 329 (2008/10/08)
We report the preparation, structure, and reactions of a stable metallapyridine complex of tantalum prepared in the course of model studies of hydrodenitrogenation (HDN) reactions. Monomeric Ta(=NCtBu=CHCtBu=CH)(OAr)2(THF) (5·THF) is isolated upon thermolyzing the η2(N,C)-pyridine complex [η2(N,C)-2,4,6-NC5tBu3H 2]Ta(OAr)2Me (2) in the presence of THF, while the metallapyridine dimer [Ta(μ-NCtBu=CHCtBu=CH)(OAr)2]2 (6) is isolated when this reaction is carried out in benzene. Complete NMR characterization of 5·THF is described, along with its conversion into 6. The bis(pyridine) adduct Ta(=NCtBu=CHC-tBu=CH)(OAr)2(Py)2 (5·py) is also described. Ta(=NCtBu=CHCtBu=CH)(OAr)2(THF) (5·THF) is shown to react with tBuNCO and iPrNCNiPr to afford the σ(η1) and π (η3) insertion products respectively Ta[=NCtBu=CHCtBu=CHC(=NtBu)O](OAr)2 (7) and Ta[=NCtBu=CHCtBu=CH-(η3-C(=N iPr)2)](OAr)2 (8). The molecular structure of the metallapyridine Ta(=NCtBu=CHC-tBu=CH)(OAr)2(THF) (5·THF) was detemined by X-ray crystallography and shown to adopt a trigonal-bipyramidal configuration with aryl oxide oxygens and the metallacyclic carbon occupying equatorial positions. The TaNC4 metallacycle is very nearly planar, and discrete single and double bonds are evident around the ring. This π localization clearly favors the imido form T(=NCtBu=CHCtBu=CH)(OAr)2(THF) rather than a carbene structure. The relevance of these compounds to hydrodenitrogenation catalysis is described.
