Pyridine degradation intermediates as models for hydrodenitrogenation catalysis: Preparation and properties of a metallapyridine complex
Pyridine degradation intermediates as models for hydrodenitrogenation catalysis: Preparation and properties of a metallapyridine complex
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DOI：
10.1021/om970749r
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发表时间：
1998-02-02
期刊：
影响因子：
2.8
通讯作者：
Wigley, DE
中科院分区：
文献类型：
--
作者：
Weller, KJ;Filippov, I;Wigley, DE
本文报道了在加氢脱氮（HDN）反应模型研究过程中制备的稳定的钽金属吡啶配合物Ta（=（NCBu）-Bu-t=（CHCBu）-Bu-t=CH）OAr）（2）（THF）的制备、结构和反应。在热分解eta（2）（N，C）-吡啶络合物[eta（2）（N，C）-2，4，6-（NC 5 Bu 3 H2）-Bu-t]Ta（OAr）（2）Me（2），而当该反应在苯中进行时，分离出金属吡啶二聚体[Ta（mu-（NCBu）-Bu-t=（CHCBu）-Bu-t=CH）（OAr）（2）]（2）（6）。描述了5. THF的完整NMR表征，沿着将其转化为6.国际清算银行（吡啶）加合物Ta（=（NCBu）-Bu-t=CHC-Bu-t=CH）（OAr）（2）（py）（2）（5.py）也被描述，Ta（=（NCBu）-Bu-t=（CHCBu）-Bu-t=CH）（OAr）（2）（THF）（5.THF）与（BuNCO）-Bu-t和（PrNCNPr）-Pr-i-Pr-i反应，分别得到sigma（eta（1））和pi（eta（3））插入产物Ta[=（NCBu）-Bu-t=（CHCBu）-Bu]。t=CHC（=（NBu）-Bu-t）O]（OAr）（2）（7）和Ta[=（NCBu）-Bu-t=（CHCBu）-Bu-t=CH-（η（3）-C（=（NPr）-Pr-i）（2））]（OAr）（2）（8）。金属吡啶Ta（=（NCBu）-Bu-t=CHC-Bu-t=CH）（OAr）（2）（THF）（5.THF）的分子结构由X射线晶体学测定，表明其为三角双锥构型，氧化戊基氧和金属环碳占据赤道位置。TaNC 4金属配合物非常接近平面，并且在环周围明显存在离散的单键和双键。这种π定位明显有利于亚氨基形式Ta（=（NCBu）-Bu-t=（CHCBu）-Bu-t=CH）（OAr）（2）（THF）而不是卡宾结构。描述了这些化合物与加氢脱氮催化的相关性。
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(=(NCBu)-Bu-t=(CHCBu)-Bu-t=CH)OAr)(2)(THF) (5.THF) is isolated upon thermolyzing the eta(2)(N,C)-pyridine complex [eta(2)(N,C)-2,4,6-(NC5Bu3H2)-Bu-t]Ta(OAr)(2)Me (2) in the presence of THF, while the metallapyridine dimer [Ta(mu-(NCBu)-Bu-t=(CHCBu)-Bu-t=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(=(NCBu)-Bu-t=CHC-Bu-t=CH)(OAr)(2)(py)(2) (5.py) is also described, Ta(=(NCBu)-Bu-t=(CHCBu)-Bu-t=CH)(OAr)(2)(THF) (5.THF) is shown to react with (BuNCO)-Bu-t and (PrNCNPr)-Pr-i-Pr-i to afford the sigma (eta(1)) and pi (eta(3)) insertion products respectively Ta[=(NCBu)-Bu-t=(CHCBu)-Bu-t=CHC(=(NBu)-Bu-t)O](OAr)(2) (7) and Ta[=(NCBu)-Bu-t=(CHCBu)-Bu-t=CH-(eta(3)-C(=(NPr)-Pr-i)(2))](OAr)(2) (8). The molecular structure of the metallapyridine Ta(=(NCBu)-Bu-t=CHC-Bu-t=CH)(OAr)(2)(THF) (5.THF) was detemined by X-ray crystallography and shown to adopt a trigonal-bipyramidal configuration with amyl 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 pi localization clearly favors the imido form Ta(=(NCBu)-Bu-t=(CHCBu)-Bu-t=CH)(OAr)(2)(THF) rather than a carbene structure, The relevance of these compounds to hydrodenitrogenation catalysis is described.