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首页> 外文期刊>Chemistry: A European journal >Hydrogenolysis of Cycloakanes on a Tantalum Hydride Complex Supported on Silica and Insight into the Deactivatio Pathway by the Combined Use of 1D Solid-Satate NMR and EXAFS Spectroscopies
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Hydrogenolysis of Cycloakanes on a Tantalum Hydride Complex Supported on Silica and Insight into the Deactivatio Pathway by the Combined Use of 1D Solid-Satate NMR and EXAFS Spectroscopies

机译：一维固溶核磁共振和EXAFS光谱学结合使用在硅胶上负载的氢化钽络合物上环芳烃的氢解和减活途径的认识

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Hydrogenolysis of cyclic alkanes is catalysed by [(ident to SiO)_2Ta-H] (1) at 160 deg C and leads to lower alkanes and cyclic alkanes including cyclopentane. The turnover number is correlated with the number of carbon atoms of the cyclic alkanes, and therefore while cycloheptane is readily transformed, cyclopentane does not give any product (<1%). The mechanism of ring contractionprobably involves carbene de-insertion as a key carbon-carbon bond-cleavage step. The reluctance of cyclopentane to undergo hydrogenolysis was further studied: under the reaction conditions cyclopentane reacts with 1 to give the corresponding cyclopentyl derivative [(ident to SiO)_2Ta-C_5H_9] (13), which evolves towards cyclopentadienyl derivative [(ident to SiO)_2Ta(C_5H_5)] (14) according to both solid-state NMR and EXAFS spectroscopies. This latter complex is inactive in the hydrogenolysis of alkanes, and therefore the formation of cyclopentane in the hydrogenolysis of various cyclic alkanes is probably responsible for the de-activation of the catalyst by formation of cyclopentane in the hydrogenolysis of various cyclic alkanes is probably responsible for the de-activatio of the catalyst by formation of cyclopentadienyl complexes.
机译：[[与SiO] _2Ta-H]（1）在160℃催化环状烷烃的氢解反应，生成低级烷烃和包括环戊烷在内的环状烷烃。周转数与环状烷烃的碳原子数相关，因此，尽管环庚烷易于转化，但环戊烷不产生任何产物（<1％）。环收缩的机制可能涉及卡宾去插入作为关键的碳-碳键裂解步骤。进一步研究了环戊烷不愿进行氢解的反应：在反应条件下，环戊烷与1反应生成相应的环戊基衍生物[（与SiO相同）_2Ta-C_5H_9]（13），该衍生物演变成环戊二烯基衍生物[[与SiO]相同）固态NMR和EXAFS光谱均显示_2Ta（C_5H_5）]（14）。后者的络合物​​在烷烃的氢解中是不活泼的，因此在各种环状烷烃的氢解中环戊烷的形成可能是催化剂失活的原因，而在各种环状烷烃的氢解中环戊烷的形成可能是造成催化剂失活的原因。通过形成环戊二烯基络合物使催化剂失活。

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