Heterogeneous dehydrocoupling of amine-borane adducts by skeletal nickel catalysts.
Heterogeneous dehydrocoupling of amine-borane adducts by skeletal nickel catalysts.
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DOI：
10.1021/ic201809g
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发表时间：
2011-11
影响因子：
4.6
通讯作者：
A. Robertson;Riccardo Suter;L. Chabanne;G. Whittell;I. Manners
中科院分区：
文献类型：
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作者：
A. Robertson;Riccardo Suter;L. Chabanne;G. Whittell;I. Manners
从Ni/Al合金中选择性浸出Al制得的SkalumNi已成功地用于各种胺-硼烷加合物的催化脱氢。低成本和简单的单步合成的组合使得该系统成为先前描述的贵金属和其它第一行金属催化剂的潜在有吸引力的替代物。该催化剂的多相性质有利于方便的产物纯化，并且这是第一个基于第一行过渡金属的此类系统。在20 °C下，使用5mol%骨架Ni催化剂，证明了Me（2）NH·BH（3）（1）和Et（2）NH·BH（3）（5）的催化脱氢偶联，并分别产生[Me（2）N-BH（2）]（2）（2）和[Et（2）N-BH（2）]（2）/Et（2）N-BH（2）（6）。相应的加合物iPr（2）NH·BH（3）（7）也脱氢得到iPr（2）NH·BH（2）（8），但催化剂失活严重。发现MeNH 2·BH 3的催化脱氢偶联（9）产生环状三硼氮烷[MeNH-BH 2]（3）（10）作为主要产物，而当使用化学计量量的Ni时，形成高分子量的聚（甲基氨基硼烷）[MeNH-BH 2]（n）（11）（M（w）= 78 000 Da，PDI = 1.52）。NH（3）·BH（3）（12）也观察到类似的反应性，其分别在催化和化学计量的Ni负载下产生环状低聚物和不溶性聚合物[NH（2）-BH（2）]（x）（14）。催化剂的再循环受到逐渐中毒的阻碍。对可能的催化剂毒物的研究表明，BH（3）是最有可能的表面毒物，这与以前对胶体Rh催化剂的研究一致。还探索了使用骨架Cu和Fe的胺-硼烷加合物的催化脱氢。发现Skaline Cu对于胺-硼烷加合物是活性较低的脱氢催化剂，但在化学计量条件下与MeNH（2）·BH（3）（9）反应时也产生聚（甲基氨基硼烷）。发现Skaline Fe对胺硼烷脱氢完全无活性。
Skeletal Ni, produced by the selective leaching of Al from a Ni/Al alloy, has been successfully employed in the catalytic dehydrogenation of various amine-borane adducts. The combination of low cost and facile single-step synthesis make this system a potentially attractive alternative to the previously described precious metal and other first-row metal catalysts. The heterogeneous nature of the catalyst facilitates convenient product purification, and this is the first such system to be based on a first-row transition metal. Catalytic dehydrocoupling of Me(2)NH·BH(3) (1) and Et(2)NH·BH(3) (5) was demonstrated using 5 mol % skeletal Ni catalyst at 20 °C and produced [Me(2)N-BH(2)](2) (2) and [Et(2)N-BH(2)](2)/Et(2)N═BH(2) (6), respectively. The related adduct iPr(2)NH·BH(3) (7) was also dehydrogenated to afford iPr(2)N═BH(2) (8) but with significant catalyst deactivation. Catalytic dehydrocoupling of MeNH(2)·BH(3) (9) was found to yield the cyclic triborazane [MeNH-BH(2)](3) (10) as the major product, whereas high molecular weight poly(methylaminoborane) [MeNH-BH(2)](n) (11) (M(w) = 78 000 Da, PDI = 1.52) was formed when stoichiometric quantities of Ni were used. Similar reactivity was also observed with NH(3)·BH(3) (12), which produced cyclic oligomers and insoluble polymers, [NH(2)-BH(2)](x) (14), under catalytic and stoichiometric Ni loadings, respectively. Catalyst recycling was hindered by gradual poisoning. A study of possible catalyst poisons suggested that BH(3) was the most likely surface poison, in line with previous work on colloidal Rh catalysts. Catalytic dehydrogenation of amine-borane adducts using skeletal Cu and Fe was also explored. Skeletal Cu was found to be a less active dehydrogenation catalyst for amine-borane adducts but also yielded poly(methylaminoborane) under stoichiometric conditions on reaction with MeNH(2)·BH(3) (9). Skeletal Fe was found to be completely inactive toward amine-borane dehydrogenation.