Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, 52056 Aachen (Germany), Fax: (+49) 241-80-92644.
Chemistry. 2013 Sep 27;19(40):13437-44. doi: 10.1002/chem.201301732. Epub 2013 Aug 14.
The rare-earth-metal-hydride complexes [{(1,7-Me2TACD)LnH}4] (Ln=La 1 a, Y 1 b; (1,7-Me2TACD)H2 =1,7-dimethyl-1,4,7,10-tetraazacyclododecane, 1,7-Me2[12]aneN4) were synthesized by hydrogenolysis of [{(1,7-Me2TACD)Ln(η(3)-C3H5)}2] with 1 bar H2. The tetrameric structures were confirmed by (1)H NMR spectroscopy and single-crystal X-ray diffraction of compound 1 a. Both complexes catalyze the dehydrogenation of secondary amine-borane Me2NH·BH3 to afford the cyclic dimer (Me2NBH2)2 and (Me2N)2BH under mild conditions. Whilst the complete conversion of Me2NH·BH3 was observed within 2 h with lanthanum-hydride 1 a, the yttrium homologue 1 b required 48 h to reach 95% conversion. Further reactions of compound 1 a with Me2NH·BH3 in various stoichiometric ratios gave a series of intermediate products, {(1,7-Me2TACD)LaH}42 (2 a), [(1,7-Me2TACDH)La(Me2NBH3)2] (3 a), [(1,7-Me2TACD)(Me2NBH2)La(Me2NBH3)] (4 a), and [(1,7-Me2TACD)(Me2NBH2)2La(Me2NBH3)] (5 a). Complexes 2 a, 3 a, and 5 a were isolated and characterized by multinuclear NMR spectroscopy and single-crystal X-ray diffraction studies. These intermediates revealed the activation and coordination modes of "Me2NH·BH3 " fragments that were trapped within the coordination sphere of a rare-earth-metal center.
[{(1,7-Me2TACD)LnH}4]（Ln=La 1a，Y 1b；(1,7-Me2TACD)H2=1,7-二甲基-1,4,7,10-四氮杂环十二烷，1,7-Me2[12]aneN4）是通过 1 巴 H2 氢化[{(1,7-Me2TACD)Ln(η(3)-C3H5)}2]得到的稀土金属氢化物配合物。通过 1a 的（1）H NMR 光谱和单晶 X 射线衍射证实了四聚体结构。这两种配合物都能在温和条件下催化仲胺-硼烷 Me2NH·BH3 的脱氢反应，生成环状二聚体(Me2NBH2)2和(Me2N)2BH。尽管镧氢化物 1a 能在 2 小时内完全转化 Me2NH·BH3，但相应的钇配合物 1b 需要 48 小时才能达到 95%的转化率。进一步反应的化合物 1a 与 Me2NH·BH3 的各种化学计量比，得到一系列中间产物，{(1,7-Me2TACD)LaH}42（2a），[(1,7-Me2TACDH)La(Me2NBH3)2]（3a），[(1,7-Me2TACD)(Me2NBH2)La(Me2NBH3)]（4a）和[(1,7-Me2TACD)(Me2NBH2)2La(Me2NBH3)]（5a）。配合物 2a、3a 和 5a 被分离并通过多核 NMR 光谱和单晶 X 射线衍射研究进行了表征。这些中间体揭示了“Me2NH·BH3”片段的活化和配位模式，这些片段被捕获在稀土金属中心的配位球中。
