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Dinitrogen Activation and Hydrogenation by C5Me4SiMe3-Ligated Di- and Trinuclear Chromium Hydride Complexes
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2020-04-17 , DOI: 10.1021/jacs.0c02939
Takanori Shima 1, 2 , Jimin Yang 3 , Gen Luo 3 , Yi Luo 3 , Zhaomin Hou 1, 2, 3
Affiliation  

Activation of dinitrogen (N2) by well-defined metal hydrides is of much interest and importance, but studies in this area have remained limited to date. We report here N2 activation and hydrogenation by C5Me4SiMe3-ligated di- and trinuclear chromium polyhydride com-plexes. Hydrogenolysis of [Cp'Cr(μ-Me)2CrCp'] (Cp' = C5Me4SiMe3) (1) with H2 in a dilute hexane solution under N2-free conditions affords the dichromium dihydride complex [Cp'Cr(μ-H)2CrCp'] (2), while hydrogenolysis of 1 in a concentrated solution or without solvent provides the trinuclear chromium tetrahydride complex [(Cp'Cr)3(μ3-H)(μ-H)3] (3). When the reaction is carried out in the presence of N2 in a dilute hexane solution, a tetranuclear diimide/dihydride complex [(Cp'Cr)4(μ3-NH)2(μ3-H)2] (4) is formed via N-N bond cleav-age and N-H bond formation. The reaction of 2 with N2 at room temperature gives a tetranuclear imide/nitride/dihydride complex [(Cp'Cr)3(C5Me3(CH2)SiMe3)Cr(μ3-NH)(μ3-N)(μ-H)2] (5) via N2 cleavage and hydrogenation and C-H bond activation of a Cp-methyl group. At -30 °C, the reaction of 2 with N2 affords a dinitride intermediate [(Cp'Cr)4(μ3-N)2(μ3-H)2] (6), which is quantitatively trans-formed to 5 at room temperature. Complex 5 reversibly converts to a stereoisomer 5'. The hydrogenation of a mixture of 5 and 5' with H2 affords 4. The reaction of 3 with N2 proceeds at 100 °C to afford [(Cp'Cr)3(μ3-NH)2] (7). This transformation is also investigated by the DFT calculations. Both experimental and computational studies suggest that N2 incorporation into the chromium hydride cluster is in-volved in the rate-determining step. This work represents the first example of N2 cleavage and hydrogenation by well-defined chromium hydride complexes.

中文翻译:

C5Me4SiMe3-连接的二核和三核氢化铬配合物的二氮活化和氢化

明确定义的金属氢化物对二氮 (N2) 的活化引起了极大的兴趣和重要性,但迄今为止,该领域的研究仍然有限。我们在这里报告了 C5Me4SiMe3 连接的双核和三核多氢化铬络合物的 N2 活化和氢化。[Cp'Cr(μ-Me)2CrCp'] (Cp' = C5Me4SiMe3) (1) 在稀己烷溶液中在无 N2 条件下用 H2 氢解得到二氢化二铬配合物 [Cp'Cr(μ-H)2CrCp '] (2),而 1 在浓溶液或无溶剂中的氢解提供三核四氢化铬络合物 [(Cp'Cr)3(μ3-H)(μ-H)3] (3)。当反应在 N2 存在下在稀己烷溶液中进行时,通过 NN 形成四核二亚胺/二氢化物复合物 [(Cp'Cr)4(μ3-NH)2(μ3-H)2] (4)键断裂和 NH 键形成。2与N2在室温下反应得到四核酰亚胺/氮化物/二氢化物复合物[(Cp'Cr)3(C5Me3(CH2)SiMe3)Cr(μ3-NH)(μ3-N)(μ-H)2] (5) 通过 N2 裂解和氢化以及 Cp-甲基的 CH 键活化。在 -30 °C 下,2 与 N2 反应生成二氮化物中间体 [(Cp'Cr)4(μ3-N)2(μ3-H)2] (6),其在室温下定量转化为 5温度。复合物 5 可逆地转化为立体异构体 5'。5 和 5' 的混合物与 H2 氢化得到 4。3 与 N2 的反应在 100 °C 下进行,得到 [(Cp'Cr)3(μ3-NH)2] (7)。DFT 计算也研究了这种转换。实验和计算研究都表明 N2 掺入到氢化铬簇中参与了速率决定步骤。
更新日期:2020-04-17
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