Dinitrogen functionalization with terminal alkynes, amines, and hydrazines promoted by [(η5-C5Me4H)2Zr]2(μ2,η2 η2-N2):: Observation of side-on and end-on diazenido complexes in the reduction of N2 to hydrazine
Dinitrogen functionalization with terminal alkynes, amines, and hydrazines promoted by [(η5-C5Me4H)2Zr]2(μ2,η2 η2-N2):: Observation of side-on and end-on diazenido complexes in the reduction of N2 to hydrazine
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DOI：
10.1021/ja050387b
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发表时间：
2005-06-01
影响因子：
15
通讯作者：
Chirik, PJ
中科院分区：
文献类型：
--
作者：
Bernskoetter, WH;Pool, JA;Chirik, PJ
在侧合二氮配合物[(eta(5)- c5me4h)(2)Zr](2-)(mu（2), eta(2), eta(2)- N-2)）中，N-2配体的功能化是通过添加末端炔得到乙酰基锆新二氮基配合物[(eta(5)- c5me4h)(2)Zr(C CR)](2)(mu(2), eta(2), eta(2)- n2h2)（R = Bu-n, Bu-t, Ph）完成的。通过x射线衍射表征[(eta(5)- c5me4h)(2)Zr(C CCMe3)](2)(mu（2), eta(2), eta(2)-N2H2)）在固体状态下发现了一个侧面结合的重氮基配体，而H-1和N-15 NMR研究发现了溶液中[N2H2]（2-）配体在eta(1), eta(1)和eta(2)之间的快速相互转化，eta(2)的hapticity。烷基、卤化物和三氧化锆二茂二氮基配合物[(eta(5)- c5me4h)(2)ZrX](2)(mu(2), eta(1),eta（1) -N2H2) (X = Cl， I, OTf, CH2Ph, CH2SiMe3)）的合成，使[N2H2]（2-）片段在固态和溶液中都具有eta(1),eta(1)配位，表明在某些情况下，具有空间要求的配体可以克服电子偏好的侧对键模式。与[(eta(5)-C5Me4H)(2)ZrH](2)(mu(2),eta（2),eta(2)-N2H2）不同，乙酰基和烷基锆新统重氮配合物在115℃的温度下具有热稳定性，抵抗a-迁移和N2裂解。[(eta(5)-C5Me4H)(2)Zr](2)(mu(2), eta（2),eta(2)-N-2）也通过添加质子供体实现了二氮功能化。弱酸如水和乙醇分别生成肼和（eta(5)-C5Me4H）(2)Zr(OH)(2)和（eta(5)-C5Me4H）(2)Zr(OEt)(2)。[(eta(5)-C5Me4H)(2)Zr](2)(mu(2),eta（2), eta(2)-N-2）用HNMe2或H2NNMe2提供的酰胺或肼基锆新二氮基配合物与乙醇质子化后最终生成肼。这些结果与先前的观察结果[(eta(5)-C5Me5)(2)Zr(eta(1)-N-2)](2)(mu(2),eta（1),eta(1)-N-2）形成对比，其中在弱酸处理后观察到游离二氮的损失。这些研究强调了环戊二烯基取代基在涉及配位二氮的转化中的重要性。
Functionalization of the N-2 ligand in the side-on bound dinitrogen complex, [(eta(5)-C5Me4H)(2)Zr](2-)(mu(2), eta(2), eta(2) -N-2), has been accomplished by addition of terminal alkynes to furnish acetylide zirconocene diazenido complexes, [(eta(5)-C5Me4H)(2)Zr(C CR)](2)(mu(2), eta(2), eta(2)-N2H2) (R = Bu-n, Bu-t, Ph). Characterization of [(eta(5)-C5Me4H)(2)Zr(C CCMe3)](2)(mu(2), eta(2), eta(2)-N2H2) by X-ray diffraction revealed a side-on bound diazenido ligand in the solid state, while variable-temperature H-1 and N-15 NMR studies established rapid interconversion between eta(1), eta(1) and eta(2), eta(2) hapticity of the [N2H2](2-) ligand in solution. Synthesis of alkyl, halide, and triflato zirconocene diazenido complexes, [(eta(5)-C5Me4H)(2)ZrX](2)(mu(2), eta(1), eta(1)-N2H2) (X = Cl, I, OTf, CH2Ph, CH2SiMe3), afforded eta(1),eta(1) coordination of the [N2H2](2-) fragment both in the solid state and in solution, demonstrating that sterically demanding, in some cases pi-donating, ligands can overcome the electronically preferred side-on bonding mode. Unlike [(eta(5)-C5Me4H)(2)ZrH](2)(mu(2),eta(2),eta(2)-N2H2), the acetylide and alkyl zirconocene diazeniclo complexes are thermally robust, resisting a-migration and N2 cleavage up to temperatures of 115 degrees C. Dinitrogen functionalization with [(eta(5)-C5Me4H)(2)Zr](2)(mu(2), eta(2),eta(2)-N-2) was also accomplished by addition of proton donors. Weak Bronsted acids such as water and ethanol yield hydrazine and (eta(5)-C5Me4H)(2)Zr(OH)(2) and (eta(5)-C5Me4H)(2)Zr(OEt)(2), respectively. Treatment of [(eta(5)-C5Me4H)(2)Zr](2)(mu(2),eta(2), eta(2)-N-2) with HNMe2 or H2NNMe2 furnished amido or hydrazido zirconocene diazenido complexes that ultimately produce hydrazine upon protonation with ethanol. These results contrast previous observations with [(eta(5)-C5Me5)(2)Zr(eta(1)-N-2)](2)(mu(2),eta(1),eta(1)-N-2) where loss of free dinitrogen is observed upon treatment with weak acids. These studies highlight the importance of cyclopentadienyl substituents on transformations involving coordinated dinitrogen.