Titanocene and Zirconocene Complexes with Diaminoacetylenes: Formation of Unusual Metallacycles and Fulvene Complexes
Titanocene and Zirconocene Complexes with Diaminoacetylenes: Formation of Unusual Metallacycles and Fulvene Complexes
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DOI：
10.1021/om500121p
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发表时间：
2014-04-14
期刊：
影响因子：
2.8
通讯作者：
Tamm, Matthias
中科院分区：
文献类型：
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作者：
Arias, Oscar;Petrov, Alex R.;Tamm, Matthias
二吡啶乙炔（pipC Cpip, pip = NC5H10, 1a）与[Cp2Ti(eta(2)-btmsa)](2)或[Cp2Zr(eta(2)-btmsa)(py)] (4) （btmsa =双（三甲基硅基）乙炔，py =吡啶）反应生成金属环戊二烯[Cp2M(C(4)pip(4)] (3, M = Ti; 5, M = Zr)，在固态下表现出扭曲的五元金属环，具有罕见的半座构象。相比之下，空间要求更高的十甲基二茂钛（Cp*Ti-2）和-二茂锆（Cp*Zr-2）配合物片段只能容纳一个炔配体。因此，在镁的存在下，la与[Cp*2Ti(eta(2)-btmsa)](6)或与[Cp*2TiCl]反应分离得到钛环丙烯[Cp*2Ti(C(2)pip(2))](7)，而[Cp*Zr-2(C2X2)] (8a, X = pip; 8b, X = NC5H9-4-Me)]由[Cp*2ZrCl2]与镁在la、双（4-甲基哌替啶）乙炔（1b）和双（二乙胺）乙炔（1c）的存在下分别还原得到[Cp*2ZrCl2]， 8c, X = NEW。核磁共振研究表明，配合物8在溶液中与四甲基五氟烯二氨基异构体[Cp*(eta(6)-C5Me4CH2)Zr(CX=CHX)](9)处于平衡状态，这些异构体是由分子内C -氢键活化和氢从一个Cp*甲基转移到炔配体上形成的。通过变温核磁共振波谱和离散傅立叶变换实验得到了热力学和动力学参数。通过x射线衍射分析确定了3、5、7、8a、[8a中心点MgCl2](2)、8b和8c的分子结构。
The reaction of dipiperidinoacetylene (pipC Cpip, pip = NC5H10, 1a) with [Cp2Ti(eta(2)-btmsa)] (2) or with [Cp2Zr(eta(2)-btmsa)(py)] (4) (btmsa = bis(trimethylsilyl)acetylene, py = pyridine) afforded the metallacyclopentadienes [Cp2M(C(4)pip(4))] (3, M = Ti; 5, M = Zr), which in the solid state exhibit twisted five-membered metallacycles with an unusual half-chair conformation. In contrast, the sterically more demanding decamethyltitanocene (Cp*Ti-2) and -zirconocene (Cp*Zr-2) complex fragments can only accommodate one alkyne ligand. Thus, the titanacyclopropene [Cp*2Ti(C(2)pip(2))] (7) was isolated from the reaction of la with [Cp*2Ti(eta(2)-btmsa)] (6) or with [Cp*2TiCl] in the presence of magnesium, whereas the zirconacyclopropenes [Cp*Zr-2(C2X2)] (8a, X = pip; 8b, X = NC5H9-4-Me; 8c, X = NEW were prepared by the reduction of [Cp*2ZrCl2] with magnesium in the presence of la, bis(4-methylpiperidino)acetylene (1b), and bis(diethylamino)acetylene (1c), respectively. NMR studies showed that complexes 8 are in equilibrium with their tucked-in tetramethylpentafulvene-diaminovinyi isomers [Cp*(eta(6)-C5Me4CH2)Zr(CX=CHX)] (9) in solution, which are formed by intramolecular C H-bond activation and hydrogen transfer from one Cp* methyl group to the alkyne ligand. Thermodynamic and kinetic parameters were derived by variable-temperature NMR spectroscopy and DFT experiments. The molecular structures of 3, 5, 7, 8a, [8a center dot MgCl2](2), 8b, and 8c were established by X-ray diffraction analyses.