Reactions of Low-Valent Titanocene(II) Fragments with trans-4,4′-Azobispyridine (RN═NR, R = C5H4N): Formation of Tetranuclear Molecular Squares by trans−cis Isomerization
Reactions of Low-Valent Titanocene(II) Fragments with trans-4,4′-Azobispyridine (RN═NR, R = C5H4N): Formation of Tetranuclear Molecular Squares by trans−cis Isomerization
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低价二茂钛 (II) 片段与反式 4,4β-偶氮二吡啶 (RNâNR, R = C5H4N) 的反应：通过反式异构化形成四核分子方形
DOI：
10.1021/om801123k
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发表时间：
2009
期刊：
影响因子：
2.8
通讯作者：
R. Beckhaus
中科院分区：
文献类型：
--
作者：
O. Theilmann;W. Saak;D. Haase;R. Beckhaus
低价茂钛化合物[Cp* 2 Ti（η2-C2（TMS）2）]（2）和[tBuCp 2 Ti（η2-C2（TMS）2）]（3）与反式-4，4 ′-偶氮双吡啶（8）反应，得到新型超分子方[（Cp* 2 Ti）4（μ2-N，N′;η2-N，N′-C10 H8 N4）2]（10）和[（tBuCp 2 Ti）4（μ2-N，N′;η2-N，N′-C10 H8 N4）2]（11）.这些配合物由四个β-二茂钛角单元和两个偶氮配体组成8。在这个自组装过程中，偶氮配体经历了构象重排。二茂钛部分嵌入两个不同的N-供体环境，由吡啶环和偶氮官能团提供8。四核化合物10和11的单晶X射线分析揭示了这些分子多边形的结构特征。在10和11中检测到完全的顺式构型的偶氮吡啶单元。配位和自由配体的键长和键角的比较显示了低价钛络合物10和11中桥连配体的还原状态。这样，纳佐−纳佐距离从1.251（2）in 8分别延长到av 1.405（3）（10）和1.434（3）（11）。对这些新化合物的合成和性质进行了讨论。从[Cp_2Ti（η_2-C_2（TMS）_2）]（1）与8的反应中分离出1，2-双（4-吡啶基）肼（13），并作为后续产物进行了充分表征。
The reactions of the low-valent titanocene sources [Cp*2Ti(η2-C2(TMS)2)] (2) and [tBuCp2Ti(η2-C2(TMS)2)] (3) withtrans-4,4′-azobispyridine (8) leads to novel supramolecular squares [(Cp*2Ti)4(μ2-N,N′;η2-N,N′-C10H8N4)2] (10) and [(tBuCp2Ti)4(μ2-N,N′;η2-N,N′-C10H8N4)2] (11). These complexes consist of four bent-titanocene corner units and two azo ligands8. Within this self-assembly process the azo ligands experience a conformational rearrangement fromtranstocis. The titanocene moieties are embedded with two different N-donor environments, provided by the pyridyl rings and the azo functionality of8. Single-crystal X-ray analyses of the tetranuclear compounds10and11revealed the structural features of these molecular polygons. Exclusivelycis-configurated azopyridine units are detected in10and11. Comparison of bond lengths and angles in coordinated and free ligands shows a reduced state of the bridging ligands in the low-valent titanium complexes10and11. In such a way, the Nazo−Nazodistances are elongated from 1.251(2) Å in8to av 1.405(3) Å (10) and 1.434(3) Å (11), respectively. The syntheses and attributes of these novel compounds are discussed. From the reaction of [Cp2Ti(η2-C2(TMS)2)] (1) with8, 1,2-bis(4-pyridyl)hydrazine (13) was isolated and fully characterized as a subsequent product.