Preparation of Imidazolin-2-iminato Molybdenum and Tungsten Benzylidyne Complexes: A New Pathway to Highly Active Alkyne Metathesis Catalysts
Preparation of Imidazolin-2-iminato Molybdenum and Tungsten Benzylidyne Complexes: A New Pathway to Highly Active Alkyne Metathesis Catalysts
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DOI：
10.1002/chem.201000597
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发表时间：
2010-01-01
影响因子：
4.3
通讯作者：
Tamm, Matthias
中科院分区：
文献类型：
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作者：
Haberlag, Birte;Wu, Xian;Tamm, Matthias
[PhC MBr 3-（dme）]的反应（dme= 1，2-二甲氧基乙烷）与六氟叔丁氧化合物LiX或KX [X = OC（CF_3）（2）Me]反应，得到苯甲基配合物[PhCMX_3-（dme）]（2a：M=W，2b：M=Mo），其进一步与由1，3-二叔丁基咪唑啉-2-亚胺（Im（tBu）NH）与MeLi生成的锂试剂Li（Im（tBu）N）反应，以形成咪唑啉-2-亚氨基配合物[PhCMX 2-（Im（tBu）N）]（3a：M=W，3b：M=Mo）。通过用过量的3-己炔处理3b获得亚丙基络合物[EtC MoX 2-（Nlm（tBu））]（4）。配合物3a和3b能够在室温下有效地催化各种3-戊炔基苄基醚5和苯甲酸酯7的炔交叉复分解，以提供2-丁炔和相应的二醚6和二酯8。钨配合物3a被证明是一种上级的炔复分解闭环催化剂，并分别由1，3-二（3-戊炔氧基甲基）苯（9）和邻苯二甲酸二（3-戊炔基）酯（11）高产率地合成了[10]环番10和12。化合物2a、2b、3a、3b、4和12的分子结构通过单晶X-射线衍射测定。以2-丁炔的炔复分解反应为模型反应，对咪唑啉-2-亚氨基钨和钼配合物3a和3b的催化体系进行了密度泛函理论计算，结果表明钨体系具有较低的活化能垒。
The reaction of [PhC MBr3-(dme)] (dme=1,2-dimethoxyethane) with the hexafluoro-tert-butoxides LiX or KX [X = OC(CF3)(2)Me] afforded the benzylidyne complexes [PhC MX3-(dme)] (2a: M=W, 2b: M=Mo), which further reacted with the lithium reagent Li(Im(tBu)N) generated with MeLi from 1,3-di-tert-butylimidazolin-2-imine (Im(tBu)NH), to form the imidazolin-2-iminato complexes [PhC MX2-(Im(tBu)N)] (3a: M=W, 3b: M=Mo). The propylidyne complex [EtC MoX2-(Nlm(tBu))] (4) was obtained by treatment of 3b with an excess of 3-hexyne. Complexes 3a and 3b are able to efficiently catalyse alkyne cross metathesis of various 3-pentynyl benzyl ethers 5 and benzoic esters 7 at room temperature, to afford 2-butyne and the corresponding diethers 6 and diesters 8. The tungsten complex 3a proved to be a superior catalyst for ring-closing alkyne metathesis, and the [10]cyclophanes 10 and 12 were synthesised in high yield from 1,3-bis(3-pentynyloxymethyl)ben- zene (9) and bis(3-pentynyl) phthalate (11), respectively. The molecular structures of compounds 2a, 2b, 3a, 3b, 4, and 12 were determined by single-crystal X-ray diffraction. DFT calculations have been carried out for catalyst systems based on the imidazolin-2-iminato tungsten and molybdenum complexes 3a and 3b by choosing the alkyne metathesis of 2-butyne as the model reaction; the studies revealed a lower activation barrier for the tungsten system.