Ruthenium complexes with novel tridentate N,P,N ligands containing a phosphonite bridge between two chiral oxazolines. Catalytic activity in cyclopropanation of olefins and transfer hydrogenation of acetophenone
Ruthenium complexes with novel tridentate N,P,N ligands containing a phosphonite bridge between two chiral oxazolines. Catalytic activity in cyclopropanation of olefins and transfer hydrogenation of acetophenone
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DOI：
10.1021/om991034m
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发表时间：
2000-07-10
期刊：
影响因子：
2.8
通讯作者：
Rettig, SJ
中科院分区：
文献类型：
--
作者：
Braunstein, P;Naud, F;Rettig, SJ
我们比较了新型手性配体 (S,S)-双[1-(4-异丙基-4,5-二氢恶唑-2-基)-1-甲基乙基]苯基亚膦酸酯 (V)（缩写为 NOPONiPr，称为双（恶唑啉基）苯基亚膦酸酯）与 NOPONMe2 (TV) 对 Ru(II) 的配位行为，尽管 IV 和 V 之间的相似性导致预期它们会以类似地，观察到相当大的差异。 [RuCl2(eta(6)-p-伞花烃)](2) 与 IV 的反应得到五配位络合物 [RuCl2(NOPONMe2)] 1，而手性配体 V 则生成双核氯桥络合物 [Ru(mu-Cl)Cl(NOPONiPr)](2) (3)。 1和3的晶体结构已通过X射线衍射确定，1中NOPONMe2配体的mer排列是由于四个甲基的存在而导致的，如果采用面式几何结构，其中两个甲基将指向彼此并导致空间冲突。在EHT水平上对1的初步理论计算表明，乙烯与RuCl2P平面平行的配位会导致稳定的情况，并且由于空间原因，乙烯不与平行或垂直于RuCl2P平面的金属配位。研究发现，CO 与 1 的配位是可逆的，而较大的配体不会与 Ru 配位，配合物 3 是完全表征的配合物的罕见例子，其中三齿手性双（恶唑啉）型配体以非基体方式配位。它在催化反应中进行了评估，例如苯乙烯与重氮乙酸乙酯的不对称环丙烷化和苯乙酮在丙-2-醇中的转移氢化。
We compare the coordination behavior of the new chiral ligand (S,S)-bis[1-(4-isopropyl-4,5-dihydrooxazol-2-yl)-1-methylethyl] phenylphosphonite (V), abreviated NOPONiPr and referred to as bis(oxazolinyl) phenylphosphonite, toward Ru(II) with that of NOPONMe2 (TV), Although the similarity between IV and V led to the expectation that they would coordinate in a similar manner, considerable differences were observed. Whereas reaction of [RuCl2(eta(6)-p-cymene)](2) with IV afforded the pentacoordinated complex [RuCl2(NOPONMe2)] 1, the chiral ligand V led instead to the dinuclear, chloride-bridged complex [Ru(mu-Cl)Cl(NOPONiPr)](2) (3). The crystal structures of 1 and 3 have been determined by X-ray diffraction, The mer arrangement of the NOPONMe2 ligand in 1 results from the presence of the four methyl groups, two of which would point toward each other and lead to a steric clash if a fac geometry were adopted. Preliminary theoretical calculations on 1 at the EHT level indicated that coordination of ethylene parallel to the RuCl2P plane would result in a stable situation and it is for steric reasons that ethylene does not coordinate to the metal, either parallel or perpendicular to the RuCl2P plane. Coordination of CO to 1 was found to be reversible, whereas bulkier ligands do not coordinate to Ru, Complex 3 is a rare example of a fully characterized complex in which a tridentate chiral bis(oxazoline)-type ligand coordinates in a non-mer fashion. It was evaluated in catalytic reactions such as asymmetric cyclopropanation of styrene with ethyl diazoacetate and transfer hydrogenation of acetophenone in propan-2-ol.