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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Understanding the directed ortho lithiation of (R)-Ph2P(=NCO_2Me)NHCH(Me)Ph. NMR spectroscopic and computational study of the structure of the N-lithiated species
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Understanding the directed ortho lithiation of (R)-Ph2P(=NCO_2Me)NHCH(Me)Ph. NMR spectroscopic and computational study of the structure of the N-lithiated species

机译：了解（R）-Ph2P（= NCO_2Me）NHCH（Me）Ph的定向邻位锂化。 N锂化物种的结构的NMR光谱和计算研究

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A multinuclear magnetic resonance (~1H, ~7Li, ~(13)C, ~(15)N, ~(31)P) and DFT computational study at the M06-2X-(SMD,THF)/6-311+G(d,p)//B3LYP/6-31G(d) level of the structure of a N-lithiated phosphinimidic amide (R)-Ph_2P(vNCO_2Me)NHCH(Me)Ph 13 has been performed. In THF solution it exists as an equilibrium mixture of monomers and dimers. The monomers consist of a six-membered ring formed by coordination of the lithium atom with the deprotonated nitrogen and the oxygen atom of the carbonyl group. This coordination mode is in contrast to the standard N,N-chelation observed in N-lithiated N,N’-bis-(trimethylsilyl)phosphinimidic amides. The calculations showed that the metallacycle adopts a twist-boat conformation and that the lithium atom is in a tetrahedral environment involving O,N-chelation by the ligand and coordination to two/one THF molecules in the monomer/dimer. Dimerization takes place through O–Li bridges. For all species two series of isomers have been identified, which originated by restricted rotation of the methoxy group and ring inversion. The twist-boat conformational interconversion seems to be operating for explaining the pattern of signals observed in the ~7Li and ~(31)P NMR spectra. The structure found for the most stable dimer is analogous to the molecular structure reported for a related C_α-lithiated phosphazene 20. The structural study revealed that the chiral side-arm of the N-lithiated species is oriented to the outer face of the pro-S P-phenyl ring, which shows one orthoproton very close to the nitrogen atom of the carbamate moiety. In this conformation, proton abstraction by a base is highly favoured, in agreement with the experimental results.
机译：M06-2X-（SMD，THF）/ 6-311 + G的多核磁共振（〜1H，〜7Li，〜（13）C，〜（15）N，〜（31）P）和DFT计算研究已进行了N-锂化膦亚酰胺（R）-Ph_2P（vNCO_2Me）NHCH（Me）Ph 13的（d，p）// B3LYP / 6-31G（d）能级。在THF溶液中，它以单体和二聚体的平衡混合物形式存在。单体由锂原子与去质子化的氮和羰基的氧原子配位而形成的六元环组成。这种配位模式与在N-锂化的N，N'-双-（三甲基甲硅烷基）膦亚酰胺中观察到的标准N，N-螯合相反。计算表明，金属环具有扭转舟构象，并且锂原子处于四面体环境中，其中配体进行O，N螯合并与单体/二聚体中的两个/一个THF分子配位。二聚通过O-Li桥发生。对于所有物种，已经鉴定出两个系列的异构体，其起源于甲氧基的受限旋转和环反转。扭转舟构象互变似乎可以解释在〜7Li和〜（31）P NMR光谱中观察到的信号模式。发现最稳定的二聚体的结构类似于报道的相关C_α-锂化磷腈20的分子结构。该结构研究表明，N-锂化物种的手性侧臂面向前交联的外表面。 S P-苯环，显示一个非常接近氨基甲酸酯部分氮原子的原质子。在这种构象中，与实验结果相一致，高度支持通过碱提取质子。

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