Photochemistry of Cp'Mn(CO) 2 (NHC) (Cp' = ? 5 -C 5 H 4 Me) Species: Synthesis, Time-Resolved IR Spectroscopy, and DFT Calculations
Photochemistry of Cp'Mn(CO) 2 (NHC) (Cp' = ? 5 -C 5 H 4 Me) Species: Synthesis, Time-Resolved IR Spectroscopy, and DFT Calculations
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CpMn(CO) 2 (NHC) (Cp = ? 5 -C 5 H 4 Me) 物种的光化学：合成、时间分辨红外光谱和 DFT 计算
DOI：
10.1021/om300209a
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发表时间：
2012
期刊：
影响因子：
2.8
通讯作者：
Batool M
中科院分区：
文献类型：
--
作者：
Batool M
Cp ' mn (CO)3（Cp ' = η - 5- c5h4me）在游离n -杂环化合物ie2me2、IiPr2Me2、IMes和IPr存在下的紫外照射可得到NHC二羰基配合物Cp ' mn (CO)2(NHC)（1-4）。在烷烃溶液中，时间分辨红外光谱显示，1- 4光解CO生成Cp 'Mn (CO)(NHC) (1-CO,2-CO,3-CO,4-CO)，与CO反应表现出与溶剂无关的二阶速率常数（kCO）。这些观察结果与1- coto4 - co通过与NHCs的分子内原子相互作用而不是烷烃分子间配位稳定一致。密度泛函理论计算为这一假设提供了支持，并确定了从δ-agostic （1-CO,2-CO）到ε-agostic （3-CO）到ϕ-agostic （4-CO）的一系列agostic结构。分子中原子的方法被用来表征这些物质，以及在CpMn(CO)（PPh3）类似物（5-CO）中看到的γ-agostic相互作用，并表明这些物质主要由agostic环临界点处的电子密度大小来区分。
UV irradiation of Cp′Mn(CO)3(Cp′ = η5-C5H4Me) in the presence of the free N-heterocyclic carbenes IEt2Me2, IiPr2Me2, IMes, and IPr affords the NHC dicarbonyl complexes Cp′Mn(CO)2(NHC) (1–4). Time-resolved infrared spectroscopy in alkane solution reveals that1–4photodissociate CO to generate Cp′Mn(CO)(NHC) (1-CO,2-CO,3-CO,4-CO), which exhibit solvent-independent second-order rate constants (kCO) for reaction with CO. These observations are consistent with1-COto4-CObeing stabilized by intramolecular agostic interactions with the NHCs rather than intermolecular alkane coordination. Density functional theory calculations provide support for this hypothesis and locate a series of agostic structures varying from δ-agostic (1-CO,2-CO), to ε-agostic (3-CO), to ϕ-agostic (4-CO). The atoms-in-molecules approach is used to characterize these species, along with the γ-agostic interaction seen in the CpMn(CO)(PPh3) analogue (5-CO), and shows that these species are distinguished primarily by the magnitude of the electron density at the agostic ring critical point.