Understanding Precatalyst Activation and Speciation in Manganese-Catalyzed C-H Bond Functionalization Reactions.
Understanding Precatalyst Activation and Speciation in Manganese-Catalyzed C-H Bond Functionalization Reactions.
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DOI：
10.1021/acs.organomet.3c00004
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发表时间：
2023-07-24
期刊：
影响因子：
2.8
通讯作者：
Lynam, Jason M.
中科院分区：
文献类型：
--
作者：
Eastwood, Jonathan B.;Hammarback, L. Anders;Burden, Thomas J.;Clark, Ian P.;Towrie, Michael;Robinson, Alan;Fairlamb, Ian J. S.;Lynam, Jason M.
报道了Mn催化C-H键官能化反应中催化剂预活化后形成的物种的研究。时间分辨红外光谱表明，光诱导CO从预催化剂[Mn（C^N）（CO）4]中解离（C^N =环化的2-苯基吡啶（1a），环化的1，1-双（4-甲氧基苯基）甲亚胺（1b））在2-苯基吡啶（2a）或1，1-双（4-甲氧基苯基）甲亚胺（2b）导致溶剂络合物fac-[Mn（C^N）（CO）3（甲苯）]的初始形成。随后在纳秒时间尺度上的溶剂取代然后分别产生fac-[Mn（C^N）（CO）3（κ1-（N）-2a）]和fac-[Mn（C^N）（CO）3（κ1-（N）-2b）]。当在苯乙炔存在下进行实验时，fac-[Mn（C^N）（CO）3（甲苯）]的初始形成之后是竞争性取代反应，得到fac-[Mn（C^N）（CO）3（2）]和fac-[Mn（C^N）（CO）3（η2-PhC 2 H）]。反应混合物的命运取决于所用含氮底物的性质。在2-苯基吡啶的情况下，发生炔迁移插入Mn-C键，并且fac-[Mn（C^N）（CO）3（κ1-（N）-2a）]保持不变。相比之下，当使用2b时，η2结合的苯乙炔被2b取代发生在微秒的时间尺度上，并且fac-[Mn（C^N）（CO）3（κ1-（N）-2b）]是反应的唯一产物。用密度泛函理论计算表明，这种行为上的差异可能与2a和2b对锰的不同亲和力有关。因此，这项研究表明，物种形成后立即预催化剂活化是一个动力学控制的事件。反应混合物（溶剂）中最主要的物质最初与金属结合。随后的取代的金属结合的溶剂也动力学控制（在ns的时间尺度）之前，得到的产物的热力学分布。
An investigation into species formed following precatalyst activation in Mn-catalyzed C–H bond functionalization reactions is reported. Time-resolved infrared spectroscopy demonstrates that light-induced CO dissociation from precatalysts [Mn(C^N)(CO)4] (C^N = cyclometalated 2-phenylpyridine (1a), cyclometalated 1,1-bis(4-methoxyphenyl)methanimine (1b)) in a toluene solution of 2-phenylpyridine (2a) or 1,1-bis(4-methoxyphenyl)methanimine (2b) results in the initial formation of solvent complexes fac-[Mn(C^N)(CO)3(toluene)]. Subsequent solvent substitution on a nanosecond time scale then yields fac-[Mn(C^N)(CO)3(κ1-(N)-2a)] and fac-[Mn(C^N)(CO)3(κ1-(N)-2b)], respectively. When the experiments are performed in the presence of phenylacetylene, the initial formation of fac-[Mn(C^N)(CO)3(toluene)] is followed by a competitive substitution reaction to give fac-[Mn(C^N)(CO)3(2)] and fac-[Mn(C^N)(CO)3(η2-PhC2H)]. The fate of the reaction mixture depends on the nature of the nitrogen-containing substrate used. In the case of 2-phenylpyridine, migratory insertion of the alkyne into the Mn–C bond occurs, and fac-[Mn(C^N)(CO)3(κ1-(N)-2a)] remains unchanged. In contrast, when 2b is used, substitution of the η2-bound phenylacetylene by 2b occurs on a microsecond time scale, and fac-[Mn(C^N)(CO)3(κ1-(N)-2b)] is the sole product from the reaction. Calculations with density functional theory indicate that this difference in behavior may be correlated with the different affinities of 2a and 2b for the manganese. This study therefore demonstrates that speciation immediately following precatalyst activation is a kinetically controlled event. The most dominant species in the reaction mixture (the solvent) initially binds to the metal. The subsequent substitution of the metal-bound solvent is also kinetically controlled (on a ns time scale) prior to the thermodynamic distribution of products being obtained.
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影响因子：
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