C (sp3) –H Oxidative Addition at Tantalocene Hydrides
C (sp3) –H Oxidative Addition at Tantalocene Hydrides
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C (sp3) – H 钽茂氢化物的氧化加成
DOI：
10.1021/acs.organomet.2c00672
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发表时间：
2023
期刊：
影响因子：
2.8
通讯作者：
Neufeldt, Sharon R.
中科院分区：
文献类型：
--
作者：
Rehbein, Steven M.;Kania, Matthew J.;Neufeldt, Sharon R.
虽然后过渡金属通过氧化加成活化烷烃C-H键是众所周知的，但这种机制步骤对于前过渡金属是非典型的。相反，在早期过渡金属处的分子间C（sp3）-H活化的先前实例倾向于通过σ-键复分解或1，2-加成机制进行。最近的理论工作表明，二茂钽可能能够通过氧化加成激活脂肪族C-H键。在此，我们证明，单烷基取代的tantalocenesRCp 2 TaH 3进行H/D交换的烷基取代基“R”在C6 D 6的存在下，表明分子内C（sp3）-H活化发生。此外，Cp 2 TaH 3被发现催化H2和辛烷-d18和甲基环己烷-d14之间的H/D交换，这表明分子间C（sp3）-H活化步骤的参与。密度泛函理论计算支持C（sp3）-H氧化加成在瞬态Ta（III），一个机械步骤，以前没有看到在钽的烷烃分子间活化。
Although late transition metals are well-known to activate alkane C–H bonds through oxidative addition, this mechanistic step is atypical for early transition metals. Instead, prior examples of intermolecular C(sp3)–H activation at early transition metals tend to proceed through σ-bond metathesis or 1,2-addition mechanisms. Recent theoretical work suggested that tantalocenes may be capable of activating aliphatic C–H bonds by oxidative addition. Herein, we demonstrate that monoalkyl-substituted tantalocenesRCp2TaH3undergo H/D exchange on the alkyl substituent “R” in the presence of C6D6, indicating that intramolecular C(sp3)–H activation takes place. Moreover, Cp2TaH3was found to catalyze H/D exchange between H2and octane-d18and methylcyclohexane-d14, an indication of the involvement of an intermolecular C(sp3)–H activation step. Density functional theory calculations support C(sp3)–H oxidative addition at transient Ta(III), a mechanistic step that has not been previously seen for intermolecular activation of alkanes at tantalum.