Coordination-Induced Weakening of a C(sp3)–H Bond: Homolytic and Heterolytic Bond Strength of a CH–Ni Agostic Interaction
Coordination-Induced Weakening of a C(sp3)–H Bond: Homolytic and Heterolytic Bond Strength of a CH–Ni Agostic Interaction
复制标题
配位诱导的 C(sp3)–H 键弱化：CH–Ni 不自由相互作用的均解和杂解键强度
DOI：
10.1021/jacs.2c05667
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发表时间：
2022
影响因子：
15
通讯作者：
Prokopchuk, Demyan E.
中科院分区：
文献类型：
--
作者：
Lin, Lirong;Spasyuk, Denis M.;Lalancette, Roger A.;Prokopchuk, Demyan E.
C(sp3) -H键断裂形成新的金属-烷基键是配位化学和催化的基本步骤。然而，当这部分与过渡金属相互作用时，C-H键减弱的程度尚不清楚，量化这一现象可以为设计更有效的C-H功能化催化剂提供见解。我们提出了一个具有坚固金刚烷基报告配体的镍配合物，可以测量C(sp3) -H相互作用的C -H酸度（pKa）和键解离自由能（BDFE），显示配位后pKaby降低了几十个数量级，BDFE降低了约30千卡/摩尔。提供了所有分子的x射线晶体学数据，包括一个扭曲的方形平面NiII金属基和“双agostic”NiII（κ2-CH2）配合物。
The scission of a C(sp3)–H bond to form a new metal–alkyl bond is a fundamental step in coordination chemistry and catalysis. However, the extent of C–H bond weakening when this moiety interacts with a transition metal is poorly understood and quantifying this phenomenon could provide insights into designing more efficient C–H functionalization catalysts. We present a nickel complex with a robust adamantyl reporter ligand that enables the measurement of C–H acidity (pKa) and bond dissociation free energy (BDFE) for a C(sp3)–H agostic interaction, showing a decrease in pKaby dozens of orders of magnitude and BDFE decrease of about 30 kcal/mol upon coordination. X-ray crystallographic data is provided for all molecules, including a distorted square planar NiIIImetalloradical and “doubly agostic” NiII(κ2-CH2) complex.