In this article, we describe a combined experimental and theoretical mechanistic investigation of the C(sp²)–F bond formation from neutral and cationic high-valent organobismuth(V) fluorides, featuring a dianionic bis-aryl sulfoximine ligand. An exhaustive assessment of the substitution pattern in the ligand, the sulfoximine, and the reactive aryl on neutral triarylbismuth(V) difluorides revealed that formation of dimeric structures in solution promotes facile Ar–F bond formation. Noteworthy, theoretical modeling of reductive elimination from neutral bismuth(V) difluorides agrees with the experimentally determined kinetic and thermodynamic parameters. Moreover, the addition of external fluoride sources leads to inactive octahedral anionic Bi(V) trifluoride salts, which decelerate reductive elimination. On the other hand, a parallel analysis for cationic bismuthonium fluorides revealed the crucial role of tetrafluoroborate anion as fluoride source. Both experimental and theoretical analyses conclude that C–F bond formation occurs through a low-energy five-membered transition-state pathway, where the F anion is delivered to a C(sp²) center, from a BF₄ anion, reminiscent of the Balz–Schiemann reaction. The knowledge gathered throughout the investigation permitted a rational assessment of the key parameters of several ligands, identifying the simple sulfone-based ligand family as an improved system for the stoichiometric and catalytic fluorination of arylboronic acid derivatives.

中文翻译：

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Bi(V)氟化物形成芳基-F键的机理


在本文中，我们描述了中性和阳离子高价有机铋(V)氟化物形成C(sp ² )–F键的联合实验和理论机理研究，其特征是双阴离子双芳基亚磺酰亚胺配体。对配体、亚磺酰亚胺和中性二氟化三芳基铋(V)上的反应性芳基的取代模式的详尽评估表明，溶液中二聚结构的形成促进了Ar-F键的容易形成。值得注意的是，中性二氟化铋（V）还原消除的理论模型与实验确定的动力学和热力学参数一致。此外，添加外部氟化物源会产生无活性的八面体阴离子三氟化铋盐，从而减缓还原消除。另一方面，对阳离子氟化铋的平行分析揭示了四氟硼酸根阴离子作为氟化物源的关键作用。实验和理论分析都得出结论，C-F 键的形成是通过低能五元过渡态途径发生的，其中 F 阴离子从 BF ₄阴离子传递到 C(sp ² ) 中心，让人想起巴尔兹-希曼反应。在整个研究过程中收集的知识可以对几种配体的关键参数进行合理评估，确定简单的基于砜的配体家族作为芳基硼酸衍生物化学计量和催化氟化的改进系统。