The exceptionally π-basic metal fragments {MoTp(NO)(DMAP)} and {WTp(NO)(PMe₃)} (Tp = tris(pyrazolyl)borate; DMAP = 4-(N,N-dimethylamino)pyridine) form thermally stable η²-coordinated complexes with a variety of electron-deficient arenes. The tolerance of substituted arenes with fluorine-containing electron withdrawing groups (EWG; −F, −CF₃, −SF₅) is examined for both the molybdenum and tungsten systems. When the EWG contains a π bond (nitriles, aldehydes, ketones, ester), η² coordination occurs predominantly on the nonaromatic functional group. However, complexation of the tungsten complex with trimethyl orthobenzoate (PhC(OMe)₃) followed by hydrolysis allows access to an η²-coordinated arene with an ester substituent. In general, the tungsten system tolerates sulfur-based withdrawing groups well (e.g., PhSO₂Ph, MeSO₂Ph), and the integration of multiple electron-withdrawing groups on a benzene ring further enhances the π-back-bonding interaction between the metal and aromatic ligand. While the molybdenum system did not form stable η²-arene complexes with the sulfones or ortho esters, it was capable of forming rare examples of stable η²-coordinated arene complexes with a range of fluorinated benzenes (e.g., fluorobenzene, difluorobenzenes). In contrast to what has been observed for the tungsten system, these complexes formed without interference of C–H or C–F insertion.

中文翻译：

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η ²缺电子芳烃的协调与组6脱芳代理

特殊的π碱性金属片段{MoTp（NO）（DMAP）}和{WTp（NO）（PMe ₃）}（Tp =三（吡唑基）硼酸酯； DMAP = 4-（N，N-二甲基氨基）吡啶）形式热稳定的η ²配位的配合物与各种缺电子芳烃的。对于钼和钨系统，均检查了具有含氟吸电子基团（EWG; -F，-CF ₃，-SF ₅）的取代芳烃的耐受性。当EWG包含π键（腈，醛，酮，酯），η ²配位主要发生在非芳族官能团。但是，钨配合物与原苯甲酸三甲酯（PhC（OMe）₃），接着水解允许访问一个η ²与酯取代基配位的芳烃。通常，钨系统很好地耐受了硫基的吸电子基团（例如，PhSO ₂ Ph，MeSO ₂ Ph），并且多个电子吸电子基团在苯环上的集成进一步增强了金属之间的π背键相互作用和芳香配体。虽然钼系统没有形成稳定的η ^2个-arene络合物与砜或原酸酯，这是能够形成稳定的η的罕见例子的²-配位芳烃配合物与一定范围的氟化苯（例如氟苯，二氟苯）。与观察到的钨体系相反，这些络合物的形成不受CH或CF插入的干扰。