Triarylsilanolates are privileged ancillary ligands for molybdenum alkylidyne catalysts for alkyne metathesis but lead to disappointing results and poor stability in the tungsten series. ¹H,¹⁸³W heteronuclear multiple bond correlation spectroscopy, exploiting a favorable ⁵J‐coupling between the ¹⁸³W center and the peripheral protons on the alkylidyne cap, revealed that these ligands upregulate the Lewis acidity to an extent that the tungstenacyclobutadiene formed in the initial [2+2] cycloaddition step is over‐stabilized and the catalytic turnover brought to a halt. Guided by the ¹⁸³W NMR shifts as a proxy for the Lewis acidity of the central atom and by an accompanying chemical shift tensor analysis of the alkylidyne unit, the ligand design was revisited and a more strongly π‐donating all‐alkoxide ligand prepared. The new expanded chelate complex has a tempered Lewis acidity and outperforms the classical Schrock catalyst, carrying monodentate tert‐butoxy ligands, in terms of rate and functional‐group compatibility.

中文翻译：

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183 W NMR 光谱指导寻找用于炔复分解的烷基钨催化剂。

三芳基硅烷醇盐是用于炔复分解的钼亚烷基催化剂的优先辅助配体，但在钨系列中导致令人失望的结果和较差的稳定性。¹ H, ¹⁸³ W 异核多重键相关光谱，利用¹⁸³ W 中心与烷叉帽上的外围质子之间有利的⁵ J耦合，揭示了这些配体将路易斯酸度上调到一定程度，使得环丁二烯钨在最初形成[2+2]环加成步骤过度稳定并且催化周转停止。以¹⁸³ W NMR 位移作为中心原子路易斯酸度的代表，并通过烷叉单元的化学位移张量分析，重新审视了配体设计，并制备了更强的 π 供体全醇盐配体。新的膨胀螯合物具有缓和的路易斯酸度，并且在速率和官能团相容性方面优于带有单齿叔丁氧基配体的经典Schrock催化剂。