Triphenylphosphine (PPh₃) is a ubiquitous ligand in organometallic chemistry that has been shown to give enhanced ³¹P NMR signals at high magnetic field via a scalar-dominated Overhauser effect dynamic nuclear polarization (OE DNP). However, PPh₃ can only be polarized via DNP in the free form, while the coordinated form is DNP-inactive. Here, we demonstrate the possibility of enhancing the ³¹P NMR signals of coordinated PPh₃ in metal complexes in solution at room temperature by combining Overhauser effect DNP and chemical exchange between the free and coordinated PPh₃ forms. With this method, we successfully obtain ³¹P DNP enhancements of up to 2 orders of magnitude for the PPh₃ ligands in Rh(I), Ru(II), Pd(II), and Pt(II) complexes, and we show that the DNP enhancements can be used to determine the activation energy of the ligand exchange reaction.

中文翻译：

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通过交换介导的奥豪瑟动态核极化 NMR 探测溶液中的均相催化剂和预催化剂

三苯基膦 (PPh ₃ ) 是有机金属化学中普遍存在的配体，已被证明可通过标量主导的奥豪塞效应动态核极化 (OE DNP) 在高磁场下提供增强的³¹ P NMR 信号。然而，PPh ₃只能通过游离形式的 DNP 极化，而配位形式则没有 DNP 活性。在这里，我们证明了通过结合欧沃豪瑟效应 DNP 以及游离和配位 PPh ₃形式之间的化学交换，增强室温溶液中金属配合物中配位 PPh _3的³¹ P NMR 信号的可能性。通过这种方法，我们成功地将Rh(I)、Ru(II)、Pd(II) 和 Pt(II) 配合物中的 PPh _3配体的³¹ P DNP 增强了高达 2 个数量级，并且我们表明DNP 增强可用于确定配体交换反应的活化能。