Proton Sponge Phosphanes: Reversibly Chargeable Ligands for ESI-MS Analysis
Proton Sponge Phosphanes: Reversibly Chargeable Ligands for ESI-MS Analysis
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质子海绵磷烷：用于 ESI-MS 分析的可逆带电配体
DOI：
10.1002/ejic.201100820
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发表时间：
2011
影响因子：
2.3
通讯作者：
Farrer N
中科院分区：
文献类型：
--
作者：
Farrer N
质子海绵磷烷是不寻常的配体，因为它们拥有两个功能截然不同的碱性位点：磷与金属中心结合，而 1,8-双（二甲氨基）萘与质子强烈结合。两个基团都对其目标具有选择性，并且通过控制溶液的 pH 值可以轻松逆转质子的结合。因此，质子海绵磷烷可成为有用的可带电荷配体，用于对其结合的复合物进行电喷雾电离质谱分析。然而，1,8-双（二甲氨基）萘与膦官能化的位置至关重要，并且当二苯基膦处于2-位时，1-二甲氨基可以参与与金属的结合。从保持质子和金属结合分离的角度来看，这种行为是不受欢迎的，我们介绍了一种 4-取代质子海绵膦的有效合成方法，其中两个官能团位于萘环的相对侧。这种预防措施解决了分子作为双齿配体的问题，但在使用配体时仍然需要小心，因为电离途径（例如卤化物解离形成 [M – X]+ 离子和富电子金属配合物氧化形成 [M]·+ ）可能与质子化竞争。
Proton sponge phosphanes are unusual ligands in that they possess two basic sites with very different functions: the phosphorus binds to a metal center, while the 1,8‐bis(dimethylamino)naphthalene binds protons strongly. Both groups are selective for their target, and the binding of the proton iseasily reversible by controlling the pH of the solution. Proton sponge phosphanes therefore make useful chargeable ligands for the purposes of electrospray ionization mass spectrometric analysis of the complexes in which they are bound. However, where the 1,8‐bis(dimethylamino)naphthalene is functionalized with the phosphane is critical, and the 1‐dimethylamino group can become involved in binding to the metal when diphenylphosphane is in the 2‐position. This behavior is undesirable from the point of view of keeping proton and metal binding segregated, and we introduce an efficient synthesis of the 4‐substituted proton sponge phosphane in which the two functional groups are on opposite sides of the naphthalene ring. This precaution solves the problem of the molecule acting as a bidentate ligand, but caution is still needed when using the ligand, because ionization pathways such as halide dissociation to form [M – X]+ions and oxidation of electron‐rich metal complexes to form [M]·+can be competitive with protonation.