Rollover cyclometalation with 2-(2'-pyridyl)quinoline.
Rollover cyclometalation with 2-(2'-pyridyl)quinoline.
复制标题
2-(2-吡啶基)喹啉的翻转环金属化。
作者：
A. Zucca;Diletta Cordeschi;L. Maidich;M. Pilo;Elisabetta Masolo;S. Stoccoro;M. Cinellu;S. Galli
2-(2'-吡啶基)喹啉 L 的翻转环金属化允许合成络合物家族 [Pt(L-H)(X)(L')] 和 [Pt(L*)(X)(L')][BF4]（X = Me, Cl；L' = 中性配体），前者是衍生自配体 L 的 Pt(II) 翻转络合物的第一个例子。配体 L* 是 C,N L 的环金属化、N-质子化异构体，也可以描述为异常远程吡啶基。相应的[Pt(L-H)(Me)(L')]/[Pt(L*)(Me)(L')](+)配合物构成了罕见的Brønsted-Lowry酸碱共轭对。通过核磁共振和紫外可见光谱、循环伏安法和密度泛函理论 (DFT) 方法对获得的物质进行了深入研究，以将不同的化学物理性质与环金属化配体（例如，L 与 bipy 或 L* 与 L）和中性配体（DMSO、CO、PPh3）的性质相关联。通过X射线粉末衍射方法测定了[Pt(L-H)(Me)(PPh3)]、[Pt(L-H)(Me)(CO)]和[Pt(L*)(Me)(CO)][BF4]的晶体结构，后者是第一个被揭示的Pt(II)基质子化翻转配合物的结构。 [Pt(L*)(Me)(PPh3)](+) 在溶液中的异构化通过逆向翻转过程进行，得到相应的加合物 [Pt(L)(Me)(PPh3)](+)，其中 L 充当经典的 N,N 螯合配体。值得注意的是，在文献报道的众多 Pt-C 键质子分解反应中，逆翻转反应是第一个过程，其中 Pt-C（杂芳基）键而不是 Pt-C（烷基）键被裂解。
Rollover cyclometalation of 2-(2'-pyridyl)quinoline, L, allowed the synthesis of the family of complexes [Pt(L-H)(X)(L')] and [Pt(L*)(X)(L')][BF4] (X = Me, Cl; L' = neutral ligand), the former being the first examples of Pt(II) rollover complexes derived from the ligand L. The ligand L* is a C,N cyclometalated, N-protonated isomer of L, and can also be described as an abnormal-remote pyridylene. The corresponding [Pt(L-H)(Me)(L')]/[Pt(L*)(Me)(L')](+) complexes constitute an uncommon Brønsted-Lowry acid-base conjugated couple. The species obtained were investigated in depth through NMR and UV-vis spectroscopy, cyclic voltammetry, and density functional theory (DFT) methods to correlate different chemico-physical properties with the nature of the cyclometalated ligand (e.g., L vs bipy or L* vs L) and of the neutral ligand (DMSO, CO, PPh3). The crystal structures of [Pt(L-H)(Me)(PPh3)], [Pt(L-H)(Me)(CO)] and [Pt(L*)(Me)(CO)][BF4] were determined by X-ray powder diffraction methods, the latter being the first structure of a Pt(II)-based, protonated, rollover complex to be unraveled. The isomerization of [Pt(L*)(Me)(PPh3)](+) in solution proceeds through a retro-rollover process to give the corresponding adduct [Pt(L)(Me)(PPh3)](+), where L acts as a classical N,N chelating ligand. Notably, the retro-rollover reaction is the first process, among the plethora of Pt-C bond protonolysis reactions reported in the literature, where a Pt-C(heteroaryl) bond is cleaved rather than a Pt-C(alkyl) one.