Department of Radiochemistry, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
J Am Soc Mass Spectrom. 2018 Dec;29(12):2327-2332. doi: 10.1007/s13361-018-2057-0. Epub 2018 Aug 23.
Ligated tetrapositive metal ions are rare gas-phase species which tend to form complexes with lower charges due to the high 4th ionization energies of metals. We report the observation of tetrapositive Zr(TMPDA) and Zr(TMOGA) complexes in the gas phase by electrospray ionization of Zr(ClO)/TMPDA and Zr(ClO)/TMOGA mixtures. The Zr center in both complexes is coordinated by nine atoms from three neutral diamide ligands forming nine-coordinate twisted tricapped trigonal prismatic geometry on the basis of DFT calculations. Collision-induced dissociation of both complexes resulted in the loss of protonated ligands to form tripositive Zr(TMPDA)(TMPDA-H) and Zr(TMOGA)(TMOGA-H) products which retain the IV oxidation state of zirconium at the cost of charge reduction from 4+ to 3+ of the whole complexes. The very high 4th ionization energy of zirconium (34.34 eV) makes tetrapositive zirconium complex the most challenging tetracation to be stabilized against charge reduction in the gas phase to date. Graphical abstract ᅟ.
配位数为四的正电性金属离子是稀有气相物种，由于金属的第四电离能较高，它们往往会与较低电荷的配体形成配合物。我们通过电喷雾电离 Zr(ClO)/TMPDA 和 Zr(ClO)/TMOGA 混合物，在气相中观察到了四正电性 Zr(TMPDA)和 Zr(TMOGA)配合物。基于 DFT 计算，两个配合物中的 Zr 中心均由三个中性二酰胺配体的九个原子配位，形成九配位扭曲三帽三角棱柱几何构型。两种配合物的碰撞诱导解离均导致质子化配体的丢失，形成三正电性 Zr(TMPDA)(TMPDA-H)和 Zr(TMOGA)(TMOGA-H)产物，其中锆的 IV 氧化态保持不变，但整个配合物的电荷从 4+降低至 3+。锆的第四电离能非常高（34.34 eV），这使得四正电性锆配合物成为迄今为止气相中最难稳定的四价正离子，以防止其电荷降低。
