Li Ai-Min, Wang Yi, Downing Domonique O, Chen Fu, Zavalij Peter, Muñoz-Castro Alvaro, Eichhorn Bryan W
Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, 20742, USA.
Grupo de Química Inorgánica y Materiales Moleculares, Facultad de Ingeniería, Universidad Autonoma de Chile, El Llano Subercaseaux 2801, Santiago, Chile.
Chemistry. 2020 May 7;26(26):5824-5833. doi: 10.1002/chem.201905451. Epub 2020 Apr 28.
The icosahedral [M@Pb ] (M=Co(1), Rh(2), Ir(3)) cluster ions were prepared from K Pb and Co(dppe)Cl (dppe=1,2-bis(diphenylphosphino)ethane)/[Rh(PPh ) Cl]/[Ir(cod)Cl] (cod=1,5-cyclooctadiene), respectively, in the presence of 18-crown-6/ 2,2,2-cryptand in ethylenediamine/toluene solvent mixtures. The [K(2,2,2-cryptand)] salt of 1 and the [K(18-crown-6)] salt of 3 were characterized via X-ray crystallography; the ions 1 and 3 are isostructural and isoelectronic to the [Rh@Pb ] (2) ion as well as to the group 10 clusters [M'@Pb ] (M'=Ni, Pd, Pt). The ions are all 26-electron clusters with near perfect icosahedral I point symmetry. Clusters 1-3 show record downfield Pb NMR chemical shifts due to σ-aromaticity of the cluster framework. Calculated and observed Pb NMR chemical shifts and Pb- M J-couplings ( M= Co, Rh, Ir) are in excellent agreement and DFT analysis shows that the variations of Pb NMR chemical shifts for the [M@Pb ] ions (M=Co, Rh, Ir, Ni, Pd, Pt) are mainly governed by the perpendicularly oriented σ component of the chemical shift anisotropy tensor. The laser desorption ionization time-of-flight (LDI-TOF) mass spectra contain the molecular ions as well as several new gas phase clusters derived from the parents. The DFT-minimized structures of these ions are described.
二十面体[M@Pb₁₂]（M = Co(1)、Rh(2)、Ir(3)）簇离子分别由K₄Pb₁₂和Co(dppe)Cl₂（dppe = 1,2 - 双（二苯基膦基）乙烷）/[Rh(PPh₃)₃Cl]/[Ir(cod)Cl]₂（cod = 1,5 - 环辛二烯）在18 - 冠 - 6/2,2,2 - 穴醚存在下，于乙二胺/甲苯混合溶剂中制备而成。通过X射线晶体学对1的[K(2,2,2 - 穴醚)]盐和3的[K(18 - 冠 - 6)]盐进行了表征；离子1和3与[Rh@Pb₁₂] (2)离子以及第10族簇[M'@Pb₁₂]（M' = Ni、Pd、Pt）具有同构和等电子关系。这些离子均为26电子簇，具有近乎完美的二十面体I点对称性。簇1 - 3由于簇框架的σ芳香性，显示出创纪录的低场¹²⁵Pb核磁共振化学位移。计算得到的和观测到的¹²⁵Pb核磁共振化学位移以及¹²⁵Pb - ¹⁹⁵M J耦合（M = Co、¹⁰³Rh、¹⁹³Ir）吻合得非常好，密度泛函理论分析表明，[M@Pb₁₂]离子（M = Co、Rh、Ir、Ni、Pd、Pt）的¹²⁵Pb核磁共振化学位移变化主要由化学位移各向异性张量的垂直取向σ分量决定。激光解吸电离飞行时间（LDI - TOF）质谱包含分子离子以及源自母体的几个新的气相簇。描述了这些离子的密度泛函理论最小化结构。
