Harmon-Welch Gabrielle E, Hoefler John C, Trujillo Martha R, Bhuvanesh Nattamai, Bakhmutov Vladimir I, Blümel Janet
Department of Chemistry, Texas A&M University, College Station, Texas 77845-3012, United States.
J Phys Chem C Nanomater Interfaces. 2023 Feb 6;127(6):3059-3066. doi: 10.1021/acs.jpcc.2c07441. eCollection 2023 Feb 16.
Ferrocene and nickelocene do not react with each other in solution; however, the large impact of the paramagnetic component on the ferrocene H NMR signal linewidth and relaxation times has been quantified. Co-crystallization of ferrocene and nickelocene at any ratio from a solvent can be explained with both pure substances crystallizing in the same space group 2/. As a new phenomenon, when a ferrocene single crystal is exposed to polycrystalline nickelocene in the absence of a solvent, the nickelocene migrates into the ferrocene crystal lattice and a mixed crystal is formed that retains its macroscopic shape. This process has been proven visually by cutting the single crystal. Mixing polycrystalline ferrocene with polycrystalline nickelocene at different molar ratios with a mortar and pestle leads to crystalline solid solutions with the corresponding molar ratios of both components. This migration of one organometallic component into an existing crystal lattice of another at ambient temperature in the absence of a solvent has not been described previously. Paramagnetic H solid-state NMR spectroscopy of static and rotating samples of dry ferrocene/nickelocene mixtures at varying ratios is used to prove and quantify the mixing of both metallocenes at the molecular level. A single-crystal X-ray structure of a 50/50 mixed crystal corroborates the NMR results that nickelocene and ferrocene are randomly distributed in the lattice and that the space group 2/ is retained. All ferrocene molecules in the mixed crystal lattice show a broadening of their H wideline signals and residual magic-angle spinning (MAS) lines at ambient temperature. The broadening of the ferrocene signals correlates with the nickelocene content. H relaxation time measurements for the signals of ferrocene in samples with different amounts of nickelocene corroborate the assumption that the signal broadening is due to paramagnetic dipole-dipole relaxation of ferrocene molecules in the vicinity of nickelocene. Spatially separated ferrocene and nickelocene powders in one rotor show the solid-state NMR characteristics of the individual polycrystalline metallocenes. The described formation of solid solutions of metallocenes in the absence of a solvent will open new pathways to homogeneously mixed nanoparticles with desired metal ratios and dual-atom catalysts.
二茂铁和二茂镍在溶液中不发生相互反应；然而，顺磁性成分对二茂铁氢核磁共振信号线宽和弛豫时间的巨大影响已被量化。二茂铁和二茂镍以任何比例从溶剂中共结晶，可以解释为两种纯物质在相同的空间群2/中结晶。作为一种新现象，当二茂铁单晶在无溶剂的情况下暴露于多晶二茂镍时，二茂镍会迁移到二茂铁晶格中并形成保留其宏观形状的混合晶体。通过切割单晶已直观地证明了这一过程。用研钵和研杵将不同摩尔比的多晶二茂铁与多晶二茂镍混合会导致形成具有相应摩尔比的两种组分的结晶固溶体。在无溶剂的环境温度下，一种有机金属成分迁移到另一种现有晶格中，这种情况以前尚未有过描述。使用不同比例的干燥二茂铁/二茂镍混合物的静态和旋转样品的顺磁性氢固态核磁共振光谱来证明和量化两种金属茂在分子水平上的混合。50/50混合晶体的单晶X射线结构证实了核磁共振结果，即二茂镍和二茂铁在晶格中随机分布且空间群2/得以保留。混合晶格中的所有二茂铁分子在环境温度下其氢宽线信号和残余魔角旋转（MAS）线都变宽。二茂铁信号的变宽与二茂镍含量相关。对含有不同量二茂镍的样品中二茂铁信号的氢弛豫时间测量证实了信号变宽是由于二茂铁分子在二茂镍附近的顺磁性偶极-偶极弛豫这一假设。在一个转子中空间分离的二茂铁和二茂镍粉末显示出各个多晶金属茂的固态核磁共振特征。所描述的在无溶剂情况下金属茂固溶体的形成将为具有所需金属比例的均匀混合纳米颗粒和双原子催化剂开辟新途径。
