Institute of Applied Synthetic Chemistry, Vienna University of Technology, Vienna, Austria.
Institute of Chemical Technologies and Analytics, Vienna University of Technology, Vienna, Austria.
Rapid Commun Mass Spectrom. 2022 May 30;36(10):e9281. doi: 10.1002/rcm.9281.
Organometallic compounds are becoming increasingly important in their industrial application as catalysts. Mass spectrometry is an essential tool for the structural confirmation of such organometallics. Because the analysis of this class of molecules can be challenging, the ionization behavior and structural confirmation of selected transition metal catalysts are described in this work.
The transition metal catalysts investigated were analyzed using classical vacuum MALDI reflectron TOF-MS as well as intermediate pressure matrix-assisted laser desorption/ionization quadrupole time-of-flight mass spectrometry (MALDI QTOF-MS). Obtained mass spectra were compared with electrospray ionization MS (ESI-MS) already established for organometallic compounds, utilizing a QTOF mass spectrometer here. In addition, various sample preparations, including two selected MALDI matrices (trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenylidene]malononitrile and 2,2':5',2″-terthiophene) with different solvent combinations for MALDI-MS measurements, were investigated in detail with respect to their correct isotope distribution of the molecular ions observed.
All investigated organometallic compounds were successfully identified by vacuum and intermediate pressure MALDI-MS. Accurate masses of ions related to molecular ion species (e.g., [M-Cl] , [M] , and [M + Na] ) could be determined by MALDI QTOF-MS measurements with a mass error of less than ±5 ppm for all compounds. Both investigated MALDI matrices performed equally on both instruments. The impact of the analyte/matrix solvent mixtures turned out to be crucial for a successful analysis of the investigated compounds. In contrast, ESI QTOF-MS yielded masses of ions related to molecular ion species in favorable cases.
The use of MALDI-MS for the structural confirmation of organometallic compounds is still not widely used. Nevertheless, this work showed that this analytical technique does have some benefits. The analysis of neutral catalysts proves to be quite useful, concluding that this technique provides a complement and/or an alternative to ESI-MS.
有机金属化合物作为催化剂在工业应用中变得越来越重要。质谱是对这类有机金属进行结构确证的重要工具。由于分析这类分子具有挑战性，因此本工作描述了选定过渡金属催化剂的离子化行为和结构确证。
使用经典真空 MALDI 反射式飞行时间质谱（TOF-MS）以及中等压力基质辅助激光解吸/电离四极杆飞行时间质谱（MALDI QTOF-MS）分析所研究的过渡金属催化剂。获得的质谱与已经为有机金属化合物建立的电喷雾电离 MS（ESI-MS）进行了比较，这里利用 QTOF 质谱仪进行了比较。此外，详细研究了各种样品制备方法，包括两种选定的 MALDI 基质（反式-2-[3-（4-叔丁基苯基）-2-甲基-2-丙烯基]丙二腈和 2,2':5',2″-三联噻吩）以及用于 MALDI-MS 测量的不同溶剂组合，以研究它们对观察到的分子离子正确同位素分布的影响。
通过真空和中等压力 MALDI-MS 成功地鉴定了所有研究的有机金属化合物。通过 MALDI QTOF-MS 测量，可以确定与分子离子物种（例如[M-Cl]、[M]和[M+Na]）相关的离子的精确质量，所有化合物的质量误差均小于±5 ppm。两种研究的 MALDI 基质在两种仪器上的性能相同。分析物/基质溶剂混合物的影响对于成功分析所研究的化合物至关重要。相比之下，ESI QTOF-MS 在有利的情况下产生与分子离子物种相关的离子的质量。
MALDI-MS 用于有机金属化合物的结构确证的应用还不广泛。然而，本工作表明，这种分析技术确实有一些优势。中性催化剂的分析证明非常有用，这表明该技术提供了对 ESI-MS 的补充和/或替代。
