A multi-dimensional approach combining HPLC, ion mobility and high resolution mass spectrometry for investigating transition metal complexes

Organometallic complexes play a central role in catalysis and medicinal chemistry, yet their analytical characterization via mass spectrometry remains challenging due to their reactivity, susceptibility to fragmentation and the resulting overlapping isotopologue patterns, especially in complex reaction mixtures. Herein, we present a high-performance liquid chromatography ion mobility mass spectrometry workflow for the separation and analysis of group-six metal complexes. Chromatographic separation was combined with variation of electrospray ionization source conditions, allowing fragmentation behavior to be tuned according to specific analytical requirements. Ion mobility spectrometry provided an additional separation dimension that enabled the determination of collision cross sections as molecular descriptors for all investigated complexes. Analysis of the ion mobility data revealed systematic, metal-dependent trends consistent with expected structural differences. These correlations facilitated the assignment of the central metal even for species of low abundance or those lacking characteristic isotopologue patterns. Overall, this work demonstrates that the combination of chromatographic separation and ion mobility-based trend analysis provides a versatile platform for the characterization of organometallic species.