To gain insights into the fragmentation behavior and the stability of the complexes in the gas phase after electron bombardment, Electron impact mass spectrometry (EI-MS) was performed. Contrary to the findings from the structure validation for all complexes, no m/z value above their respective mononuclear M + peak was found in their respective EI-MS spectra (Figure ). Similar findings for electron impact ionization of dinuclear complexes are known for other TM-precursors shown by Boysen et.al. , which can be explained by relative harsh conditions used in the EI-MS mode where the compound is first evaporated and then ionized by an electron beam. The fragments found with their respective intensities are tabulated in Table . The general intensity consideration of the Mmono + signals occurring under electron ionization resulted in an expected stability trend: while compound III, V and VII revealed very low Mmono + signal intensities between 2% and 8%, three of the amidinates exhibit much higher M + mono signal intensities between 18% and 60%. These findings show the trend, that also under EI-MS conditions, the guanidinates reveal a general lower stability in comparison, while compound III is an exceptionally unstable amidinate. The consideration of other selected signals (Table ) reveals high similarities for the fragmentation behavior of the compounds. For all compounds, relatively low signal intensities for bigger fragments like the ligand cleavage ([M-L] •+ ;[L] •+ ) can be found, while here the prior named stability trend is again observed. One major exception seemed to be in both tert-butyl congeners of the amidinates which exhibited the 100% m/z signal at m/z=378 ([M-Me] •+ ) and m/z=350 ([M-Me] •+ ) for compounds II and IV, respectively. These fragments could originate from the cleavage of a methyl fragment resulting in stabilized charge on the obtained isopropyl group on the respective ligand (fragmentation scheme Figure ). The 100% signals for the other compounds were detected in the range of other small relevant organic fragments (Table ) which furthermore indicate the high decomposition rate in the EI-MS vaporization or ionization chamber. Nevertheless, for all compounds, a peak for the respective ligand cleavage is observed with intensities for the more stable amidinates (I-IV) between 19% and 54% and between 3% and 16% for the measured guanidinates (V, VII). Overall, the molecular ion peaks, the SC-XRD structures and the matching elemental analysis support the successful synthesis and structural identity of the new Mn compounds.