For soluble complexes, down-or upfield shifting of selected signalsespecially of hydrogen atoms close to the coordinating nitrogen centeris expected. In those cases where the obtained metal complex is less soluble, NMR measurements should reveal a strong depletion up to the complete disappearance of the signals of the ligands. Therefore, an NMR screening combines beneficial aspects for monitoring the complexation of insoluble and soluble complexes. The process allows the indirect detection of insoluble complexes and monitors the progress of the complexation where missing precipitation hinders the direct observation of complexation in standard crystallization experiments.