This study presents three examples in which the methodological approach of operando UV/vis spectroscopy is demonstrated using both submersible optrodes and the stopped flow/diode array technique. First, the submersible optrode is applied for the monitoring of stoichiometric reactions, that is the hydrogenation of cyclooctadiene (cod) in the rhodium diphosphine complex [Rh(Me-DuPHOS)(cod)] BF(4) (Me-DuPHOS = 1,2-bis(-2,5-dimethyl-phospholano) benzene), which is a typical catalyst precursor in asymmetric hydrogenation. Second, the determination of stability constants for rhodium diphosphine arene complexes is shown. The third example presents UV/vis spectroscopy of zirconium and hafnium complexes with ethylene as a gaseous reaction partner using the stopped flow/diode array technique. (C) 2009 Elsevier B.V. All rights reserved.